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1

Synthesis of nanocrystalline magnesium aluminate (MgAl 2O 4) spinel powder by the urea–formaldehyde polymer gel combustion route  

Microsoft Academic Search

Nanocrystalline MgAl2O4 spinel powder was synthesized by the urea–formaldehyde (UF) polymer gel combustion route. A transparent gel formed from magnesium nitrate, aluminium nitrate and UF after drying underwet self-sustained combustion when initiated with a burning splinter. The combustion product on calcinations at 850°C formed MgAl2O4 spinel. Calcination of the combustion product resulted in particle coarsening. The powder obtained by planetary

K. Prabhakaran; D. S. Patil; R. Dayal; N. M. Gokhale; S. C. Sharma

2009-01-01

2

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

SciTech Connect

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.

Biswas, M. [Central Glass and Ceramic Research Institute, Kolkata 700 032 (India)] [Central Glass and Ceramic Research Institute, Kolkata 700 032 (India); Bandyopadhyay, S., E-mail: sbando@cgcri.res.in [Central Glass and Ceramic Research Institute, Kolkata 700 032 (India)

2012-03-15

3

[Inhibition of chlorobenzene formation via various routes during waste incineration by ammonium sulfate and urea].  

PubMed

Chlorobenzene (CBz) is the precursor of polychlorinated dibenzo-p-dioxins/polychlorinated dibenzofurans (PCDD/Fs) generated in the processes of waste incineration, and it is regarded as a good indicator of PCDD/Fs for realizing PCDD/Fs online monitoring, moreover, pentachlorobenzene (PeCBz) and Hexachlorobenzene (HxCBz) belong to Persistent Organic Pollutants (POPs). However, the emission control of CBz in waste incineration does not attract enough attention, so this study focused on the inhibition of the 3 CBz formation routes in waste combustion by ammonium sulfate and urea, including CB formation from fly ash, CB formation from 1,2-dichlorobenzene (1,2-DiCBz) and the combustion of model medical waste. The results showed that both ammonium sulfate and urea reduced CBz yield during these three thermal processes. For instance, the inhibition rates of tetrachlorobenzene (TeCBz), PeCBz and HxCBz were 66.8%, 57.4% and 50.4%, respectively, when 1% urea was co-combusted with medical waste. By comparing the effect of ammonium sulfate and urea on CBz formation by three routes, urea was considered as a comparatively stable inhibitor for CBz. PMID:24720230

Yan, Mi; Qi, Zhi-Fu; Li, Xiao-Dong; Hu, Yan-Jun; Chen, Tong

2014-01-01

4

Ternary metal nitrides by the urea route  

SciTech Connect

Interstitial molybdenum ternary nitrides, M {sub n}Mo{sub 3}N (M = Fe and Co, n = 3; M = Ni, n = 2), can be obtained by heating the molybdate precursors, FeMoO{sub 4}, CoMoO{sub 4} and NiMoO{sub 4} with urea in the 1:12 molar ratio in the 900-1000 deg. C range. Fe{sub 3}Mo{sub 3}N and Co{sub 3}Mo{sub 3}N are obtained in pure form. The nickel nitride has the composition Ni{sub 2}Mo{sub 3}N and therefore is in admixture with nickel. All the nitrides have been characterized by various physical methods.

Gomathi, A. [Chemistry and Physics Materials Unit and CSIR Centre of Excellence in Chemistry, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur P.O., Bangalore, Karnataka 560 064 (India)]. E-mail: gomathi@jncasr.ac.in

2007-05-03

5

Synthesis of aluminum nitride nanoparticles by a facile urea glass route and influence of urea/metal molar ratio  

NASA Astrophysics Data System (ADS)

Attention toward nanosized aluminum nitride (AlN) was rapidly increasing due to its physical and chemical characteristics. In this work, nanocrystalline AlN particles were prepared via a simple urea glass route. The effect of the urea/metal molar ratio on the crystal structure and morphology of nanocrystalline AlN particles was studied using X-ray powder diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). The results revealed that the morphology and the crystal structure of AlN nanoparticles could be controlled by adjusting the urea/metal ratio. Furthermore, a mixture of Al2O3 and h-AlN was detected at the urea/metal molar ratio of 4 due to the inadequate urea content. With increasing the molar ratio, the pure h-AlN was obtained. In addition, the nucleation and growth mechanisms of AlN nanocrystalline were proposed.

Gao, Zhifang; Wan, Yizao; Xiong, Guangyao; Guo, Ruisong; Luo, Honglin

2013-09-01

6

A simple urea-based route to ternary metal oxynitride nanoparticles  

NASA Astrophysics Data System (ADS)

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 2N ( M=Ca, Sr or Ba), MNbO 2N ( M=Sr or Ba), LaTiO 2N and SrMoO 3-xN x have been prepared successfully. The oxynitrides so obtained were generally in the form of nanoparticles, and were characterized by various physical techniques.

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

2009-01-01

7

A simple urea-based route to ternary metal oxynitride nanoparticles  

SciTech Connect

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.

Gomathi, A.; Reshma, S. [Chemistry and Physics of Materials Unit, DST Unit on Nanoscience and CSIR Centre of Excellence in Chemistry, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur P.O., Bangalore 560064 (India); Rao, C.N.R. [Chemistry and Physics of Materials Unit, DST Unit on Nanoscience and CSIR Centre of Excellence in Chemistry, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur P.O., Bangalore 560064 (India)], E-mail: cnrrao@jncasr.ac.in

2009-01-15

8

Novel route for layered double hydroxides preparation by enzymatic decomposition of urea  

NASA Astrophysics Data System (ADS)

This study presents a new route for the preparation of a series of layered double hydroxide materials with controlled textural properties. It concerns the biogenesis of hydrotalcite like phases by Jack bean urease through the enzymatic decomposition process of urea. Different conditions of LDH biogenesis are investigated (urease activity, urea concentration). A comparative study with the precipitation method based on the thermal decomposition of urea (90 °C) is conducted in order to asses the effect of the various urea hydrolysis conditions (kinetic, temperature) and the presence of enzyme in the reaction medium on the structural and textural properties of the as prepared LDH materials. Mechanisms of formation of the LDH phases for both synthesis processes are discussed on basis of their pH control. The PXRD and SEM analysis of samples prepared by the thermal process evidence higher crystallinity and greater particle sizes than LDH obtained in mild biogenic conditions. In the latter case, presence of urease or effect of some M(II) metals may inhibit the crystallization.

Vial, S.; Prevot, V.; Forano, C.

2006-05-01

9

Synthesis of Nanoscale Nd-Doped Ceria Via Urea-Formaldehyde Combustion Method  

NASA Astrophysics Data System (ADS)

Nanocrystalline neodymium-doped ceria solid solutions with Nd3+ concentrations varying from 4 to 20 mol pct have been synthesized by gel combustion method, using urea-formaldehyde as fuel for Nd doping. The combustion reaction is explained through differential scanning calorimetry (DSC)-differential thermogravimetric analysis (TGA), whereas the synthesized materials are characterized through X-ray diffractometry (XRD), field-emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). The phase obtained from the exothermic reaction contains Nd-substituted CeO2. The deviation of the lattice parameter from Vegard's law and the decrease in crystallite size with dopant concentration has been explained. The as-synthesized particles are largely nanoporous single crystallites, existing in loosely held spherical-shaped agglomerates. The size of the agglomerates increases with increasing dopant content. High-resolution TEM (HRTEM) reveals the fact that the unit cells are strained.

Biswas, M.; Bandyopadhyay, S.

2013-11-01

10

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

PubMed

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

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

2010-01-15

11

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

SciTech Connect

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

Biswas, M. [Ceramic Division, Naval Materials Research Laboratory, Defence Research and Development Organization, Shil Badlapur Road, Anandnagar P.O., Addl. Ambernath, Thane 421 506 (India); Prabhakaran, K. [Ceramic Division, Naval Materials Research Laboratory, Defence Research and Development Organization, Shil Badlapur Road, Anandnagar P.O., Addl. Ambernath, Thane 421 506 (India)]. E-mail: kp2952002@yahoo.co.uk; Gokhale, N.M. [Ceramic Division, Naval Materials Research Laboratory, Defence Research and Development Organization, Shil Badlapur Road, Anandnagar P.O., Addl. Ambernath, Thane 421 506 (India); Sharma, S.C. [Ceramic Division, Naval Materials Research Laboratory, Defence Research and Development Organization, Shil Badlapur Road, Anandnagar P.O., Addl. Ambernath, Thane 421 506 (India)

2007-04-12

12

Effects of synthetic routes of Fe-urea complex on the synthesis of ?-Fe 2O 3 nanopowder  

NASA Astrophysics Data System (ADS)

Maghemite (?-Fe 2O 3) nanopowder was prepared by the thermal decomposition of Fe-urea complex ([Fe(CON 2H 4) 6](NO 3) 3) that was synthesized by various routes including wet and dry synthetic methods. Then the effects of synthetic routes of the [Fe(CON 2H 4) 6](NO 3) 3 on resulting iron oxide crystalline phases and their magnetic properties have been studied using X-ray powder diffraction (XRD) and magnetic measurements. The result of XRD shows that the iron oxide crystalline phases are strongly dependent on the synthetic routes of the [Fe(CON 2H 4) 6](NO 3) 3. When [Fe(CON 2H 4) 6](NO 3) 3 is synthesized in ethanol, thermal decomposition of the compound results in pure ?-Fe 2O 3. When [Fe(CON 2H 4) 6](NO 3) 3 is synthesized either by an aqueous synthetic method or by a dry synthetic method, however, thermal decomposition of the compound results in mixed phases of ?-Fe 2O 3 and ?-Fe 2O 3. Magnetic measurements show that resulting iron oxide nanopowder exhibits a ferromagnetic characteristic with a maximum saturation magnetization (Ms) of 69.0 emu/g for the pure ?-Fe 2O 3 nanopowder.

Asuha, S.; Zhao, S.; Jin, X. H.; Hai, M. M.; Bao, H. P.

2009-08-01

13

Synthesis of Mg 1? x Co x Al 2O 4 blue pigments via combustion route  

Microsoft Academic Search

MgAl2O4 was successfully used as crystalline host network for the synthesis of cobalt-based blue ceramic pigments. Different compositions of Mg1?xCoxAl2O4 (x=0.1–0.3) powders have been prepared by the combustion reaction of corresponding metal nitrates with mixtures of urea and ?-alanine. The resultant powders were characterized by means of XRD, TG-DTA, EDAX, SEM, BET surface area, diffuse reflectance spectrometry and CIEL?a?b? color

Robert Iano?; Radu Laz?u; Paul Barvinschi

2011-01-01

14

Application of Urea Based Selective Non-Catalytic Reduction of Nitric Oxide in the Combustion Effluent Containing Low Concentration of NOx  

Microsoft Academic Search

Selective Non-Catalytic Reduction (SNCR) of Nitric Oxide has been studied experimentally using commercial grade of urea in a pilot-scale diesel fired tunnel furnace. The furnace simulated small-scale combustion systems such as low capacity boiler, hot water heater, oil heater etc., where the operating temperature is in the range of about 900 to 1300 K. The experiment was conducted with low

Khandoker Abul Hossain; Mohammad Nazri Mohd. Jaafar

15

Route to chaos for combustion instability in ducted laminar premixed flames  

NASA Astrophysics Data System (ADS)

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.

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

2012-06-01

16

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

PubMed

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. PMID:22757536

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

2012-06-01

17

Microstructure and mechanical properties of gamma TiAl based alloys produced by combustion synthesis + compaction route  

Microsoft Academic Search

Microstructure and mechanical properties of ?-TiAl alloy with the chemical composition Ti–48Al–2Cr–2Nb (at.%) have been investigated. The alloy was prepared in one step using a combustion synthesis+compaction process, where the synthesis and the shaping take place at the same time. Two different combustion routes were used: forced self-propagating high-temperature synthesis+compaction (FSHS+C) and thermal explosion+compaction (TE+C).Fully lamellar microstructure was obtained in

I. Agote; J. Coleto; M. Gutiérrez; A. Sargsyan; M. García de Cortazar; M. A. Lagos; I. P. Borovinskaya; A. E. Sytschev; V. L. Kvanin; N. T. Balikhina; S. G. Vadchenko; K. Lucas; A. Wisbey; L. Pambaguian

2008-01-01

18

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

SciTech Connect

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.

Gomathi, A. [Chemistry and Physics of Materials Unit, CSIR Centre of Excellence in Chemistry, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur P.O., Bangalore 560064 (India); Rao, C.N.R. [Chemistry and Physics of Materials Unit, CSIR Centre of Excellence in Chemistry, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur P.O., Bangalore 560064 (India)]. E-mail: cnrrao@jncasr.ac.in

2006-05-25

19

Synthesis and characterization of Ni x Mg 1? x Al 2O 4 nano ceramic pigments via a combustion route  

Microsoft Academic Search

MgAl2O4 was successfully used as a crystalline host network for the synthesis of nickel-based nano cyan refractory ceramic pigments. Different compositions of NixMg1?xAl2O4 (0.1?x?0.8) powders have been prepared by using a low temperature combustion reaction (LTCR) of the corresponding metal nitrates with urea (U) as a fuel at 300°C in an open air furnace. The as-synthesized samples were characterized by

I. S. Ahmed; H. A. Dessouki; A. A. Ali

2011-01-01

20

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

PubMed

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

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

2014-10-15

21

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

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.

Chang, Ying [Department of Materials, College of Chemical and Environment Engineering, Hubei University of Technology, Wuhan, Hubei 430068 (China)] [Department of Materials, College of Chemical and Environment Engineering, Hubei University of Technology, Wuhan, Hubei 430068 (China); Dong, Shijie, E-mail: dongsjsj@163.com [School of Mechanical Engineering, Hubei University of Technology, Wuhan, Hubei 430068 (China)] [School of Mechanical Engineering, Hubei University of Technology, Wuhan, Hubei 430068 (China); Wang, Huihu [School of Mechanical Engineering, Hubei University of Technology, Wuhan, Hubei 430068 (China)] [School of Mechanical Engineering, Hubei University of Technology, Wuhan, Hubei 430068 (China); Du, Kuanhe; Zhu, Qingbiao [Department of Materials, College of Chemical and Environment Engineering, Hubei University of Technology, Wuhan, Hubei 430068 (China)] [Department of Materials, College of Chemical and Environment Engineering, Hubei University of Technology, Wuhan, Hubei 430068 (China); Luo, Ping [School of Mechanical Engineering, Hubei University of Technology, Wuhan, Hubei 430068 (China)] [School of Mechanical Engineering, Hubei University of Technology, Wuhan, Hubei 430068 (China)

2012-03-15

22

Structure and magnetic properties of NiFe2O4 nanoferrite prepared by chemical combustion route  

NASA Astrophysics Data System (ADS)

Structure and magnetic properties of NiFe2O4 (NF) nanoferrite have been studied with annealing temperature. NF nanoferrites were prepared by a chemical combustion route. The X-ray diffraction (XRD) shows minor extra peaks of NF at 400 °C. However, spinel ferrite structure has been observed with higher annealing 500-700 °C. The average particles size is measured using Scherer's relation and also by scanning electron microscopy. The magnetic measurements show saturation magnetization (Ms) 44.95, 38.83, 45.26 emu/g, respectively, with 500, 600 and 700 °C.

Singh, Sukhdeep; Verma, Kuldeep Chand; Kotnala, R. K.; Ralhan, N. K.

2011-12-01

23

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

PubMed

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

Kim, Sang Woo; Jung, Young Mi

2007-11-01

24

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

SciTech Connect

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 studies of spark-ignition engine operation on H{sub 2}-NG and numerical simulation of the impact of hydrogen blending on the physical and chemical processes within the engine; and (2) Examination of hydrogen-assisted combustion in advanced compression-ignition engine processes. To that end, numerical capabilities were applied to the study of hydrogen assisted combustion and experimental facilities were developed to achieve the project objectives.

Andre Boehman; Daniel Haworth

2008-09-30

25

Chemical synthesis of nanocrystalline magnesium aluminate spinel via nitrate–citrate combustion route  

Microsoft Academic Search

Nanocrystalline magnesium aluminate spinel (MgAl2O4) was synthesized using metal nitrates, citric acid and ammonium solutions. The precursor and the calcined powders at different temperatures were characterized by X-ray diffraction (XRD), simultaneous thermal analysis (STA), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The combustion mechanism was also studied by a quadrupole mass spectrometer (QMS)

Ali Saberi; Farhad Golestani-Fard; Hosein Sarpoolaky; Monika Willert-Porada; Thorsten Gerdes; Reinhard Simon

2008-01-01

26

Combustion  

NASA Astrophysics Data System (ADS)

The process whereby a substance is combined with oxygen with the production of heat. Burning is a familiar example of this process. The energy required to propel chemical rockets is provided by the combustion of fuel with an oxidant at very high temperatures. A common oxidant is liquid oxygen (often denoted by LOX). Others include hydrogen peroxide and nitrogen tetroxide....

Murdin, P.

2000-11-01

27

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

PubMed

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 ?-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

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

28

UREA INFRASTRUCTURE FOR UREA SCR NOX REDUCTION  

SciTech Connect

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

Bunting, Bruce G.

2000-08-20

29

Physical and magnetic properties of highly aluminum doped strontium ferrite nanoparticles prepared by auto-combustion route  

NASA Astrophysics Data System (ADS)

Highly Al3+ ion doped nanocrystalline SrFe12-xAlxO19 (0?x?12), were prepared by the auto-combustion method and heat treated in air at 1100 °C for 12 h. The phase identification of the powders performed using x-ray diffraction show presence of high-purity hexaferrite phase and absence of any secondary phases. With Al3+ doping, the lattice parameters decrease due to smaller Al3+ ion replacing Fe3+ ions. Morphological analysis performed using transmission electron microscope show growth of needle shaped ferrites with high aspect ratio at Al3+ ion content exceeding x?2. Al3+ substitution modifies saturation magnetization (MS) and coercivity (HC). The room temperature MS values continuously reduced while HC value increased to a maximum value of 18,100 Oe at x=4, which is an unprecedented increase (˜321%) in the coercivity as compared to pure Sr-Ferrite. However, at higher Al3+ content x>4, a decline in magnetization and coercivity has been observed. The magnetic results indicate that the best results for applications of this ferrite will be obtained with an iron deficiency in the stoichiometric formulation.

Luo, H.; Rai, B. K.; Mishra, S. R.; Nguyen, V. V.; Liu, J. P.

2012-08-01

30

Water and urea transport in renal microvillus membrane vesicles  

SciTech Connect

Light scattering was used to measure the water and urea permeability of brush border membrane vesicles (BBMV) isolated from rabbit renal cortex. In stop-flow experiments, exposure of BBMV to a 200 mM inwardly directed mannitol gradient gave a monophasic time course of decreasing BBMV volume corresponding to an osmotic water permeability (Pf) of 1.1 X 10(-2) cm/s at 37 degrees C. The temperature dependence of Pf was biphasic with delta H = 2 kcal/mol for T less than 33 degrees C and delta H = 14 kcal/mol for T greater than 33 degrees C. A 200 mM inwardly directed urea gradient gave a biphasic time course of BBMV volume due to rapid water efflux followed by slower urea influx with urea permeability (Purea) of 2.4 X 10(-6) cm/s. Preincubation of BBMV with increasing (urea) reversibly inhibited both urea flux and thiourea flux according to a single-site inhibition model, suggesting a saturable urea carrier. Comparison of BBMV Pf and Purea with proximal tubule transepithelial water and urea transport rates suggests that the permeability of the tubular apical membrane (BBMV) is high enough to support a transcellular route for both osmotic water and urea transport.

Verkman, A.S.; Dix, J.A.; Seifter, J.L.

1985-05-01

31

Flash synthesis of Li2TiO3 powder by microwave-induced solution combustion  

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

32

Detection of Interstellar Urea  

NASA Astrophysics Data System (ADS)

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 to systematically determine the credibility of detections of weaker signals from new and larger interstellar molecules.

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

33

Chemiresistor urea sensor  

DOEpatents

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.

Glass, Robert S. (Livermore, CA) [Livermore, CA

1997-01-01

34

Quinine and Urea  

NSDL National Science Digital Library

The WebWare molecules of the month are discussed in two laboratory articles in this issue. Quinine is studied in the article "A Fluorimetric Approach to Studying the Effects of Ionic Strength on Reaction Rates: An Undergraduate Steady-State Fluorescence Laboratory Experiment" by Stephen W. Bigger, Peter J. Watkins, and Bruce Verity. Urea, a typical protein denaturant, is used as a cosolvent in the article "Transfer Free Energy and the Hydrophobic Effect" by Joseph M. Serafin.

35

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

SciTech Connect

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}.

Aruna, S.T. [Surface Engineering Division, National Aerospace Laboratories, Post Bag No. 1779, Bangalore 560017 (India); Kini, N.S. [Chemistry and Physics of Materials Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur P.O., Bangalore 560064 (India)], E-mail: nagesh.kini@gmail.com; Rajam, K.S. [Surface Engineering Division, National Aerospace Laboratories, Post Bag No. 1779, Bangalore 560017 (India)

2009-04-02

36

Chemiresistor urea sensor  

DOEpatents

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.

Glass, R.S.

1997-12-16

37

Synthesis of ?-TiAl by thermal explosion + compaction route: Effect of process parameters and post-combustion treatment on product microstructure  

Microsoft Academic Search

In previous works, we suggested a method for the production of ?-TiAl alloys. This method consists of three main stages: thermal\\u000a explosion + compaction, thermal treatment, and hot isostatic pressing (HIP). This processing route shows encouraging results\\u000a in density, microstructure, and mechanical properties. In this work, the effect of some parameters of the thermal explosion\\u000a + compaction process on the

M. A. Lagos; I. Agote; M. Gutiérrez; A. Sargsyan; L. Pambaguian

2010-01-01

38

Dicarboxylic Acid-Urea Complexes.  

National Technical Information Service (NTIS)

A study of the reaction of several acids with urea resulted in a series of compounds of varying stoichiometry and structure. The acids having the structure HO2C(CH2)nCO2H produced saltlike compounds with urea when n = 0 and 1 and H-bonded complexes for n ...

J. Radell B. W. Brodman J. J. Domanski

1966-01-01

39

Structural, optical and dielectric studies of NixZn1-xFe2O4 prepared by auto combustion route  

NASA Astrophysics Data System (ADS)

NixZn1-xFe2O4 (0?x?1) powders were synthesised by the auto combustion method. The derived samples show well defined peaks of cubic spinal structure with space group Fd3m. The lattice parameter calculated increased from 0.8372 nm to 0.8429 nm with raise of Zn content. The average crystallite sizes were determined by using Debye-Scherer method and found to be in the range of 18-23 nm. Microstructural analyses show the regular and uniform grain morphology. Raman analyses demonstrated that the peaks have symmetric and asymmetric stretching as well as symmetric bending. Fourier transform infrared spectroscopy was used to investigate the structure and shows the changes in the tetrahedral and octahedral bond stretching. Photoluminescence measurements indicated intense emission in the wavelength range lie in blue-green region. The composition with x=0.2 showed highest intensity and explained on the basis of disordered cluster model. Dielectric analyses showed frequency sensitive behaviour in the low frequency region and frequency independent characteristics at high frequency side. The composition with x=0.2 showed highest dielectric constant and lowest dielectric loss in the studied frequency range. The ac conductivity showed a power law behaviour and conduction is explained on the basis of hoping mechanism.

Mohit, Kumar; Rout, S. K.; Parida, S.; Singh, G. P.; Sharma, S. K.; Pradhan, S. K.; Won Kim, Ill

2012-03-01

40

Urea Concentration and Haemodialysis Dose  

PubMed Central

Background. Dialysis dose is commonly defined as a clearance scaled to some measure of body size, but the toxicity of uraemic solutes is probably associated more to their concentrations than to their clearance. Methods. 619 dialysis sessions of 35 patients were modified by computer simulations targeting a constant urea clearance or a constant urea concentration. Results. Urea generation rate G varied widely in dialysis patients, rather independently of body size. Dialysing to eKt/V 1.2 in an unselected patient population resulted in great variations in time-averaged concentration (TAC) and average predialysis concentration (PAC) of urea (5.9–40.2 and 8.6–55.8?mmol/L, resp.). Dialysing to equal clearance targets scaled to urea distribution volume resulted in higher concentrations in women. Dialysing to the mean HEMO-equivalent TAC or PAC (17.7 and 25.4?mmol/L) required extremely short or long treatment times in about half of the sessions. Conclusions. The relation between G and V varies greatly and seems to be different in women and men. Dialysing to a constant urea concentration may result in unexpected concentrations of other uraemic toxins and is not recommended, but high concentrations may justify increasing the dose despite adequate eKt/V, std?EKR, or std?K/V.

Vartia, Aarne

2013-01-01

41

Combustion synthesis of calcium aluminates  

SciTech Connect

Commercial calcium aluminate cements for refractory use are known to contain various phases, the hydration behavior of which is interdependent and not fully understood. Hydration studies normally require that pure oxides be synthesized. Solid-state synthesis of single aluminates requires high temperatures and full conversion is not guaranteed. Moreover, it is difficult to obtain a compositionally homogeneous product with this method. The present work discusses a straightforward combustion synthesis technique to prepare submicron calcium aluminates using the corresponding metal nitrates-urea mixtures, at low temperature and short reaction times. The effect of the ratio oxidizer/fuel in the redox mixture was investigated, namely, to find out if urea contents below stoichiometry were enough to trigger the explosive combustion of the fuel and the subsequent decomposition of the salts, and how that ratio affected the phase formation and the characteristics, e.g., morphology and grain size, of the powder produced.

Fumo, D.A.; Segadaes, A.M. [Univ. of Aveiro (Portugal). Dept. Ceramics and Glass Engineering] [Univ. of Aveiro (Portugal). Dept. Ceramics and Glass Engineering; Morelli, M.R. [Federal Univ. Sao Carlos, Sao Paulo (Brazil). Dept. of Materials Engineering] [Federal Univ. Sao Carlos, Sao Paulo (Brazil). Dept. of Materials Engineering

1996-10-01

42

Contact allergy to diazolidinyl urea (Germall II).  

PubMed

4 cases of contact allergy to diazolidinyl urea (Germall II) in a "hypoallergenic" brand of cosmetics are described. 2 patients sensitized by these cosmetics were not allergic to formaldehyde. 2 other patients already sensitive to formaldehyde had exacerbations of dermatitis due to diazolidinyl urea. The following tentative conclusions were drawn. (i) Contact allergy to diazolidinyl urea may or may not be due to formaldehyde sensitivity. (ii) Patients allergic to formaldehyde may suffer contact allergic reactions from the use of cosmetics containing diazolidinyl urea. (iii) Patients sensitized to diazolidinyl urea may cross-react to imidazolidinyl urea and vice-versa. (iv) It is suggested that the sensitizing potential of diazolidinyl urea is greater than that of imidazolidinyl urea. (v) Aq. solutions may be preferable to pet. for patch testing with diazolidinyl urea. PMID:3378427

de Groot, A C; Bruynzeel, D P; Jagtman, B A; Weyland, J W

1988-04-01

43

Acute urea toxicity in sheep.  

PubMed Central

Twenty-seven sheep were assigned to three groups in order to study acute urea toxicity. Groups I, II and III were dosed with 0.5, 0.6 annd 0.75 g/kg of urea, respectively. The mean survival times were 165, 109 and 60 minutes, respectively. The following clinical signs such as pronounced muscle fasciculation, trembling, grinding teeth, ataxia, lateral recumbency, bloating, regurgitation, hyperesthesia, mydriasis and convulsions were observed. Anuria and lack of salivation were also present. The primary cause of death in this study was due to respiratory arrest and not cardiovascular collapse. Plasma examinations showed a marked increase in glucose, ammonia and urea levels but no change in ketone body concentration.

Edjtehadi, M; Szabuniewicz, M; Emmanuel, B

1978-01-01

44

Urea Biosynthesis Using Liver Slices  

ERIC Educational Resources Information Center

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)

Teal, A. R.

1976-01-01

45

Molecular Structure of Urea nitrate  

NSDL National Science Digital Library

Urea nitrate is a plastic explosive used for the charge on a nuclear weapon or as a component of a non-nuclear high explosive. It can also be used as a catalyst in Diels-Alder reactions of aromatic amines. It is favored by amateur terrorists because it is fairly easily derived from urea fertilizers or made by combining nitric and uric acids. Nitric acid can be found as waste from several industrial processes, while urea can be found as biological waste from most animals (in the form of urine). Thus, it provides similar explosive power, but lower cost, as TNT. Additionally, it is quite stable, with low friction and shock sensitivity, making it somewhat stable to work with, but also causing it to require an additional more unstable chemical detonator, called a booster, for use as a high explosive. However, in use as an industrial explosive, urea nitrate is used as a sensitizer to a less reactive fuel. It was the main component of the explosive used in the 1993 bombing of the World Trade Center.

2002-09-23

46

40 CFR 721.9892 - Alkylated urea.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 2013-07-01 false Alkylated urea. 721.9892 Section 721.9892 ...Chemical Substances § 721.9892 Alkylated urea. (a) Chemical substance and significant...substance identified generically as an alkylated urea (PMN P-93-1649) is subject to...

2013-07-01

47

Urea kinetic modeling for CRRT.  

PubMed

Urea kinetic modeling (UKM) for dialysis quantification and prescription, although widely used in chronic renal failure (CRF), has been largely absent in the acute setting. A quantitative approach to prescription of continuous renal replacement therapies (CRRTs) for acute renal failure (ARF) based on UKM is presented. For patients with a relatively constant urea generation rate, G, who are receiving a fixed dose of CRRT, blood urea nitrogen (BUN) falls in an exponential fashion, approaching a plateau level after 3 to 4 days of continuous treatment. The CRRT clearance, K, necessary to achieve a desired plateau value of BUN, Cgoal, may be computed as G/Cgoal x K for all but predilutional CRRT modalities may be calculated as equal to the effluent (dialysate plus ultrafiltrate) flow rate from the filter. Urea mass balance equations are proposed for the determination of patient G value either during the pretreatment rise in BUN or during the decline in BUN with CRRT. In the absence of a reliable estimate of patient G, a reasonable CRRT starting prescription is to set the filter effluent rate in liters per hour (approximately K) to 1.2 times the patient's body weight in kilograms divided by the desired Cgoal in milligrams per deciliter. This relationship assumes moderate hypercatabolism (normalized protein catabolic rate = 2.0 g/kg/d) and patient urea distribution volume equal to 60% of body weight. For Cgoal = 60 mg/dL, this reduces to an easily remembered formula for K (in L/hr) of twice the patient's body weight divided by 100. PMID:9372972

Garred, L; Leblanc, M; Canaud, B

1997-11-01

48

The SLC14 gene family of urea transporters  

Microsoft Academic Search

Carrier-mediated urea transport allows rapid urea movement across the cell membrane, which is particularly important in the process of urinary concentration and for rapid urea equilibrium in non-renal tissues. Urea transporters mediate passive urea uptake that is inhibited by phloretin and urea analogues. Facilitated urea transporters are divided into two classes: (1) the renal tubular\\/testicular type of urea transporter, UT-A1

Chairat Shayakul; Matthias A. Hediger

2004-01-01

49

Predictive model for segmented poly(urea)  

NASA Astrophysics Data System (ADS)

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.

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

2012-08-01

50

Optical and EPR studies of Gd2Zr2O7 phosphors prepared via solution combustion method  

NASA Astrophysics Data System (ADS)

Phosphor powder of Gd2Zr2O7 has been prepared by the urea combustion route. Phase evolution of the synthesized powder is determined by X-ray diffraction (XRD) technique. The structural environment between the Gd3+ and the zirconium oxide lattice has been investigated using electron paramagnetic resonance (EPR), diffuse reflectance and photoluminescence (PL) studies. The EPR spectrum of Gd2Zr2O7 phosphor exhibits a broad and intense signal at g?2.0 and this has been attributed to Gd3+ ions in octahedral symmetry with strong dipolar interactions between Gd3+ ions. The intensity of the spectrum increases with temperature lowering from 296 to 110 K following the usual Boltzmann law. The g value is invariant with temperature variation. The diffuse reflectance spectrum exhibits two sharp and weak bands characteristic of Gd3+ ions in octahedral symmetry. The photoluminescence spectrum exhibits several bands characteristic of Gd3+ ions in octahedral symmetry.

Singh, Vijay; Sivaramaiah, Gobburu; Rao, J. L.; Hwan Kim, Sang

2013-05-01

51

Urea biosensor for hemodialysis monitoring  

DOEpatents

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.

Glass, R.S.

1999-01-12

52

Urea biosensor for hemodialysis monitoring  

DOEpatents

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.

Glass, Robert S. (Livermore, CA) [Livermore, CA

1999-01-01

53

Combustion noise  

NASA Technical Reports Server (NTRS)

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.

Strahle, W. C.

1977-01-01

54

Carbolithiation of N-alkenyl ureas and N-alkenyl carbamates  

PubMed Central

Summary N-Alkenyl ureas and N-alkenyl carbamates, like other N-acyl enamines, are typically nucleophilic at their ?-carbon. However, by incorporating an ?-aryl substituent, we show that they will also undergo attack at the ?-carbon by organolithium nucleophiles, leading to the products of carbolithiation. The carbolithiation of E and Z N-alkenyl ureas is diastereospecific, and N-tert-butoxycarbonyl N-alkenyl carbamates give carbolithiation products that may be deprotected in situ to provide a new connective route to hindered amines.

Lefranc, Julien; Minassi, Alberto

2013-01-01

55

Transcriptional Responses of Uropathogenic Escherichia coli to Increased Environmental Osmolality Caused by Salt or Urea  

PubMed Central

Uropathogenic Escherichia coli (UPEC) is the most common causative agent of urinary tract infections in humans. The majority of urinary infections develop via ascending route through the urethra, where bacterial cells come in contact with human urine prior to reaching the bladder or kidneys. Since urine contains significant amounts of inorganic ions and urea, it imposes osmotic and denaturing stresses on bacterial cells. In this study, we determined the transcriptional adaptive responses of UPEC strain CFT073 to the presence of 0.3 M NaCl or 0.6 M urea in the growth medium. The cell responses to these two osmolytes were drastically different. Although most of the genes of the osmotically inducible regulon were overexpressed in medium with salt, urea failed to stimulate osmotic stress response. At the same time, UPEC colonization genes encoding type 1 and F1C fimbriae and capsule biosynthesis were transcriptionally induced in the presence of urea but did not respond to increased salt concentration. We speculate that urea can potentially be sensed by uropathogenic bacteria to initiate infection program. In addition, several molecular chaperone genes were overexpressed in the presence of urea, whereas adding NaCl to the medium led to an upregulation of a number of anaerobic metabolism pathways.

Withman, Benjamin; Gunasekera, Thusitha S.; Beesetty, Pavani; Agans, Richard

2013-01-01

56

Transcriptional responses of uropathogenic Escherichia coli to increased environmental osmolality caused by salt or urea.  

PubMed

Uropathogenic Escherichia coli (UPEC) is the most common causative agent of urinary tract infections in humans. The majority of urinary infections develop via ascending route through the urethra, where bacterial cells come in contact with human urine prior to reaching the bladder or kidneys. Since urine contains significant amounts of inorganic ions and urea, it imposes osmotic and denaturing stresses on bacterial cells. In this study, we determined the transcriptional adaptive responses of UPEC strain CFT073 to the presence of 0.3 M NaCl or 0.6 M urea in the growth medium. The cell responses to these two osmolytes were drastically different. Although most of the genes of the osmotically inducible regulon were overexpressed in medium with salt, urea failed to stimulate osmotic stress response. At the same time, UPEC colonization genes encoding type 1 and F1C fimbriae and capsule biosynthesis were transcriptionally induced in the presence of urea but did not respond to increased salt concentration. We speculate that urea can potentially be sensed by uropathogenic bacteria to initiate infection program. In addition, several molecular chaperone genes were overexpressed in the presence of urea, whereas adding NaCl to the medium led to an upregulation of a number of anaerobic metabolism pathways. PMID:23090957

Withman, Benjamin; Gunasekera, Thusitha S; Beesetty, Pavani; Agans, Richard; Paliy, Oleg

2013-01-01

57

Mild Combustion  

Microsoft Academic Search

The Mild Combustion is characterized by both an elevated temperature of reactants and low temperature increase in the combustion process. These features are the results of several technological demands coming from different application fields. This review paper aims to collect information which could be useful in understanding the fundamentals and applications of Mild Combustion. The information in this field are

Antonio Cavaliere; Mara de Joannon

2004-01-01

58

Continuous monitoring of urea levels during hemodialysis.  

PubMed

An ammonium ion-specific electrode system is evaluated for analysis of blood urea nitrogen from serum, plasma ultrafiltrate, or hemodialyzer dialysate fluid. The electrode shows a high sensitivity over clinically useful concentration ranges. Free serum ammonia, volatile amines, or urea ammonia after hydrolysis can be measured. In a double blind study excellent correlation was found for 187 blood urea nitrogen samples measured with the electrode with standard auto-analyzer techniques. Continuous monitoring of urea in dialysate fluid is described. Urea clearances were measured from dialysate effluent from an in vitro dialysis using conventional equipment. These values show excellent correlation to those from stnadard analysis methods. A continuous urea sensor for on-line hemodialysis application which can provide quantification of therapy is described. PMID:357303

Klein, E; Montalvo, J G; Wawro, R; Holland, F F; Lebeouf, A

1978-05-01

59

Chemical Structure and Curing Behavior of Phenol–Urea–Formaldehyde Cocondensed Resins of High Urea Content  

Microsoft Academic Search

Phenol–urea–formaldehyde cocondensed (PUF) resins of high urea content were prepared by adding different forms of urea to the reaction system. The structure, curing behavior, and water resistance of the PUF resins were investigated, and their relations were also discussed by liquid C nuclear magnetic resonance (NMR) and different scanning calorimetry (DSC). The liquid C-NMR analysis showed that urea added in

Dongbin Fan; Jianzhang Li; Jianmin Chang; Jinsheng Gou; Jinxue Jiang

2009-01-01

60

Spectroscopic characterization of urea aqueous solutions: experimental phase diagram of the urea-water binary system.  

PubMed

Raman spectroscopy was used to analyze mixtures of urea and water in order to identify the influence of the urea concentration on the solution's freezing point. Our approach consisted in the analysis of urea aqueous solutions and the determination of their phase transitions at low temperatures. Hence, Raman spectra of these solutions were acquired in a -30 to 10 °C temperature range. This enabled us to build the experimental phase diagram of the urea-water binary system. PMID:24067578

Durickovic, Ivana; Thiébaud, Laura; Bourson, Patrice; Kauffmann, Thomas; Marchetti, Mario

2013-10-01

61

Nitrogen and urea metabolism during continuous ambulatory peritoneal dialysis  

Microsoft Academic Search

Nitrogen and urea metabolism during continuous ambulatory peritoneal dialysis. During continuous ambulatory peritoneal dialysis (CAPD), concentrations of serum urea nitrogen (SUN) have been reported that are lower than what would be predicted from estimated dietary protein intake and the calculated urea clearance by dialysis. Net urea generation (urea nitrogen appearance) and losses of various nitrogenous constituents were measured during 12

Michael J Blumenkrantz; Joel D Kopple; John K Moran; Gerald P Grodstein; Jack W Coburn

1981-01-01

62

Calcium magnesium acetate and urea advanced reburning for NO control with simultaneous SO 2 reduction  

Microsoft Academic Search

Calcium magnesium acetate (CMA) shows potential as a reductant for simultaneous NOx and SOx removal from coal-fired combustion plant. The performance of urea co-injection with CMA on NO reduction in an ‘advanced reburn’ (AR) configuration has been investigated with a view to optimization of the process in a pulverized coal-fired furnace operating at 80kW. The impact on SO2 reduction has

W Nimmo; A. A Patsias; E Hampartsoumian; B. M Gibbs; M Fairweather; P. T Williams

2004-01-01

63

Effect of oxygenated liquid additives on the urea based SNCR process  

Microsoft Academic Search

An experimental investigation was performed to study the effect of oxygenated liquid additives, H2O2, C2H5OH, C2H4(OH)2 and C3H5(OH)3 on NOx removal from flue gases by the selective non-catalytic reduction (SNCR) process using urea as a reducing agent. Experiments were performed with a 150kW pilot scale reactor in which a simulated flue gas was generated by the combustion of methane operating

M. Tayyeb Javed; W. Nimmo; Asif Mahmood; Naseem Irfan

2009-01-01

64

Combustion synthesis of lanthanum chromite starting from water solutions: Investigation of process mechanism by DTA–TGA–MS  

Microsoft Academic Search

The mechanism of combustion synthesis of lanthanum chromite was investigated by carrying out simultaneous differential thermal analysis (DTA), thermal-gravimetric analysis (TGA) and quadrupole mass spectrometry measurements (MS). The whole process was found to involve several phenomena: urea and nitrates thermal decomposition, exothermal reactions occurring directly between nitrates and urea as well as between their decomposition products, final reaction between solid

S. Biamino; C. Badini

2004-01-01

65

The formation of poly(ester–urea) networks in the absence of isocyanate monomers  

Microsoft Academic Search

The polymerization of N,N? carbonylbis (caprolactam) (CBC) and polyol in the presence of alcoholate as catalyst produced cross-linked poly(ester–urea)s via ring opening addition reaction. In contrast to conventional synthetic routes, the use of non-toxic CBC eliminates the need for toxic isocyanate-based monomers. The structure of the molecules resulting from model reactions was confirmed using FT-IR and 1H- and 13C-NMR spectroscopy.

Jörg Zimmermann; Ton Loontjens; B. J. R. Scholtens; Rolf Mülhaupt

2004-01-01

66

Simple Ant Routing Algorithm  

Microsoft Academic Search

A mobile ad-hoc network has limited and scarce resources and thus routing protocols in such environments must be kept as simple as possible. This paper presents a MANET routing protocol, inspired in insect societies' biological models, the simple ant routing algorithm (SARA), which provides a simple and efficient routing solution. SARA uses a controlled neighbour broadcast route discovery procedure, aimed

Fernando Correia; T. Vazao

2008-01-01

67

Urea Kinetics and When to Commence Dialysis  

Microsoft Academic Search

Blood urea and serum creatinine levels are important factors in deciding when to start dialysis. Recently, in the assessment of dialysis adequacy, emphasis has shifted from reliance on these parameters to use of kinetic methods. We therefore applied urea kinetic modelling (UKM) to 63 consecutive chronic renal failure (CRF) patients at the time dialysis commenced and compared the results to

James Tattersall; Roger Greenwood; Ken Farrington

1995-01-01

68

Urea Transporter Physiology Studied in Knockout Mice  

PubMed Central

In mammals, there are two types of urea transporters; urea transporter (UT)-A and UT-B. The UT-A transporters are mainly expressed in kidney epithelial cells while UT-B demonstrates a broader distribution in kidney, heart, brain, testis, urinary tract, and other tissues. Over the past few years, multiple urea transporter knockout mouse models have been generated enabling us to explore the physiological roles of the different urea transporters. In the kidney, deletion of UT-A1/UT-A3 results in polyuria and a severe urine concentrating defect, indicating that intrarenal recycling of urea plays a crucial role in the overall capacity to concentrate urine. Since UT-B has a wide tissue distribution, multiple phenotypic abnormalities have been found in UT-B null mice, such as defective urine concentration, exacerbated heart blockage with aging, depression-like behavior, and earlier male sexual maturation. This review summarizes the new insights of urea transporter functions in different organs, gleaned from studies of urea transporter knockout mice, and explores some of the potential pharmacological prospects of urea transporters.

Li, Xuechen; Chen, Guangping; Yang, Baoxue

2012-01-01

69

Extraction of urea and ammonium ion  

NASA Technical Reports Server (NTRS)

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.

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

1977-01-01

70

40 CFR 721.9925 - Aminoethylethylene urea methacrylamide.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 false Aminoethylethylene urea methacrylamide. 721.9925 Section...Substances § 721.9925 Aminoethylethylene urea methacrylamide. (a) Chemical substance...identified generically as an aminoethylethylene urea methacrylamide (PMN...

2013-07-01

71

Computational combustion  

Microsoft Academic Search

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

Charles K. Westbrook; Yasuhiro Mizobuchi; Thierry J. Poinsot; Phillip J. Smith; Jürgen Warnatz

2005-01-01

72

Computational Combustion  

Microsoft Academic Search

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

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

2004-01-01

73

Urea transport through composite polyallylamine membranes  

NASA Technical Reports Server (NTRS)

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.

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

1977-01-01

74

Method for reducing nitrogen oxides in combustion effluents  

DOEpatents

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.

Zauderer, Bert (Merion Station, PA) [Merion Station, PA

2000-01-01

75

Ammonia sanitisation of sewage sludge using urea.  

PubMed

The aim of the study was to develop a simple, low-cost treatment for sewage sludge using urea as a sanitising agent. Sewage sludge was spiked with Enterococcus faecalis and Salmonella typhimurium, treated with 0.5, 1, 1.5 and 2% w/w urea at laboratory scale, and the viability was monitored during 4 months of storage at 4, 10 and 22 °C (only 0.5%). A linear relationship was identified between Salmonella spp. inactivation rate and ammonia (NH3) concentration. Temperature had a positive impact on Salmonella spp. inactivation at higher temperatures, but in the range 4-10 °C temperature influenced this inactivation merely by its impact on the ammonia equilibrium. Enterococcus spp. was more persistent and a lag phase of up to 11 weeks was observed. Higher temperature and ammonia concentration reduced the lag phase duration significantly, and also had a clear effect on the inactivation rate for the treatments with 0.5% urea at 22 °C and 2% urea at 4 and 10 °C. Urea sanitisation of sewage sludge can give a 2 log10 reduction of Enterococcus spp. and more than a 5 log10 reduction of Salmonella spp. within 6 weeks with either 0.5% w/w urea at 22 °C or 2% urea at 10 °C. PMID:24185072

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

2013-01-01

76

Inexpensive purification of urea waste streams  

US Patent & Trademark Office Database

Urea is destroyed in aqueous waste streams containing various anions and cations plus urea by contacting the stream with a cation exchange resin, then reacting the resulting stream with nitric oxide, nitrous acid or a nitrite salt to convert the urea to nitrogen, carbon dioxide and water and treating the resulting stream with an anion exchange resin. A pure aqueous stream is obtained which does not adversely affect the environment and which may be recycled to a plant as fresh water resulting in large monetary savings in fresh water cost.

1980-02-12

77

Gasification of wood to produce urea  

SciTech Connect

A study is described which examines the economic feasibility of producing urea by the gasification of wood. The process includes an oxygen blown fluidized bed gasifier, an air separation plant supplying both oxygen and nitrogen to the process, the use of a water gas process for hydrogen production, an Amine Guard AG/T carbon dioxide removal system, and a pressure swing absorption system for purifying the hydrogen used in the ammonia synthesis. Ammonia combined with carbon dioxide produces ammonium carbamate which is dehydrated to urea. The economic analysis shows that urea can be produced from wood at a profit. 5 references, 5 figures, 4 tables.

Bettinger, J.A.; Kosstrin, H.M.

1984-06-01

78

Combustion detector  

NASA Technical Reports Server (NTRS)

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.

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

1973-01-01

79

Combustion Physics.  

ERIC Educational Resources Information Center

Discusses how physics is used to improve the efficiency of combustion, pointing out that the interdisciplinary topic has applications to problems of real industrial relevance and practical value. (JN)

Jones, A. R.

1985-01-01

80

Predict Personal Continuous Route  

Microsoft Academic Search

In the daily life, people often repeat regular routes in certain periods. Predicting personal future routes using this information helps to achieve many goals, including improving the quality of intelligent transportation systems (ITSs) and location-based services (LBSs) for individuals. In this paper, a novel system is developed to predict the personal future routes based on the continuous route patterns extracted

Qian Ye; Ling Chen; Gencai Chen

2008-01-01

81

Compact routing schemes  

Microsoft Academic Search

We describe several compact routing schemes for general weighted undirected networks. Our schemes are simple and easy to implement. The routing tables stored at the nodes of the network are all very small. The headers attached to the routed messages, including the name of the destination, are extremely short. The routing decision at each node takes constant time. Yet, the

Mikkel Thorup; Uri Zwick

2001-01-01

82

Coulometric titration of urea with electrogenerated hypobromite.  

PubMed

A definitive method is described for the indirect assay of several tens of milligrams of urea by coulometric titration. Urea was decomposed in concentrated sulfuric acid using a Kjeldahl flask. Subsequently, the formed ammonium ion was titrated with electrogenerated hypobromite ion in a sodium bromide-sodium tetraborate medium of pH 8.6, with amperometric end-point detection. Parameters affecting the pretreatment procedure were evaluated. The optimized conditions included the heating of 2 g of urea at around 300°C for 2 h with 10 cm(3) of sulfuric acid. Under the proposed conditions, the assay value with expanded uncertainty (k = 2), 99.870 ± 0.026%, agreed well with the certified value of NIST SRM 912a urea, 99.9 ± 0.1%. PMID:23842420

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

2013-01-01

83

Detection of Interstellar Urea with Carma  

NASA Astrophysics Data System (ADS)

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 [(NH_2)_2CO] is a compact hot core molecule such as other large molecules, e.g. methyl formate and acetic acid (2009, 64th OSU Symposium On Molecular Spectroscopy, WI05). We have conducted an extensive search for urea toward the high mass hot molecular core Sgr B2(N-LMH) using 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, a major problem in identifying urea lines is confusion with lines of other molecules. Therefore, 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. The 2.5^"×2^" synthesized beam of CARMA 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 T-test to the high resolution channel maps obtained from CARMA. The T-test shows similar 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 to systematically determine the credibility of detections of weaker signals from new and larger interstellar molecules.

Kuo, H.-L.; Snyder, L. E.; Friedel, D. N.; Looney, L. W.; McCall, B. J.; Remijan, A. J.; Lovas, F. J.; Hollis, J. M.

2010-06-01

84

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

Microsoft Academic Search

New NixMg1?xAl2O4 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 (MgAl2O4) was used as crystalline host network for the synthesis of nickel-based nano ceramic pigments.

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

2011-01-01

85

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

PubMed Central

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

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

1994-01-01

86

Evacuation Route Planning Algorithm: Longer Route Preferential  

Microsoft Academic Search

Given a transportation network with capacity constraints, the initial occupancies and the destination nodes, evacuation route\\u000a planning generates a set of evacuation routes and a schedule for the movement of people and vehicles along these routes, such\\u000a that the evacuation is completed in the shortest possible time. This is a critical step in disaster emergency management and\\u000a homeland defense preparation.

Maimai Zeng; Cheng Wang

2009-01-01

87

Bubble Combustion  

NASA Technical Reports Server (NTRS)

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, a computational model developed at Glenn, that simulates the cavitational collapse of a single bubble in a liquid (water) and the subsequent combustion of the gaseous contents inside the bubble. The model solves the time-dependent, compressible Navier-Stokes equations in one-dimension with finite-rate chemical kinetics using the CHEMKIN package. Specifically, parameters such as frequency, pressure, bubble radius, and the equivalence ratio were varied while examining their effect on the maximum temperature, radius, and chemical species. These studies indicate that the radius of the bubble is perhaps the most critical parameter governing bubble combustion dynamics and its efficiency. Based on the results of the parametric studies, we plan on conducting experiments to study the effect of ultrasonic perturbations on the bubble generation process with respect to the bubble radius and size distribution.

Corrigan, Jackie

2004-01-01

88

Biofuels combustion.  

PubMed

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. PMID:23298249

Westbrook, Charles K

2013-01-01

89

Compliant Walled Combustion Devices.  

National Technical Information Service (NTIS)

Combustion devices described herein comprise a compliant combustion chamber wall or segment. The compliant segment deforms during combustion in the combustion chamber. Some devices may include a compliant wall configured to stretch responsive to pressure ...

H. Prahlad J. Helm R. E. Pelrine S. Oh S. E. Stanford

2005-01-01

90

Evaluation of urea reduction ratio estimated from the integrated value of urea concentrations in spent dialysate.  

PubMed

We propose a new apparatus and method to estimate accurate urea reduction ratio without influence of any rebound. For this purpose, we have developed an improved version of a chemiluminescence-based urea sensor capable of measuring urea concentration in spent dialysate (CD ) at 2-min intervals. The correlation coefficient between the readouts of the sensor and the conventional enzyme-UV method was 0.97 and the sensor was not affected by 9?mmol/L uric acid, creatinine, or ammonia. Using the urea sensor, CD was measured as a function of dialysis time t during dialysis sessions for various blood flow rates. The urea reduction ratio based on the mass of the urea reduced (m URR) was estimated from the integrated value of CD (t). When in vitro urea concentrations are measured during a dialysis session in model blood (urea solution) at a constant volume (V) in a vessel, the plots of m URR were congruous with theoretical curves of conventional URR calculated based on the one-pool model, and thus the accuracy of m URR was confirmed. On the other hand, in in vivo measurements of CD (t) during dialysis treatment for two patients, the plots of the m URR were not congruous with the theoretical curves of URR. Such a difference between URR and m URR was explained by the deviation of actual dialysis from the one-pool model, and it was concluded that m URR might be accurate under any dialysis condition. PMID:24720411

Ozaki, Masahiro; Hori, Jun'ya; Okabayashi, Tohru

2014-04-01

91

Urea handling by the medullary collecting duct of the rat kidney during hydropenia and urea infusion  

Microsoft Academic Search

Previous micropuncture studies of distal tubule fluid and ureteral urine have indicated a varying degree of urea reabsorption in the collecting duct. In the present experiments the microcatheterization technique was used to directly determine urea, Na, K, total solute and fluid reabsorption along the length of the medullary collecting duct in anaesthetized hydropenic rats and in rats given low dose

H. Sonnenberg; D. R. Wilson

1981-01-01

92

Urea release rate from a scoop of coated pure urea beads: Unified extreme analysis  

Microsoft Academic Search

Urea release from a scoop of coated beads in a given volume of a well stirred liquid has been investigated analytically and experimentally. A method for determining the fractional cumulative release and fractional release rate curves for the scoop without knowing particle number and radii is presented. The representative D\\/Kb for a scoop of urea beads spray coated with ethyl

S. M. Lu; Szu-Lin Chang; Wen-Yu Ku; Hou-Chien Chang; Jiunn-Yau Wang; Duu-Jong Lee

2007-01-01

93

Combustion synthesis, characterization and sintering behavior of magnesium aluminate (MgAl 2O 4) powders  

Microsoft Academic Search

Nanocrystalline magnesium aluminate powders with different specific surface area, morphology and crystallite size were obtained by combustion synthesis using triethylenetetramine and a mixture of urea and triethylenetetramine, respectively. Triethylenetetramine yields after annealing at 700°C a spinel powder with a BET surface area of 175.8m2g?1 and an average crystallite size of 4.9nm. Urea and triethylenetetramine fuel mixture lead after annealing at

Robert Iano?; Radu Laz?u

2009-01-01

94

Catalytic routes to transportation fuels utilizing natural gas hydrates  

Microsoft Academic Search

Gas hydrates hold >50% of earth's total combustible carbon. To make this vast but dilute (CH4?3.9wt%) energy source available, an economical three-step route is outlined. A major technological challenge is environmentally-benign mining of gas hydrates that releases “Aqueous CH4” and makes it available at the surface (Step 1). Step 2 involves a cost-effective partial oxidation (POX) with air route that

James E. Wegrzyn; Devinder Mahajan; Michael Gurevich

1999-01-01

95

Experimental and modeling study of the effect of CO and H 2 on the urea DeNO x process in a 150 kW laboratory reactor  

Microsoft Academic Search

An experimental and modeling investigation has been performed to study the effect of process additives, H2 and CO on NOx removal from flue gases by a selective non-catalytic reduction process using urea as a reducing agent. Experiments were performed with a flow reactor in which flue gas was generated by the combustion of propane in air at 3% excess oxygen

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

2008-01-01

96

Pure and doped lanthanum cobaltites obtained by combustion method  

Microsoft Academic Search

We report the synthesis of La1?xSrxCoO3 nanopowders by solution combustion method using metal nitrates and ?-alanine (alanine method) or urea (urea method) as fuel. The influence of metal nitrates\\/organic substance molar ratio and the type of fuel was investigated. The isolated complex precursors were characterized by atomic absorption spectroscopy (AAS), FT-IR spectra and DTA–TG analysis. The La1?xSrxCoO3 (x=0–0.3) powders were characterized

D. Berger; C. Matei; F. Papa; G. Voicu; V. Fruth

2007-01-01

97

Go the Yeshiva Route?  

ERIC Educational Resources Information Center

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

Miles, Leland

1981-01-01

98

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

PubMed Central

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.

Liew, Hon Jung; De Boeck, Gudrun; Walsh, Patrick J.

2013-01-01

99

Noninjection routes for immunotherapy  

Microsoft Academic Search

Allergen specific immunotherapy, together with drugs and allergen avoidance, is a cornerstone in the management of respiratory allergy. The traditional subcutaneous route is burdened with the risk of severe adverse events; therefore, safer routes of administration (noninjection or local routes) have been investigated and developed. Controlled trials failed to demonstrate the clinical efficacy and the safety of oral and bronchial

Giorgio Walter Canonica; Giovanni Passalacqua

2003-01-01

100

Proxies For Anonymous Routing  

Microsoft Academic Search

Using traffic analysis, it is possible to infer who is talking to whom over a public network. This paper describes a flexible communications infrastructure, onion routing, which is resistant to traffic analysis. Onion routing lives just beneath the application layer, and is designed to interface with a wide variety of unmodified Internet services by means of proxies. Onion routing has

Michael G. Reed; Paul F. Syverson; David M. Goldschlag

1996-01-01

101

Small-Scale Application of Urea Based Selective Non-Catalytic Reduction of Nitric Oxide in Diesel Burning Effluent  

Microsoft Academic Search

Selective Non-Catalytic Reduction (SNCR) of nitric oxide has been studied experimentally injecting different concentrations of aqueous urea solution in a pilot-scale diesel fired tunnel furnace, which was set to run at 3-4% excess oxygen level and was producing low ppm of baseline NOx ranged from 65 to 74 ppm within the investigated temperature range. The furnace simulated small-scale combustion systems

Khandoker Abul Hossain; Mohammad Nazri; Farid Nasir Ani; Azeman Mustafa

102

Uric acid and urea in human sweat.  

PubMed

The present study investigated whether thermal sweating may relieve elevated concentrations of serum uric acid or urea. Concentrations of uric acid and urea were measured in the sweat of sixteen male volunteers, who were treated with external heat after one hour of intense physical exercise. The same analytes were also measured in their urine and serum samples. Furthermore, creatinine and some electrolytes were determined in these specimens. The results show that the concentration of uric acid in the sweat is 24.5 micromol/L, which is only 6.3% of that in serum. The concentration of urea in the sweat is 22.2 mmol/L, which is 3.6 times that in serum. The results indicate that sweat uric acid concentration is quite minimal, and the estimated total uric acid excretion per day in normal physiological range is insignificant. However, the level of sweat urea was found at a much higher concentration than the serum level. No correlation could be established between the level of uric acid in sweat and in serum. There was also no correlation between the level of urea in sweat and that in serum. These results suggest it would not be effective to relieve the elevated serum uric acid concentration by thermal sweating when the renal excretion of uric acid is partly compromised. Nevertheless, the potential of urea excretion via profuse sweating is apparent particularly when the kidneys are damaged or their function is impaired. These findings also suggest that persons who take vigorous exercise or are exposed to hot environments should be well advised to drink adequate fluids since heavy sweating excretes only minimal uric acid, accompanied by significant diminution of urinary output and diminished urinary excretions of uric acid, which may induce elevated levels of serum uric acid. PMID:12817713

Huang, Chien-Tsai; Chen, Mei-Lien; Huang, Li-Ling; Mao, I-Fang

2002-09-30

103

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

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

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

2011-10-15

104

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)

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.

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

2011-10-01

105

Wood plastic composite at different urea concentrations  

NASA Astrophysics Data System (ADS)

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

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

1995-04-01

106

1-(o-Tol-yl)thio-urea  

PubMed Central

In the title compound, C8H10N2S, the o-tolyl group and the thio­urea core are planar. The mean planes of the two groups are almost perpendicular [82.19?(8)°]. The thio­urea group is in the thio­amide form, in which resonance is present. In the crystal structure, mol­ecules are linked by inter­molecular N—H?S hydrogen bonds, forming two infinite chains parallel to the (110) and (10) planes.

Correa, Rodrigo S.; Ribeiro, Leandro; Ellena, Javier; Estevez-Hernandez, Osvaldo; Duque, Julio

2008-01-01

107

Role of thin descending limb urea transport in renal urea handling and the urine concentrating mechanism  

PubMed Central

Urea transporters UT-A2 and UT-B are expressed in epithelia of thin descending limb of Henle's loop and in descending vasa recta, respectively. To study their role and possible interaction in the context of the urine concentration mechanism, a UT-A2 and UT-B double knockout (UT-A2/B knockout) mouse model was generated by targeted deletion of the UT-A2 promoter in embryonic stem cells with UT-B gene knockout. The UT-A2/B knockout mice lacked detectable UT-A2 and UT-B transcripts and proteins and showed normal survival and growth. Daily urine output was significantly higher in UT-A2/B knockout mice than that in wild-type mice and lower than that in UT-B knockout mice. Urine osmolality in UT-A2/B knockout mice was intermediate between that in UT-B knockout and wild-type mice. The changes in urine osmolality and flow rate, plasma and urine urea concentration, as well as non-urea solute concentration after an acute urea load or chronic changes in protein intake suggested that UT-A2 plays a role in the progressive accumulation of urea in the inner medulla. These results suggest that in wild-type mice UT-A2 facilitates urea absorption by urea efflux from the thin descending limb of short loops of Henle. Moreover, UT-A2 deletion in UT-B knockout mice partially remedies the urine concentrating defect caused by UT-B deletion, by reducing urea loss from the descending limbs to the peripheral circulation; instead, urea is returned to the inner medulla through the loops of Henle and the collecting ducts.

Lei, Tianluo; Zhou, Lei; Layton, Anita T.; Zhou, Hong; Zhao, Xuejian; Bankir, Lise

2011-01-01

108

State alternative route designations  

SciTech Connect

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.

Not Available

1989-07-01

109

Defining Dynamic Route Structure  

NASA Technical Reports Server (NTRS)

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.

Zelinski, Shannon; Jastrzebski, Michael

2011-01-01

110

Effect of urea concentration on aggregation of amyloidogenic hexapeptides (NFGAIL).  

PubMed

We have performed large-scale all-atom molecular dynamics (MD) simulations to study the aggregation behavior of four NFGAIL hexapeptides in the aqueous urea solution, with a urea concentration ranging from 0 to 5 M. We find that urea in general suppresses the peptide aggregation, but suppression slows down in the intermediation concentration regime around 3 M. Two competing mechanisms of urea are determined: urea molecules accumulated near the first solvation shell (FSS) tend to unfold the hexapeptide, which favors aggregation; on the other hand, the tight hydrogen bonds formed between urea and peptide mainchains hinder the association of peptides which disfavors the formation of the ?-sheet. Furthermore, the different nonlinear urea concentration dependences of the urea-peptide and peptide-peptide hydrogen bonds lead to a nonmonotonic behavior, with a weak enhancement in the peptide aggregation around 3 M. PMID:24328094

Cai, Zhuowei; Li, Jingqiang; Yin, Chunji; Yang, Zaixing; Wu, Jianlan; Zhou, Ruhong

2014-01-01

111

Fault Detection in Routing Protocols  

Microsoft Academic Search

Routing protocol faults cause problems ranging from an inability to communicate to excessive routing overhead. This paper proposes a system for detecting a wide range of routing protocol faults. Our system deploys virtual routers called RouteMonitors to monitor a routing protocol. We de- ployed RouteMonitors in the MBone's DVMRP infrastruc- ture and uncovered a number of faults. We were also

Daniel Massey; Bill Fenner

1999-01-01

112

Aldehyde-containing urea-absorbing polysaccharides  

NASA Technical Reports Server (NTRS)

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.

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

1977-01-01

113

Wood plastic composite at different urea concentrations  

Microsoft Academic Search

Wood plastic composite (WPC) has been prepared with a low grade wood simul (Salmalia malabarica) of Bangladesh under Co-60 gamma irradiation using MMA as the bulk monomer combined with methanol as the swelling solvent at different urea concentrations. Effect of a second solute such as NVP, TPGDA and TMPTA in the impregnating solution is evaluated. NVP appears to be the

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

1995-01-01

114

Synergetic effects of nanoporous support and urea on enzyme activity.  

PubMed

We report synergetic effects of functionalized mesoporous silica (FMS) and urea to promote favorable protein conformational changes. The specific activity of glucose isomerase (GI) entrapped in FMS in the presence of urea was approximately double that of GI in solution in the absence of urea. Rather than losing all activity in a denaturing solution of 8.0 M urea, the specific activity of GI entrapped in FMS remained higher than the highest specific activity of GI free in solution. PMID:17341123

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

2007-04-01

115

Molecular recognition: A simple dinaphthyridine receptor for urea  

Microsoft Academic Search

A new dinaphthyridine receptor 1 is designed that efficiently binds to urea probably by six hydrogen bonds forming a chloroform soluble 1:1 complex and selectively extracts urea into chloroform from its mixture with thiourea. The receptor 1 has fifteen fold higher binding constant for urea than the truncated receptor 2 possibly due to formation of greater number of hydrogen bonds

Shyamaprosad Goswami; Rakhi Mukherjee

1997-01-01

116

Tracer Studies of Urea Kinetics in Growing Pigs: I. The Effect of Intravenous Infusion of Urea on Urea Recycling and the Site of Urea Secretion into the Gastrointestinal Tract  

Microsoft Academic Search

Four gilts (average BW 80 kg) were used in the first experiment to study the effect of i.v. infusion of urea on urea kinetics by means of a radioisotope dilution technique. The pigs were fed twice daily 600 g of a cornstarch-based diet formulated to contain 16% CP by supplementation with isolated soy protein. Infusion of urea, com- pared with

W. C. Sauers R. Mosenthinz; C. F. M. de Lange

2010-01-01

117

75 FR 74746 - Solid Urea From Russia and Ukraine  

Federal Register 2010, 2011, 2012, 2013

...731-TA-340-E and 340-H (Third Review)] Solid Urea From Russia and Ukraine AGENCY: United...concerning the antidumping duty orders on solid urea from Russia and Ukraine...of the antidumping duty orders on solid urea from Russia and Ukraine would be...

2010-12-01

118

76 FR 15339 - Solid Urea From Russia and Ukraine  

Federal Register 2010, 2011, 2012, 2013

...731-TA-340-E and 340-H (Third Review)] Solid Urea From Russia and Ukraine AGENCY: United...concerning the antidumping duty orders on solid urea from Russia and Ukraine...of the antidumping duty orders on solid urea from Russia and Ukraine would be...

2011-03-21

119

76 FR 77015 - Solid Urea From Russia and Ukraine  

Federal Register 2010, 2011, 2012, 2013

...340-E and 340-H (Third Review)] Solid Urea From Russia and Ukraine Determination On...of the antidumping duty orders on solid urea from Russia and Ukraine would be likely...4279 (December 2011), entitled Solid Urea from Russia and Ukraine:...

2011-12-09

120

Synergetic Effects of Nanoporous Support and Urea on Enzyme Activity  

SciTech Connect

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.

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

2007-02-01

121

21 CFR 176.320 - Sodium nitrate-urea complex.  

Code of Federal Regulations, 2013 CFR

...2013-04-01 2013-04-01 false Sodium nitrate-urea complex. 176.320 Section 176.320 Food...and Paperboard § 176.320 Sodium nitrate-urea complex. Sodium nitrate-urea complex may be safely used as a component...

2013-04-01

122

Incorporation of nitrification inhibitors with urea and urea-ammonium nitrate for irrigated corn  

Microsoft Academic Search

Nitrapyrin [2-chloro-6-(trichloromethyl)pyridine] has been shown to delay nitrification and may increase nitrogen (N) utilization efficiency of crops under N loss conditions. Current application recommendations suggest immediate incorporation. With fertilizer N sources such as urea and urea-ammonium nitrate (UAN) solution, immediate incorporation may not be practical. Experiments were conducted with irrigated corn (Zea mays L.) over 3 years to determine if

G. L. Malzer

1988-01-01

123

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

Microsoft Academic Search

Slow release 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 aqueous urea ammonium nitrate (UAN) ((NH2)2CO, NH4NO3) during a 2-yr field experiment in North Carolina. Crops were grown on Candor (sandy, siliceous, thermic Grossarenic Kandiudults),

Sheri Cahill; Deanna Osmond; Carl Crozier; Daniel Israel; Randy Weisz

2007-01-01

124

Choice of urea-spray models in CFD simulations of urea-SCR systems  

Microsoft Academic Search

The sensitivity of modeling choices to obtained results for Eulerian–Lagrangian CFD simulations of urea-SCR systems has been investigated for a system consisting of an AdBlue-spray located at the exhaust pipe wall, directed into the exhaust gas flow. The decomposition of urea is modeled as being heat transfer limited and taking place at a constant temperature (425K). It is shown that

Henrik Ström; Andreas Lundström; Bengt Andersson

2009-01-01

125

Protecting group free synthesis of urea-linked glycoconjugates: efficient synthesis of ?-urea glycosides in aqueous solution.  

PubMed

A method for the protecting group free synthesis of ?-urea-linked glycoconjugates has been developed. The one step process, involving reactions between urea and d-glucose, N-acetyl-d-glucosamine or d-xylose in acidic aqueous solution, furnishes the corresponding ?-urea glycosides in modest yields. This simple and efficient procedure is applicable to the synthesis of ?-urea tethered amino acid-carbohydrate conjugates. PMID:24796538

Ichikawa, Yoshiyasu; Minami, Takahiro; Kusaba, Shohei; Saeki, Nobuyoshi; Tonegawa, Yuta; Tomita, Yumiko; Nakano, Keiji; Kotsuki, Hiyoshizo; Masuda, Toshiya

2014-05-21

126

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

127

FIELD AND LABORATORY STUDIES COMPARING NUTRISPHERE-NITROGEN UREA WITH UREA IN NORTH DAKOTA, ARKANSAS, AND MISSISSIPPI  

Microsoft Academic Search

Nitrification and ammonia volatility are two important impediments to nitrogen (N) use efficiency and crop uptake around the world. Nutrisphere® is a relatively new product whose manufacturer claims both nitrification and urea volatilization inhibiting properties. Urea coated with Nutrisphere is and the resulting fertilizer is called Nutrisphere®-N urea, or Nutrisphere-N (NSN). Eight field studies on spring (Triticum aestivum L.) or

David Franzen; R. Jay Goos; Richard J. Norman; Timothy W. Walker; Trenton L. Roberts; Nathan A. Slaton; Gregory Endres; Roger Ashley; James Staricka; John Lukach

2011-01-01

128

Quality of Service Routing  

Microsoft Academic Search

Constraint-based routing is an invaluable part of a full-fledged Quality of Service architecture. Unfortunately, QoS routing with multi- ple additive constraints is known to be a NP-complete problem. Hence, accurate constraint-based routing algorithms with a fast running time are scarce, perhaps even non-existent. The need for such algorithms has resulted in the proposal of numerous heuristics and a few exact

Piet Van Mieghem; Fernando A. Kuipers; Turgay Korkmaz; Marwan Krunz; Marília Curado; Edmundo Monteiro; Xavier Masip-bruin; Josep Solé-pareta; Sergio Sánchez-lópez

2003-01-01

129

Combustibility of titanium powders  

NASA Technical Reports Server (NTRS)

The combustion of compact samples was studied; the mechanism of autoignition is defined. Several studies are made of the combustibility of titanium using 50 samples. The data provide a clear idea of the combustibility of titanium powders.

Popov, Ye. I.; Poyarkov, V. G.; Finayev, Yu. A.

1989-01-01

130

Coal Combustion and Utilization.  

National Technical Information Service (NTIS)

Information on the following subjects is included within the scope of the publication, but all subjects may not appear in each issue: coal combustion, power plant fuel, MHD generators, fuel cells, combustion chemistry, combustion systems.

1986-01-01

131

Contact Graph Routing  

NASA Technical Reports Server (NTRS)

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. The information carried by CGR contact plan messages is useful not only for dynamic route computation, but also for the implementation of rate control, congestion forecasting, transmission episode initiation and termination, timeout interval computation, and retransmission timer suspension and resumption.

Burleigh, Scott C.

2011-01-01

132

The study of combustion synthesis of fine-particle ?-lithium aluminate  

Microsoft Academic Search

Fine-particle ?-lithium aluminate has been prepared by the combustion of mixtures of the metal nitrates, M(NO3)x(M = Li, Al) as oxidizers and urea and citric acid as fuels, at low temperature and short reaction time. The combustion products were identified from X-ray powder diffraction (XRD) patterns, scanning electron microscopy (SEM), and pore size distribution measurements. As the total composition of

Wei Lin; Xinde Bai; Yunhan Ling; Jinlong Yang; Wenjun Ma

2003-01-01

133

Structural and electrochemical properties of LiCoO 2 prepared by combustion synthesis  

Microsoft Academic Search

LiCoO2 powders were prepared by combustion synthesis, using metallic nitrates as the oxidant and metal sources and urea as fuel. A small amount of the LiCoO2 phase was obtained directly from the combustion reaction, however, a heat treatment was necessary for the phase crystallization. The heat treatment was performed at the temperature range from 400 up to 700 °C for

E. I. Santiago; A. V. C. Andrade; C. O. Paiva-Santos; L. O. S. Bulhoes

2003-01-01

134

Inactivation of Maize Phosphoenolpyruvate Carboxylase by Urea 1  

PubMed Central

Phosphoenolpyruvate carboxylase purified from leaves of maize (Zea mays, L.) is sensitive to the presence of urea. Exposure to 2.5 m urea for 30 min completely inactivates the enzyme, whereas for a concentration of 1.5 m urea, about 1 h is required. Malate appears to have no effect on inactivation by urea of phosphoenolpyruvate carboxylase. However, the presence of 20 mm phosphoenolpyruvate or 20 mm glucose-6-phosphate prevents significant inactivation by 1.5 m urea for at least 1 h. The inactivation by urea is reversible by dilution. The inhibition by urea and the protective effects of phosphoenolpyruvate and glucose-6-phosphate are associated with changes in aggregation state.

Wedding, Randolph T.; Dole, Paul; Chardot, Thierry P.; Wu, Min-Xian

1992-01-01

135

Preparation of nanoparticle size LiBiO 2 by combustion method and its electrochemical studies for lithium secondary cells  

Microsoft Academic Search

A simple combustion method has been tried for the preparation of nanoparticle-sized LiBiO2 powder with urea as the igniter and glycerol as the binding material. Nitrates of Li+ and Bi3+ were mixed together to form a uniform mixture. Required quantities of urea and glycerol were added to this mixture to form\\u000a a paste. This paste was carefully heated to 100°

R. Sathiyamoorthi; A. Subramania; R. Gangadharan; T. Vasudevan

2005-01-01

136

1-Furfuryl-3-furoylthio-urea  

PubMed Central

The title compound, C11H10N2O3S, was synthesized from furoyl isothio­cyanate and furfurylamine in dry acetone. The thio­urea group is in the thio­amide form. The trans–cis geometry of the thio­urea group is stabilized by intra­molecular hydrogen bonding between the carbonyl and cis-thio­amide and results in a pseudo-S(6) planar ring which makes dihedral angles of 2.5?(3) and 88.1?(2)° with the furoyl and furfuryl groups, respectively. There is also an intra­molecular hydrogen bond between the furan O atom and the other thio­amide H atom. In the crystal structure, mol­ecules are linked by two inter­molecular N—H?O hydrogen bonds, forming dimers. These dimers are stacked within the crystal structure along the [010] direction.

Estevez-Hernandez, O.; Duque, J.; Ellena, J.; Correa, Rodrigo S.

2008-01-01

137

Ammonium and urea removal by Spirulina platensis  

Microsoft Academic Search

Different concentrations either of ammonium chloride or urea were used in batch and fed-batch cultivations of Spirulina platensis to evaluate the possibility of substituting nitrate by cheaper reduced nitrogen sources in wastewaters biotreatment. The\\u000a maximum nitrogen concentration able to sustain the batch growth of this microalga without inhibition was 1.7 mM in both cases.\\u000a Ammonium chloride was limiting for the growth

A. Converti; S. Scapazzoni; A. Lodi; J. C. M. Carvalho

2006-01-01

138

Thienopyridine urea inhibitors of KDR kinase  

Microsoft Academic Search

A series of substituted thienopyridine ureas was prepared and evaluated for enzymatic and cellular inhibition of KDR kinase activity. Several of these analogs, such as 2, are potent inhibitors of KDR (<10nM) in both enzymatic and cellular assays. Further characterization of inhibitor 2 indicated that this analog possessed excellent in vivo potency (ED50 2.1mg\\/kg) as measured in an estradiol-induced mouse

H. Robin Heyman; Robin R. Frey; Peter F. Bousquet; George A. Cunha; Maria D. Moskey; Asma A. Ahmed; Niru B. Soni; Patrick A. Marcotte; Lori J. Pease; Keith B. Glaser; Melinda Yates; Jennifer J. Bouska; Daniel H. Albert; Candace L. Black-Schaefer; Peter J. Dandliker; Kent D. Stewart; Paul Rafferty; Steven K. Davidsen; Michael R. Michaelides; Michael L. Curtin

2007-01-01

139

Intelligent MANET routing optimizer  

Microsoft Academic Search

In Mobile Ad Hoc Network (MANET) many routing protocols exist, which are capable of routing data packets from source to destination. Each protocol is designed to fulfill its requirement; the constant network context (i.e. number of nodes, mobility, etc); but network context could be changed during the running time which affects the protocol performance and reduces its efficiency. In this

N. H. Saeed; M. F. Abbod; H. S. Al-Raweshidy; O. Raoof

2008-01-01

140

Internet routing instability  

Microsoft Academic Search

This paper examines the network interdomain rout- ing information exchanged between backbone service providers at the major U.S. public Internet exchange points. Internet rout- ing instability, or the rapid fluctuation of network reachability information, is an important problem currently facing the In- ternet engineering community. High levels of network instability can lead to packet loss, increased network latency and time

Craig Labovitz; G. Robert Malan; Farnam Jahanian

1998-01-01

141

Cashmere: Resilient Anonymous Routing  

Microsoft Academic Search

Anonymous routing protects user communication from identification by third-party observers. Existing anony- mous routing layers utilize Chaum-Mixes for anonymity by relaying traffic through relay nodes called mixes. The source defines a static forwarding path through which traffic is relayed to the destination. The resulting path is fragile and shortlived: failure of one mix in the path breaks the forwarding path

Li Zhuang; Feng Zhou; Ben Y. Zhao; Antony I. T. Rowstron

2005-01-01

142

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...

143

Dichloridobis(thio-urea-?S)nickel(II)  

PubMed Central

The title complex, [NiCl2(CH4N2S)2], has been synthesized from the previously reported (diamino­methyl­idene)sulfonium chloride–thio­urea (3/2) salt [Zouihri (2012b ?). Acta Cryst. E68, o257]. The NiII ion is coordinated in a distorted tetra­hedral geometry by two mol­ecules of thio­urea [Ni—S = 2.3079?(7) and 2.3177?(6)?Å] and two chloride anions [Ni—Cl = 2.2516?(7) and 2.2726?(7)?Å]. The bond angles at the Ni atom lie between 96.69?(2) and 115.40?(3)°, while the dihedral angle between the mean planes of the two thio­urea ligands is 6.36?(15)°. The crystal structure is characterized by intra- and inter­molecular N—H?Cl hydrogen bonds, which lead to the formation of two-dimensional networks lying parallel to the ab plane. The networks are linked via classical N—H?Cl and N—H?S hydrogen bonds, forming a three-dimensional arrangement.

Zouihri, Hafid

2012-01-01

144

Dichloridobis(thio-urea-?S)nickel(II).  

PubMed

The title complex, [NiCl(2)(CH(4)N(2)S)(2)], has been synthesized from the previously reported (diamino-methyl-idene)sulfonium chloride-thio-urea (3/2) salt [Zouihri (2012b ?). Acta Cryst. E68, o257]. The Ni(II) ion is coordinated in a distorted tetra-hedral geometry by two mol-ecules of thio-urea [Ni-S = 2.3079?(7) and 2.3177?(6)?Å] and two chloride anions [Ni-Cl = 2.2516?(7) and 2.2726?(7)?Å]. The bond angles at the Ni atom lie between 96.69?(2) and 115.40?(3)°, while the dihedral angle between the mean planes of the two thio-urea ligands is 6.36?(15)°. The crystal structure is characterized by intra- and inter-molecular N-H?Cl hydrogen bonds, which lead to the formation of two-dimensional networks lying parallel to the ab plane. The networks are linked via classical N-H?Cl and N-H?S hydrogen bonds, forming a three-dimensional arrangement. PMID:22412454

Zouihri, Hafid

2012-03-01

145

Automatic routing module  

NASA Technical Reports Server (NTRS)

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.

Malin, Janice A.

1987-01-01

146

Route 66 University  

NSDL National Science Digital Library

Millions of people learned about Route 66 and how it wound from Chicago to L.A. courtesy of Nat Cole, others from its namesake 1960s television series, and now interested parties can learn online about that fabled stretch of road on this Route 66 University website. Neophytes may want to begin by perusing the section dedicated to maps of the route, allowing them to visualize how it winds through Illinois, Missouri, Kansas, and other states. The site's main page also contains sections that provide electronic postcards, an events calendar, and the "Campus Rag," which provides timely information about the history of this road. The essays and articles here are a true delight, as they range from reminiscences of Route 66 from novelist Michael Lund to a 1996 interview with Roy Rogers. Another section of the site that is worth taking a look at is called "I Rememberâ¦," and features first-hand memories of life along Route 66.

147

Long-Term Regulation of Renal Urea Transporters during Antidiuresis  

PubMed Central

To produce a concentrated urine, the renal medulla needs hypertonicity for the reabsorption of free water from collecting duct. The single effect that increases interstitial tonicity in the outer medulla is the active NaCl reabsorption in the thick ascending limb, while the single effect in the inner medulla is the passive efflux of NaCl through the thin ascending limb. The passive mechanism in the inner medulla requires high interstitial urea concentration. Two main groups of urea transporters (UT-A, UT-B) are present in the kidney, which maintains the high concentration of urea in the deepest portion of the inner medulla by intra-renal urea recycling. Recent studies suggest that UT-A1 in the terminal inner medullary collecting duct is up-regulated when urine or inner medullary interstitial urea is depleted in order to enhance the reabsorption of urea, while UT-A2 in the descending thin limb of loops of Henle and UT-B in the descending vasa recta are increased when outer medullary interstitial urea concentration is high, in order to prevent the loss of urea from the medulla to the systemic circulation, thereby increasing intra-renal urea recycling. This review will summarize the functions of the renal urea transporters in urine concentration mechanism and the recent knowledge about their long-term regulation.

2006-01-01

148

Routing Vehicles with Ants  

NASA Astrophysics Data System (ADS)

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.

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

149

Coal combustion science  

SciTech Connect

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.

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

1990-11-01

150

Use of Urea by Early Postpartum Holstein Cows  

Microsoft Academic Search

Thirty-nine lactating Holstein cows were fed high-energy complete rations ad libitum with crude protein: 1) 11.7% (negative control); 2) 13.9% (1% urea); 3) 16.6% (1% urea); or 4) 16.6% (positive control) in a continuous 12-wk study beginning at wk 5 postpartum. Milk production of 27.7, 31.8, 34.0, and 30.4 kg\\/day showed the use of urea nitrogen by groups 2 and

K. Kwan; C. E. Coppock; G. B. Lake; M. J. Fettman; L. E. Chase; R. E. McDowell

1977-01-01

151

The distribution of urea in coastal and oceanic waters  

Microsoft Academic Search

The distribution of urea has been determined for certain coastal and oceanic waters. The presence of urea-nitrogen in surface waters off the continental shelf between Panama and Callao, Peru, was extremely patchy and varied in concentration from 0.54-5.00 pg- atom urea-N\\/liter. The higher values were generally from samples collected within a foam slick or windrow. Surface waters in nonupwelling waters

CHARLES C. REMSON

1971-01-01

152

14C-urea breath test in C pylori gastritis  

Microsoft Academic Search

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

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

1989-01-01

153

Cloning and characterization of the vasopressin-regulated urea transporter  

Microsoft Academic Search

UREA is the principal end product of nitrogen metabolism in mammals1. Movement of urea across cell membranes was originally thought to occur by lipid-phase permeation, but recent studies have revealed the existence of specialized transporters with a low affinity for urea (Km > 200 mM)2. Here we report the isolation of a complementary DNA from rabbit renal medulla that encodes

Guofeng You; Craig P. Smith; Yoshikatsu Kanai; Wen-Sen Lee; Matthias Stelzner; Matthias A. Hediger

1993-01-01

154

Class network routing  

DOEpatents

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.

Bhanot, Gyan (Princeton, NJ) [Princeton, NJ; Blumrich, Matthias A. (Ridgefield, CT) [Ridgefield, CT; Chen, Dong (Croton On Hudson, NY) [Croton On Hudson, NY; Coteus, Paul W. (Yorktown Heights, NY) [Yorktown Heights, NY; Gara, Alan G. (Mount Kisco, NY) [Mount Kisco, NY; Giampapa, Mark E. (Irvington, NY) [Irvington, NY; Heidelberger, Philip (Cortlandt Manor, NY) [Cortlandt Manor, NY; Steinmacher-Burow, Burkhard D. (Mount Kisco, NY) [Mount Kisco, NY; Takken, Todd E. (Mount Kisco, NY) [Mount Kisco, NY; Vranas, Pavlos M. (Bedford Hills, NY) [Bedford Hills, NY

2009-09-08

155

Routing in Unreliable Networks.  

National Technical Information Service (NTIS)

Consider strategies for selecting message routes in unreliable data communication networks. The following assumptions are made: the nodes of the network are perfectly reliable; the links are unreliable, and for each link l there is a probability P sub l, ...

I. M. Figueredo

1986-01-01

156

Surface modification of vesicles with methylol urea  

Microsoft Academic Search

Surface-modified vesicles were prepared using N-[3-(dimethylamino)propyl]-octadecanamide and stearic acid as bilayer-forming lipids, and N-methylol urea-dodecylamine conjugated (MU-DOA) as a surface modifier. The conjugation of MU to DOA was confirmed by FTIR\\u000a spectra. MU-DOA was incorporated into the vesicles by co-homogenization of the lipids and MU-DOA, and the incorporated MU-DOA\\u000a was then reacted with MU in aqueous bulk phase through a

Jin-Chul Kim; Jong-Duk Kim

2002-01-01

157

Urea formaldehyde foam: a dangerous insulation  

SciTech Connect

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.

Keough, C.

1980-12-01

158

Functional Nanomaterials from Bis-urea Macrocycles  

NASA Astrophysics Data System (ADS)

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. In one unit cell, two silver atoms are 3.13 A apart suggesting a very interesting Ag-Ag bond interaction. We probed the Ag-Ag interaction by solid-state spectroscopic techniques as well as ESI-MS and Raman spectroscopy. The results indicate that there is indeed an interaction between the two silver atoms and their proximity is not merely a packing artifact.

Dawn, Sandipan

159

Urea hydrolysis and calcium carbonate reaction fronts  

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

160

Industrial Vehicle Routing  

Microsoft Academic Search

Solving the Vehicle Routing Problem (VRP) is a key to efficiency in transportation and supply chain management. The VRP is\\u000a an NP-hard problem that comes in many guises. The VRP literature contains thousands of papers, and VRP research is regarded\\u000a as one of the great successes of OR. Vehicle routing decision support tools provide substantial savings in society every day,

Geir Hasle; Oddvar Kloster

161

21 CFR 862.1770 - Urea nitrogen test system.  

Code of Federal Regulations, 2012 CFR

...ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES CLINICAL CHEMISTRY AND CLINICAL TOXICOLOGY DEVICES Clinical Chemistry Test Systems § 862.1770 Urea nitrogen test system. (a)...

2012-04-01

162

Guppies, toadfish, lungfish, coelacanths and frogs: a scenario for the evolution of urea retention in fishes  

Microsoft Academic Search

The question of how (and why) the ureosmotic strategy, characteristic of Latimeria chalumnae and the chondrichthians evolved is addressed. There are three requirements for ureosmotic regulation: urea synthesis via the ornithine-urea cycle, urea tolerance involving biochemical and physiological adjustments, and urea retention that requires renal, branchial, metabolic and reproductive adaptations. Several examples of lower vertebrates in which urea plays a

Robert W. Griffith

1991-01-01

163

Combustion 2000  

SciTech Connect

This report is a presentation of work carried out on Phase II of the HIPPS program under DOE contract DE-AC22-95PC95144 from June 1995 to March 2001. The objective of this report is to emphasize the results and achievements of the program and not to archive every detail of the past six years of effort. These details are already available in the twenty-two quarterly reports previously submitted to DOE and in the final report from Phase I. The report is divided into three major foci, indicative of the three operational groupings of the program as it evolved, was restructured, or overtaken by events. In each of these areas, the results exceeded DOE goals and expectations. HIPPS Systems and Cycles (including thermodynamic cycles, power cycle alternatives, baseline plant costs and new opportunities) HITAF Components and Designs (including design of heat exchangers, materials, ash management and combustor design) Testing Program for Radiative and Convective Air Heaters (including the design and construction of the test furnace and the results of the tests) There are several topics that were part of the original program but whose importance was diminished when the contract was significantly modified. The elimination of the subsystem testing and the Phase III demonstration lessened the relevance of subtasks related to these efforts. For example, the cross flow mixing study, the CFD modeling of the convective air heater and the power island analysis are important to a commercial plant design but not to the R&D product contained in this report. These topics are of course, discussed in the quarterly reports under this contract. The DOE goal for the High Performance Power Plant System ( HIPPS ) is high thermodynamic efficiency and significantly reduced emissions. Specifically, the goal is a 300 MWe plant with > 47% (HHV) overall efficiency and {le} 0.1 NSPS emissions. This plant must fire at least 65% coal with the balance being made up by a premium fuel such as natural gas. 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 issues of fabrication and reliability, availability and maintenance. The program that has s

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

164

Chemical deactivation of V 2O 5\\/WO 3–TiO 2 SCR catalysts by additives and impurities from fuels, lubrication oils, and urea solution  

Microsoft Academic Search

The influence of the combustion products of different lubrication oil additives (Ca, Mg, Zn, P, B, Mo) and impurities in Diesel fuel (K from raps methyl ester) or urea solution (Ca, K) on the activity and selectivity of vanadia-based SCR catalysts were investigated. Standard V2O5\\/WO3–TiO2 catalysts coated on metal substrates (400cpsi) were impregnated with water soluble compounds of these elements

Oliver Kröcher; Martin Elsener

2008-01-01

165

DEVELOPMENT OF ACTIVATED CARBONS FROM COAL COMBUSTION BY-PRODUCTS  

Microsoft Academic Search

The implementation of increasingly stringent Clean Air Act Regulations by the coal utility industry has resulted in an increase in the concentration of unburned carbon in coal combustion fly ash. In 1999, around 6 million tons of unburned carbon were disposed in the US, due to the present lack of efficient routes for its utilization. However, unburned carbon is a

Harold H. Schobert; M. Mercedes Maroto-Valer; Zhe Lu

2001-01-01

166

Internal combustion engine method for delayed reaction stratified combustion  

Microsoft Academic Search

A method of delayed reaction stratified combustion for internal combustion engines comprising burning a compressed fast burning rich air-fuel mixture during an initial portion of a combustion event, adding supplemental diluting air optimally with recirculated exhaust gas (EGR) during an intermediate portion of such combustion event and completing combustion during latter portions of the combustion event. Suggested timing and mixture

Cataldo

1984-01-01

167

Fundamentals of Gas Turbine combustion  

NASA Technical Reports Server (NTRS)

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.

Gerstein, M.

1979-01-01

168

Urea transporter UT3 functions as an efficient water channel. Direct evidence for a common water/urea pathway.  

PubMed

A family of molecular urea transporters (UTs) has been identified whose members appear to have an exceptionally high transport turnover rate. To test the hypothesis that urea transport involves passage through an aqueous channel, osmotic water permeability was measured in Xenopus oocytes expressing UTs. The UT3 class of urea transporters functioned as efficient water channels. Quantitative measurement of single channel water permeability (pf) using epitope-tagged rat UTs gave pf (in cm3/s x 10(-14)) of 0.14 +/- 0.11 (UT2) and 1.4 +/- 0.2 (UT3), compared with 6.0 and 2.3 for water channels AQP1 and AQP3, respectively. Relative single channel urea permeabilities (purea) were 1.0 (UT2), 0.44 (UT3), and 0.0 (AQP1). UT3-mediated water and urea transport were weakly temperature-dependent (activation energy <4 kcal/mol), inhibited > 75% by the urea transport inhibitor 1,3-dimethylthiourea, but not inhibited by the water transport inhibitor HgCl2. To test for a common water/urea pore, the urea reflection coefficient (sigmaurea) was measured by independent induced osmosis and solvent drag methods. In UT3-expressing oocytes, the time course of oocyte volume in response to different urea gradients (induced osmosis) gave sigmaurea approximately 0.3 for the UT3 pathway, in agreement with sigmaurea determined by the increase in uptake of [14C]urea during osmotic gradient-induced oocyte swelling (solvent drag). In oocytes of comparable water and urea permeability coexpressing AQP1 (permeable to water, not urea) and UT2 (permeable to urea, not water), sigmaurea = 1. These results indicate that UT3 functions as a urea/water channel utilizing a common aqueous pathway. The water transporting function and low urea reflection coefficient of UT3 in vasa recta may be important for the formation of a concentrated urine by countercurrent exchange in the kidney. PMID:9545259

Yang, B; Verkman, A S

1998-04-17

169

Further Observations on Utilization of Urea by Lactating Cows  

Microsoft Academic Search

Two experiments measured utilization of urea by lactating eows by intake, milk production, nitrogen balance and related characteristics. In each experiment, 36 cows were in a factorial arrangement of treatments. In Experiment 1, concentrates containing 12, 17, and 22% crude protein equivalent were fed both with and without 1.5% urea (4.2% crude protein). Con- centrate was fed at one unit

F. N. Knott; C. E. Polan; J. T. Huber

1972-01-01

170

The uptake of urea by natural populations of marine phytoplankton  

Microsoft Academic Search

ARSTlWCT Nitrogen-15 isotopes were used to study the uptake of nitrate, ammoninm, and urea by natural phytoplankton populations in 36 samples collected at nine stations off the coast of southern California. The percentage of the total phytoplankton nitrogen productivity accounted for by urea varied From SOc\\/, and for the entire study averaged 28%. The percentage of total available

James J. McCarthy

1972-01-01

171

DFT study of urea interaction with potassium chloride surfaces  

Microsoft Academic Search

In this work, interaction of urea on the important surfaces of potassium chloride has been investigated using density functional theory (DFT) approach. We have performed the DFT calculations using slab models for the interactions of urea with {100}, {110} and {111} surfaces of KCl. Furthermore, the influence of solvent effect was computed with the COSMO continuum model. While sodium chloride

Ajeet Singh; Bishwajit Ganguly

2008-01-01

172

Effect of Divalent Cations on 'Chlorella fusca' Grown on Urea.  

National Technical Information Service (NTIS)

Chlorella fusca var. vacuolata was used as a test organism for the present study. Urea was found to be a better nitrogen source for the growth of Chlorella than either nitrate or ammonium. The increase in growth in the presence of urea was about 1.7 fold ...

A. B. Innam R. A. Yehya I. M. Shehab

1987-01-01

173

Model of an immobilized enzyme conductimetric urea biosensor  

Microsoft Academic Search

A model for predicting the response of a conductimetric urea biosensor was developed and validated experimentally. The biosensor under consideration is formed by immobilizing the enzyme urease onto the surface of a planar interdigitated electrode array. The enzymatic hydrolysis of urea produces ionic products, such as ammonium and bicarbonate ions, which increase the electrical conductivity of the solution proximal to

Anthony Guiseppi-Elie

1996-01-01

174

Reactions of Urea with Carbohydrazide Reaktionen von Harnstoff MIT Carbohydrazid.  

National Technical Information Service (NTIS)

Chemical reactions of urea and carbohydrazide were investigated in smelts and aqueous solutions. Urea and carbohydrazide were converted in molar ratios 1:1, 2:1, and 1:2 in the smelt and in an aqueous solution. The reactions in the smelt up to 140 C lead ...

W. Engel

1972-01-01

175

Molecular Basis of the Apparent Near Ideality of Urea Solutions.  

SciTech Connect

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.

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

2007-11-01

176

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

Code of Federal Regulations, 2012 CFR

...2012-04-01 false Urea-formaldehyde resins in molded articles. 177.1900 Section...Surfaces § 177.1900 Urea-formaldehyde resins in molded articles. Urea-formaldehyde resins may be safely used as the...

2012-04-01

177

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

Code of Federal Regulations, 2011 CFR

...2011-04-01 false Urea-formaldehyde resins in molded articles. 177.1900 Section...Surfaces § 177.1900 Urea-formaldehyde resins in molded articles. Urea-formaldehyde resins may be safely used as the...

2011-04-01

178

76 FR 78885 - Solid Urea From the Russian Federation and Ukraine: Continuation of Antidumping Duty Orders  

Federal Register 2010, 2011, 2012, 2013

...A-823-801] Solid Urea From the Russian Federation and Ukraine: Continuation of...orders on solid urea from the Russian Federation (Russia) and Ukraine would likely lead...See Solid Urea From the Russian Federation and Ukraine: Final...

2011-12-20

179

40 CFR 418.30 - Applicability; description of the urea subcategory.  

Code of Federal Regulations, 2010 CFR

...true Applicability; description of the urea subcategory. 418.30 Section 418...FERTILIZER MANUFACTURING POINT SOURCE CATEGORY Urea Subcategory § 418.30 Applicability; description of the urea subcategory. The provisions of...

2010-07-01

180

40 CFR 418.30 - Applicability; description of the urea subcategory.  

Code of Federal Regulations, 2010 CFR

...false Applicability; description of the urea subcategory. 418.30 Section 418...FERTILIZER MANUFACTURING POINT SOURCE CATEGORY Urea Subcategory § 418.30 Applicability; description of the urea subcategory. The provisions of...

2009-07-01

181

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

Code of Federal Regulations, 2010 CFR

... 2009-04-01 2009-04-01 false Urea-formaldehyde resins in molded articles...Repeated Use Food Contact Surfaces § 177.1900 Urea-formaldehyde resins in molded articles. Urea-formaldehyde resins may be safely...

2009-04-01

182

40 CFR 418.30 - Applicability; description of the urea subcategory.  

Code of Federal Regulations, 2013 CFR

...true Applicability; description of the urea subcategory. 418.30 Section 418...FERTILIZER MANUFACTURING POINT SOURCE CATEGORY Urea Subcategory § 418.30 Applicability; description of the urea subcategory. The provisions of...

2013-07-01

183

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

Code of Federal Regulations, 2013 CFR

...2013-07-01 false Amine-modified urea-formaldehyde polymer (generic). ...Substances § 721.10533 Amine-modified urea-formaldehyde polymer (generic). ...identified generically as amine-modified urea-formaldehyde polymer (PMN...

2013-07-01

184

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

Code of Federal Regulations, 2013 CFR

...2013-07-01 2013-07-01 false Urea, (hexahydro-6-methyl-2-oxopyrimidinyl...Specific Chemical Substances § 721.9920 Urea, (hexahydro-6-methyl-2-oxopyrimidinyl...reporting. (1) The chemical substance urea,...

2013-07-01

185

New Combustion Processes.  

National Technical Information Service (NTIS)

The purpose of the report is to present material related to unconventional combustion processes which might be used in the development of hypersonic ramjet and supersonic combustion processes. A literature search revealed one article directly related to s...

1964-01-01

186

Combustion Hydrodynamics and Chemistry.  

National Technical Information Service (NTIS)

Accomplishments in combustion hydrodynamics and chemistry studies consisted of a computational study of the chemical kinetics of hydrogen combustion along with some subsidiary studies and programming. Comparisons with experimental results have been genera...

E. Hyman

1981-01-01

187

Fuels, combustion, and lubrication  

SciTech Connect

This book contains the proceeding of this ASME in fuels, combustion, and lubrication. Topics covered include: combustion efficiency on residual fuels; marine diesel lubricants; uses and abuses; synthetic lubricants for high output medium-speed diesels.

Goyal, M.R. (John Deere Product Engineering Center (US))

1990-01-01

188

Lithium Combustion: A Review.  

National Technical Information Service (NTIS)

This review deals with the chemical reactions, ignition, and combustion of lithium combustion in air and in the components of air, including oxygen, nitrogen, water, and carbon dioxide. It was found that lithium reacts vigorously with these substances. In...

R. A. Rhein

1990-01-01

189

Internal combustion engine with dual combustion chambers  

Microsoft Academic Search

This patent describes a spark-ignition. The overhead valve type internal combustion engine comprises: a cylinder closed at the top by a semi-spherical cylinder head; a piston reciprocating within the cylinder with the piston; cylinder and cylinder head defining at least one combustion chamber; and wherein the cylinder head includes an intake valve aperture, an exhaust valve aperture, and a spark

Simay

1987-01-01

190

Structure and permeation mechanism of a mammalian urea transporter  

PubMed Central

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 ?. 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.

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

2012-01-01

191

Postmortem Blood Sugar and Blood Urea Nitrogen Determinations  

PubMed Central

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

Fekete, John F.; Kerenyi, Norbert A.

1965-01-01

192

Combustion oscillation control  

SciTech Connect

Premixing of fuel and air can avoid high temperatures which produce thermal NOx, but oscillating combustion must be eliminated. Combustion oscillations can also occur in Integrated Gasification Combined Cycle turbines. As an alternative to design or operating modifications, METC is investigating active combustion control (ACC) to eliminate oscillations; ACC uses repeated adjustment of some combustion parameter to control the variation in heat release that drives oscillations.

Richards, G.A.; Janus, M.C.

1996-12-31

193

Pyrolysis combustion flow calorimetry  

Microsoft Academic Search

A method for evaluating the combustibility of milligram samples is described. Pyrolysis-combustion flow calorimetry (PCFC) separately reproduces the solid state and gas phase processes of flaming combustion in a nonflaming test by controlled pyrolysis of the sample in an inert gas stream followed by high temperature oxidation of the volatile pyrolysis products. Oxygen consumption calorimetry is used to measure the

Richard E Lyon; Richard N Walters

2004-01-01

194

Functionalized multilayered graphene platform for urea sensor.  

PubMed

Multilayered graphene (MLG) is an interesting material for electrochemical sensing and biosensing because of its very large 2D electrical conductivity and large surface area. We propose a less toxic, reproducible, and easy method for producing functionalized multilayer graphene from multiwalled carbon nanotubes (MWCNTs) in mass scale using only concentrated H(2)SO(4)/HNO(3). Electron microscopy results show the MLG formation, whereas FTIR and XPS data suggest its carboxylic and hydroxyl-functionalized nature. We utilize this functionalized MLG for the fabrication of a novel amperometric urea biosensor. This biosensor shows linearity of 10-100 mg dL(-1), sensitivity of 5.43 ?A mg(-1) dL cm(-2), lower detection limit of 3.9 mg dL(-1), and response time of 10 s. Our results suggest that MLG is a promising material for electrochemical biosensing applications. PMID:22117758

Srivastava, Rajesh K; Srivastava, Saurabh; Narayanan, Tharangattu N; Mahlotra, Bansi D; Vajtai, Robert; Ajayan, Pulickel M; Srivastava, Anchal

2012-01-24

195

Solution combustion synthesis of MgAl 2O 4 using fuel mixtures  

Microsoft Academic Search

The paper reveals a new perspective concerning the rational fuel selection and the logical elaboration of the recipes for the MgAl2O4 solution combustion synthesis. It was shown that Mg(NO3)2·6H2O and Al(NO3)3·9H2O exhibit different behavior with respect to urea, glycine and ?-alanine. Urea proved to be the most adequate fuel for Al(NO3)3·9H2O, while ?-alanine proved to be the most appropriate fuel

Robert Iano?; Ioan Laz?u; Cornelia P?curariu; Paul Barvinschi

2008-01-01

196

Ethylated Urea - Ether - Modified Urea - Formaldehyde Resins, Part I: Structural and Physicochemical Properties  

Microsoft Academic Search

First, phenol - formaldehyde (PF) and urea - formaldehyde (UFII) resins were separately conventionally prepared in our laboratory. Also, UF resin synthesized from the acid modified synthesis procedure was synthesized in a purely acid medium of pH 1.0, FU molar ratio of 1.0 and at 50oC (one-stage acid modified-synthesis procedure). Subsequently, the UF resin II was modified during synthesis by

Mathew Obichukwu EDOGA

197

Combustion and core noise  

NASA Astrophysics Data System (ADS)

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.

Mahan, J. Robert; Karchmer, Allen

1991-08-01

198

Vehicle Routing Problem with Time Windows: Minimizing Route Duration.  

National Technical Information Service (NTIS)

The author investigates the implementation of edge-exchange improvement methods for the vehicle routing problem with time windows with minimization of route duration as the objective. The presence of time windows as well as the chosen objective cause veri...

M. W. P. Savelsbergh

1991-01-01

199

Routing of multipoint connections  

Microsoft Academic Search

The author addresses the problem of routing connections in a large-scale packet-switched network supporting multipoint communications. He gives a formal definition of several versions of the multipoint problem, including both static and dynamic versions. He looks at the Steiner tree problem as an example of the static problem and considers the experimental performance of two approximation algorithms for this problem.

BERNARD M. WAXMAN

1988-01-01

200

Commuters route choice behaviour  

Microsoft Academic Search

The paper reports laboratory experiments with a two route choice scenario. In each session 18 subjects had to choose between a main road M and a side road S. The capacity of M was larger. Feedback was given in treatment I only on the subjects' own travel time and in treatment II on travel time for M and S. The

R. Selten; T. Chmura; T. Pitz; S. Kube; M. Schreckenberg

2007-01-01

201

Hydrologic Flood Routing.  

ERIC Educational Resources Information Center

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)

Heggen, Richard J.

1982-01-01

202

Aqueous urea solution destabilizes A?16–22 oligomers  

PubMed Central

We use long multiple trajectories generated by molecular dynamics simulations to probe the stability of oligomers of A?16–22 (KLVFFAE) peptides in aqueous urea solution. High concentration of urea promotes the formation of ?-strand structures in A?16–22 monomers, whereas in water they adopt largely compact random coil structures. The tripeptide system, which forms stable antiparallel ?-sheet structure in water, is destabilized in urea solution. The enhancement of ?-strand content in the monomers and the disruption of oligomeric structure occur largely by direct interaction of urea with the peptide backbone. Our simulations suggest that the oligomer unbinding dynamics is determined by two opposing effects, namely, by the increased propensity of monomers to form ?-strands and the rapid disruption of the oligomers. The qualitative conclusions are affirmed by using two urea models. Because the proposed destabilization mechanism depends largely on hydrogen bond formation between urea and the peptide backbone, we predict that high urea concentration will destabilize oligomers of other amyloidogenic peptides as well.

Klimov, D. K.; Straub, John E.; Thirumalai, D.

2004-01-01

203

Opportunities in pulse combustion  

SciTech Connect

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.

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

1985-10-01

204

Molecular Mechanisms of Urea Transport in Health and Disease  

PubMed Central

In the late 1980s, urea permeability measurements produced values that could not be explained by paracellular transport or lipid phase diffusion. The existence of urea transport proteins were thus proposed and less than a decade later, the first urea transporter was cloned. The SLC14A family of urea transporters has two major subgroups, designated SLC14A1 (or UT-B) and Slc14A2 (or UT-A). UT-B and UT-A gene products are glycoproteins located in various extra-renal tissues however, a majority of the resulting isoforms are found in the kidney. The UT-B (Slc14A1) urea transporter was originally isolated from erythrocytes and two isoforms have been reported. In kidney, UT-B is located primarily in the descending vasa recta. The UT-A (Slc14A2) urea transporter yields 6 distinct isoforms, of which 3 are found chiefly in the kidney medulla. UT-A1 and UT-A3 are found in the inner medullary collecting duct (IMCD), while UT-A2 is located in the thin descending limb. These transporters are crucial to the kidney’s ability to concentrate urine. The regulation of urea transporter activity in the IMCD involves acute modification through phosphorylation and subsequent movement to the plasma membrane. UT-A1 and UT-A3 accumulate in the plasma membrane in response to stimulation by vasopressin or hypertonicity. Long term regulation of the urea transporters in the IMCD involves altering protein abundance in response to changes in hydration status, low protein diets, or adrenal steroids. Urea transporters have been studied using animal models of disease including diabetes mellitus, lithium intoxication, hypertension, and nephrotoxic drug responses. Exciting new genetically engineered mouse models are being developed to study these transporters.

Klein, Janet D.; Blount, Mitsi A.; Sands, Jeff M.

2012-01-01

205

Combustion Processes Under Microgravity Conditions  

NASA Astrophysics Data System (ADS)

Introduction Classification of Combustion Processes Premixed Flames Diffusion Flames Condensed-Fuel Combustion Flame Balls Alcohol Droplet Combustion Alcohol Combustion Chemistry Methanol Flame Extinction Potential Resolution of a Paradox Other Combustion Phenomena Learned from Experiments Under Microgravity - Conditions Combustion Topics of Future Promise for Microgravity Investigation Premixed-Flame Instabilities Flammability Limits Ignition Flame Extinction Soot Production Flame Spread Along Fuel Rods Pollutant Production in Combustion Conclusions

Williams, F. A.

206

Trusted Greedy Perimeter Stateless Routing  

Microsoft Academic Search

Ad-hoc networks generally comprise of mobile wireless nodes having limited communication and computation resources. These nodes execute special routing protocols, which help to establish multi-hop communication despite a dynamic topology. The greedy perimeter stateless routing (GPSR) protocol is one such routing protocol that is frequently used to establish routes in an ad-hoc or sensor network. However, for its precise execution,

Asad Amir Pirzada; Chris McDonald

2007-01-01

207

Throughput of Wavelength Routing Networks.  

National Technical Information Service (NTIS)

We consider the problem of interconnecting N local area networks (LANs) through a wavelength routing all optical network (wavelength-routing AON) supporting F wavelengths at R b/s per wavelength. A wavelength-routing AON is one in which the path of a sign...

P. A. Humblet R. A. Barry

1994-01-01

208

Online Routing in Convex Subdivisions  

Microsoft Academic Search

We consider online routing algorithms for nding paths between the vertices of plane graphs. We show (1) there exists a routing algorithm for arbitrary triangulations that has no memory and uses no randomization, (2) no equivalent result is possible for convex subdivisions, (3) there is no competitive online routing algorithm under the Euclidean distance metric in arbitrary triangulations, and (4)

Prosenjit Bose; Pat Morin; Andrej Brodnik; Svante Carlsson; Erik D. Demaine; Rudolf Fleischer; J. Ian Munro; Alejandro López-ortiz

2000-01-01

209

Structure study of cellulose fibers wet-spun from environmentally friendly NaOH/urea aqueous solutions.  

PubMed

In this study, structure changes of regenerated cellulose fibers wet-spun from a cotton linter pulp (degree of polymerization approximately 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 H2SO4/Na2SO4 aqueous solution at 15 degrees 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, Rg, of about 232 nm and an apparent hydrodynamic radius, Rh, 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. PMID:17472335

Chen, Xuming; Burger, Christian; Wan, Fen; Zhang, Jun; Rong, Lixia; Hsiao, Benjamin S; Chu, Benjamin; Cai, Jie; Zhang, Lina

2007-06-01

210

Online measurement of urea concentration in spent dialysate during hemodialysis  

NASA Astrophysics Data System (ADS)

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

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

2002-05-01

211

Photodegradation of MDI Based Polyurethane/Urea Elastomers.  

National Technical Information Service (NTIS)

A series of polyurethane urea and polyurea elastomers based on MDI, a chain extender such as ethylene glycol or ethylene diamine, and polyethylene glycol oligomers or amine end capped modified polyethylene glycol oligomers were synthesized and characteriz...

C. E. Hoyle H. Shah K. Moussa P. Berry I. B. Rufus

1993-01-01

212

Reinvestigation of growth of thiourea urea zinc sulfate crystal.  

PubMed

Reinvestigation of the growth of thiourea urea zinc sulfate crystal is reported. Aqueous reaction of thiourea, urea and zinc sulfate in 1:1:1 mol ratio results in the formation of the well known [Zn(tu)3(SO4)] (1) (tu=thiourea) crystal and not the 'so called' novel semiorganic nonlinear optical thiourea urea zinc sulfate (2) crystal, as claimed by Redrothu Hanumantha Rao, S. Kalainathan, Spectroscopic investigation, nucleation, growth, optical, thermal and second harmonic studies of novel semi-organic nonlinear optical crystal - Thiourea urea zinc sulfate, Spectrochim. Acta A97 (2012) 456-463. In this work, we demonstrate the usefulness of elemental analytical data, infrared and NMR spectra and X-ray powder pattern, for accurate product characterization. PMID:24060627

Srinivasan, Bikshandarkoil R; Naik, Teja A; Tylczy?ski, Zbigniew; Priolkar, K R

2014-01-01

213

Formation of urea and guanidine by irradiation of ammonium cyanide.  

NASA Technical Reports Server (NTRS)

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.

Lohrmann, R.

1972-01-01

214

Foliar applications of Lo-Biuret Urea and Potassium Phosphite to Navel Orange trees  

Microsoft Academic Search

This experiment was established in January 2000 in a block of 'Washington' navel orange trees at Verde Growers, Stanfield, AZ. Treatments included: normal grower practice, winter low biuret (LB) urea application, summer LB urea application, winter LB urea application plus winter and spring potassium phosphite, winter LB urea application plus summer potassium phosphite, and normal grower practice plus spring potassium

Glenn Wright; James Walworth

215

Permeability of medullary nephron segments to urea and water: Effect of vasopressin  

Microsoft Academic Search

Permeability of medullary nephron segments to urea and water: Effect of vasopressin. High papillary urea concentrations are necessary for the formation of maximally concentrated urine, while low papillary urea concentrations are associated with less concentrated urine. In the present studies we examined the membrane characteristics that are important in determining the medullary urea concentration profiles. Using isolated segments of rabbit

Antonino S Rocha; Juha P Kokko

1974-01-01

216

An evaluation of urea-rubber matrices as slow-release fertilizers  

Microsoft Academic Search

The viability of a ‘urea-rubber matrix’ (URM) as a slow-release nitrogen fertilizer was assessed by field trials and incubation studies. Encapsulation of urea in the rubber matrix apparently prevented the inhibition of seed germination experienced at high temperatures (> 20°C) following high urea applications. The release of urea from URM increased with temperature and was well described by a diffusion

Z. A. Hassan; S. D. Young; C. Hepburn; R. Arizal

1990-01-01

217

Urea loading enhances postfreeze performance of frog skeletal muscle  

Microsoft Academic Search

The wood frog (Rana sylvatica) is a terrestrial hibernator that can accumulate urea as an osmoprotectant in autumn and winter. This study tested the hypothesis\\u000a that elevated urea can also function as a cryoprotectant in this freeze-tolerant species. Performance characteristics (threshold\\u000a stimulus voltage, maximal isometric twitch and tetanic contraction forces, and ½ fatigue time) of isolated gastrocnemius muscles\\u000a were measured

Jon P. Costanzo; Marina Marjanovic; Elizabeth A. Fincel; Richard E. Lee Jr

2008-01-01

218

Solid-state urea biosensor based on the differential method  

Microsoft Academic Search

In this paper, the solid-state urea biosensor was successfully fabricated based on the differential method, which contains three parts: the SnO2\\/ITO glass electrode used as the pseudoreference electrode; the SnO2\\/ITO glass electrode used as the contrast electrode; and the urease\\/SnO2\\/ITO glass electrode used as the enzyme electrode. Correspondingly, this solid-state urea biosensor was fabricated based on the SnO2\\/ITO glass electrode,

Chung-We Pan; Jung-Chuan Chou; Tai-Ping Sun; Shen-Kan Hsiung

2006-01-01

219

[Clinical experiences of interval treatment with dermatologic agents containing urea].  

PubMed

Topical vehicles containing urea are increasingly used in dermatology because of their favorable pharmacological properties, which are due to the following capacities of urea: (1) its beneficial influence on the structure and physiology of the skin, and (2) its therapeutic effect in combination with other topically active agents in various skin diseases, such as psoriasis, ichthyosis, and chronic eczema. Our own experiences presented here are in accordance with these statements. PMID:2284833

Petres, J; Antal, I; Füzesi, S

1990-08-01

220

Experience with Urea-Resin Stabilization of Soils  

Microsoft Academic Search

In construction practice, the procedure of injecting gel-forming grout into soil after its pretreatment is currently used primarily for the urea-resin stabilization of sandy soils where hydrochloric and oxalic acids are mainly used as hardeners. The Scientific-Research Institute of Foundations and Underground Structures has developed new formulas based on urea resin and the following complex hardeners: Fe 2 (SO 4

N. A. Bleskina

2005-01-01

221

Corncobs as Energy with Urea Nitrogen in Dairy Rations1  

Microsoft Academic Search

Sixteen dairy cows over two con- secutive 305-day lactations were used to evaluate a diet containing urea, corncobs, and other by-products unsuitable for human consumption. The control ration contained mostly soybean meal, corn, corn silage, and alfalfa. Dry matter digestibilities were 55.4 and 68.6% for urea-cob and standard diets. Apparent digestibility of cobs fed as 87 to 94% of total

S. C. Peyton; H. R. Conrad

1982-01-01

222

Characterisation of structured hydrolysis catalysts for urea-SCR  

Microsoft Academic Search

In the current study the performance of different substrates with respect to pressure drop, mixing between catalyst channels\\u000a and urea conversion efficiency were measured. An increase of the volumetric conversion efficiency was found when structured\\u000a substrates were applied. Also the use of solid-urea aerosol was compared to the AdBlue technology and found to be a promising alternative.

Sebastian Steinbach; Jürgen Grünwald; Udo Glückert; Thomas Sattelmayer

2007-01-01

223

Coal combustion products  

SciTech Connect

Coal-burning power plants, which supply more than half of US electricity, also generate coal combustion products, which can be both a resource and a disposal problem. The US 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. 5 refs., 5 figs.

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

2001-08-15

224

Supersonic combustion engine and method of combustion initiation and distribution  

SciTech Connect

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

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

1993-06-29

225

Droplet Combustion Experiment  

NASA Technical Reports Server (NTRS)

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

Nayagam, Vedha

1998-01-01

226

Plasma Route to Nanosciences and Nanotechnology Frontiers  

Microsoft Academic Search

In this paper, I will discuss different routes to preparation of nanomaterials. The biological route provided in nature, chemical route and plasma route are indicated. The plasma route to prepare nanomaterials as compared to chemical route is highlighted. In particular, the plasma method, making use of Dense Plasma Focus device (DPF) to prepare nanomaterials is discussed. A 3.3 KJ, Mather

M. P. SRIVASTAVA

2009-01-01

227

Prediction of Ammonia Emission from Dairy Cattle Manure Based on Milk Urea Nitrogen: Relation of Milk Urea Nitrogen to Urine Urea Nitrogen Excretion  

Microsoft Academic Search

ABSTRACT The objectives of this study,were,to assess,the rela- tionship,between,urinary,urea N (UUN) excretion,(g\\/ d) and,milk urea N (MUN; mg\\/dL) and to test whether the relationship,was,affected by stage of lactation and thedietarycrudeprotein(CP)content.Twelvelactating multiparous,Holstein cows were randomly,selected and blocked,into 3 groups,of 4 cows,intended,to represent early [123 ± 26 d in milk (DIM); mean,± standard,devia- tion], mid (175 ± 3 DIM), and late (221

S. A. Burgos; J. G. Fadel; E. J. DePeters

2007-01-01

228

EVALUATION OF UREA FERTILIZERS AND UREASE INHIBITORS FOR CORN AND WHEAT PRODUCTION (PHOSPHOROAMIDE, HYDROLYSIS)  

Microsoft Academic Search

Urea is the major solid N fertilizer in world agriculture, however, ammonia volatilization from surface-applied urea fertilizers can result in urea producing lower crop yields than other N fertilizers. Urease inhibitors retard urea hydrolysis and, in laboratory studies, reduce ammonia volatilization loss from urea fertilizers.^ Six phosphoroamide urease inhibitors trichloroethyl phosphorodiamidate, diethyl phosphoric triamide, dimethyl phosphoric triamide, N-(diaminophosphinyl)-cyclohexylamine, N-benzyl-N-methyl phosphoric

ALAN JAY SCHLEGEL

1985-01-01

229

Absorption of molecular urea by rice under flooded and non-flooded soil conditions  

Microsoft Academic Search

A pot experiment was conducted with rice to study the relative absorption of urea in molecular form compared to the other\\u000a forms of N produced in soil from the applied urea. A method involving application of 14C-labelled urea and 15N-labelled urea alternately in two splits was used to quantify the absorption of molecular urea and other forms of N formed

A. N. Safeena; P. A. Wahid; P. V. Balachandran; M. S. Sachdev

1999-01-01

230

Determination of Air Volume Flows Required for Dilution of Flue Gases to a Concentration at Which Safety and Visibility Is Assured in Escape Routes. Pt. 1.  

National Technical Information Service (NTIS)

Investigations on maximum permissible flue gas concentrations in escape routes were carried out in a special experimental facility, i.e. a cubic combustion space with an edge length of 2.5m in which mass losses during combustion were measured by means of ...

R. John

1982-01-01

231

Diurnal Variation of Rumen Ammonia, Serum Urea, and Milk Urea in Dairy Cows at High and Low Yields1  

Microsoft Academic Search

ABSTRACT Milk urea content as an indicator of nutritional status may,be a useful tool if major,sources of variation are consid- ered. Blood and milk samples were col- lected frequently during 16 to 19 h from four Holstein cows to study diurnal vari- ation of urea content. Corn silage, alfalfa hay, and concentrates were fed. Rumen ammonia, VFA, and pH were

D. L. Palmquist

1993-01-01

232

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

SciTech Connect

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.

Sahu, J.N.; Gangadharan, P.; Patwardhan, A.V.; Meikap, B.C. [Indian Institute of Technology, Kharagpur (India). Dept. of Chemical Engineering

2009-01-15

233

Minimal sampling protocol for accurate estimation of urea production: a study with oral [ 13C]urea in fed and fasted piglets  

Microsoft Academic Search

BACKGROUND & AIMS: An oral [13C]urea protocol may provide a simple method for measurement of urea production. The validity of single pool calculations in relation to a reduced sampling protocol was assessed. METHODS: In eight fed and five fasted piglets, plasma urea enrichments from a 10 h sampling protocol were measured following an intragastric [13C]urea bolus. Blood [13C]bicarbonate was measured

Michiel J. S. Oosterveld; Reinoud J. B. J. Gemke; Jack R. Dainty; Willem Kulik; Cornelis Jakobs; Meer van der K

2005-01-01

234

Effect of Addition of Urea or Urea Plus Molasses to Different Corn Silages Harvested at Dough Stage on Silage Quality and Digestible Dry Matter Yield  

Microsoft Academic Search

Demirel, M., Yilmaz, ?., Deniz, S., Kaplan, O. and Akdeniz, H. 2003. Effect of addition of urea or urea plus molasses to different corn silages harvested at dough stage on silage quality and digestible dry matter yield. J. Appl. Anim. Res., 24: 7–16.To study the effects of 0.5% urea, and 0.5% urea plus 4% molasses addition to different corn silages

Murat Demirel; ?brahim Yilmaz; Suphi Deniz; Oktay Kaplan; Hakki Akdeniz

2003-01-01

235

Combustion synthesis and optical properties of ceria doped gadolinium-oxide nanopowder  

NASA Astrophysics Data System (ADS)

The Ceria doped Gadolinium (Gd2O3) nanopowder was synthesized by combustion synthesis by using urea as a fuel. The combustion synthesis method which is reported here is advantageous from the perspectives of small size of the nanoparticle. The structural and photoluminescence (PL) property of sample was studies. Gd2O3:Ce3+ nanoparticles exhibit green emission around 543 nm. The result of XRD show that synthesized sample has cubic structure. The average size of particle is found to be 45 nm. The surface morphology of the films is also presented.

Tamrakar, Raunak Kumar; Bisen, D. P.

2013-06-01

236

Solution combustion synthesis and optimization of phosphors for plasma display panels  

NASA Astrophysics Data System (ADS)

The optimization of primary phosphors required for display panels were carried out. Phosphors were synthesized by simple solution combustion technique. The synthesis is based on the exothermic reaction between the fuel (urea) and oxidizer (ammonium nitrate).The heat generated in the reaction is used for auto combustion of precursors. The crystal structures of the prepared samples were confirmed by powder XRD technique and particle morphology by FE-SEM. The Photoluminescence properties were investigated under ultraviolet (UV) and vacuum ultraviolet (VUV) radiations respectively. Prepared phosphors were found to have the best luminous performance with respect to intensity and color purity under 254 nm and 147 nm wavelength radiations.

Ingle, J. T.; Sonekar, R. P.; Omanwar, S. K.; Wang, Yuhua; Zhao, Lei

2014-06-01

237

Loop-Free Internet Routing Using Hierarchical Routing Trees  

Microsoft Academic Search

We present a new hierarchical routing algorithmthat combines the loop-free path-finding algorithm(LPA) with the area-based hierarchical routing schemefirst proposed by McQuillan for distance-vector algorithms.The new algorithm, which we call the HierarchicalInformation Path-based Routing (HIPR) algorithm,accommodates an arbitrary number of aggregationlevels and can be viewed as a distributed version ofDijkstra's algorithm running over a hierarchical graph.HIPR is verified to be...

Shree Murthy; J. J. Garcia-luna-aceves

1997-01-01

238

Combustion Synthesis of Magnesium Aluminate  

NASA Astrophysics Data System (ADS)

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.

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

2011-10-01

239

A novel microwave combustion approach for single step synthesis of ?-Al 2O 3 nanopowders  

Microsoft Academic Search

A novel method for synthesis of nano-sized ?-Al2O3 particles in a single step using microwave is being reported for the first time. The sol of aluminum nitrate with urea mixed in the stoichiometric ratios in accordance with jet propellant chemistry, when combusted in a microwave oven gave fine single phase ?-Al2O3 nanoparticles. The resultant oxide powder was characterized by TGA

Kiranmala Laishram; Rekha Mann; Neelam Malhan

240

Synthesis and luminescence properties of nanocrystalline Gd 2O 3:Eu 3+ by combustion process  

Microsoft Academic Search

The nanocrystalline Gd2O3:Eu3+ powders with cubic phase were prepared by a combustion method in the presence of urea and glycol. The effects of the annealing temperature on the crystallization and luminescence properties were studied. The results of XRD show pure phase can be obtained, the average crystallite size could be calculated as 7, 8, 15, and 23nm for the precursor

Yanhong Li; Guangyan Hong

2007-01-01

241

Combustion synthesis and characterization of substituted lithium cobalt oxides in lithium batteries  

Microsoft Academic Search

Substituted lithium cobaltates LiCo0.5M0.5O2 (where M=Ni, Mg, Mn, Zn) have been synthesized by the combustion of mixtures obtained from aqueous solutions containing the respective metal nitrates, LiNO3, and urea in stoichiometric amounts. The mixtures, when dried and fired at 700°C, ignite and yield submicron-sized powders. Physical properties of the synthesized products are discussed in the light of structural (XRD, SEM)

C Julien; M. A Camacho-Lopez; T Mohan; S Chitra; P Kalyani; S Gopukumar

2000-01-01

242

Route 66 Oral Histories  

NSDL National Science Digital Library

The folks at Missouri State University have interviewed a range of business owners along the celebrated Route 66 to tell the amazing story of what life was like living along this American landmark. Visitors can read through interviews with a variety of people, including the long-time owner of the Boots Motel in Carthage, Missouri and Sheldon and Julia Chaney, owner of a popular gas station. It's the type of popular oral history that makes for excellent reading and contemplation. They plan on adding more material in the future, so curious visitors would do well to make return visits to see what's added next.

243

Rotary internal combustion engine  

Microsoft Academic Search

This patent describes an internal combustion rotary engine. It comprises: a housing; a casing mounted in the housing and defining, at least in part, an annular circular piston chamber, a continuous chamber slot formed in the casing and extending the full interior circumference thereof, and a combustion chamber; a shaft mounted in the housing for rotation about its axis and

Bayless

1990-01-01

244

Pressure-gain combustion.  

National Technical Information Service (NTIS)

Pulse combustion has been proposed for gas turbine applications in many early articles and more recently has been demonstrated to produce so-called ''pressure-gain'' in a small gas turbine. The basic concept is that the oscillatory combustion occurs as a ...

G. A. Richards J. Yip R. S. Gemmen M. C. Janus T. Norton

1993-01-01

245

Internal combustion engine  

Microsoft Academic Search

This patent describes an internal combustion engine having a main combustion chamber in a top portion of a piston, and an ignition chamber in a cylinder head, which is provided with a fuel injection valve and an ignition plug, characterized in that the direction in which fuel is ejected from the fuel injection valve is in accordance with the forward

Nagakura

1987-01-01

246

Internal combustion propulsion engine  

Microsoft Academic Search

An internal combustion propulsion engine is described which includes: a spherical engine body having an internal combustion chamber, the engine body being provided with a radially projecting nozzle which has an outwardly divergent conical exhaust opening centrally disposed therein, the nozzle being an extension in the wall of the engine body; a plurality of spaced support struts attached to and

Sing

1988-01-01

247

Coal Combustion Science  

SciTech Connect

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.

Hardesty, D.R. (ed.); Fletcher, T.H.; Hurt, R.H.; Baxter, L.L. (Sandia National Labs., Livermore, CA (United States))

1991-08-01

248

Municipal waste combustion  

SciTech Connect

This book covers the proceedings of the second annual International Specialty Conference on Municipal Waste Combustion. Topics covered include: combustion; refuse derived fuel plants; ash characterization; flue gas cleaning; ash disposal; environmental effects; risk and quality assurance; mercury control; sampling; regulations.

Not Available

1991-01-01

249

Rocket Combustion Chamber Coating  

NASA Technical Reports Server (NTRS)

A coating with the ability to protect (1) the inside wall (i.e., lining) of a rocket engine combustion chamber and (2) parts of other apparatuses that utilize or are exposed to combustive or high temperature environments. The novelty of this invention lies in the manner a protective coating is embedded into the lining.

Holmes, Richard R. (Inventor); McKechnie, Timothy N. (Inventor)

2001-01-01

250

Internal combustion engine with dual combustion chambers  

SciTech Connect

This patent describes a spark-ignition. The overhead valve type internal combustion engine comprises: a cylinder closed at the top by a semi-spherical cylinder head; a piston reciprocating within the cylinder with the piston; cylinder and cylinder head defining at least one combustion chamber; and wherein the cylinder head includes an intake valve aperture, an exhaust valve aperture, and a spark plug aperture; a spark plug within the spark plug aperture; and an intake valve and an exhaust valve mounted for reciprocation within the intake valve aperture and the exhaust valve aperture, respectively, with the valves having heads seated on the apertures and opening towards the piston.

Simay, S.

1987-06-02

251

Japan's microgravity combustion science program  

NASA Technical Reports Server (NTRS)

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.

Sato, Junichi

1993-01-01

252

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

SciTech Connect

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.

Ianos, Robert ['Politehnica' University of Timisoara, Faculty of Industrial Chemistry and Environmental Engineering, P-ta Victoriei No. 2, Timisoara 300006 (Romania)], E-mail: robert_ianos@yahoo.com; Lazau, Ioan; Pacurariu, Cornelia ['Politehnica' University of Timisoara, Faculty of Industrial Chemistry and Environmental Engineering, P-ta Victoriei No. 2, Timisoara 300006 (Romania); Barvinschi, Paul [West University of Timisoara, Faculty of Physics, Bd. V. Parvan No. 4, Timisoara 300223 (Romania)

2009-07-15

253

Intelligent route surveillance  

NASA Astrophysics Data System (ADS)

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.

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

2009-05-01

254

A General Vehicle Routing Problem  

Microsoft Academic Search

In this paper, we study a rich vehicle routing problem incorporating various complexities found in real-life applications. The General Vehicle Routing Problem (GVRP) is a combined load acceptance and generalised vehicle routing problem. Among the real-life requirements are time window restrictions, a heterogeneous vehicle fleet with different travel times, travel costs and capacity, multi-dimensional capacity constraints, order\\/vehicle compatibility constraints, orders

Asvin Goel; Volker Gruhn

2008-01-01

255

Energy Minimizing Vehicle Routing Problem  

Microsoft Academic Search

This paper proposes a new cost function based on distance and load of the vehicle for the Capacitated Vehicle Routing Problem.\\u000a The vehicle-routing problem with this new load-based cost objective is called the Energy Minimizing Vehicle Routing Problem\\u000a (EMVRP). Integer linear programming formulations with O(n\\u000a 2) binary variables and O(n\\u000a 2) constraints are developed for the collection and delivery cases,

Imdat Kara; Bahar Yetis Kara; M. Kadri Yetis

2007-01-01

256

Access Routes for Nutritional Therapy  

Microsoft Academic Search

Enteral nutrition (EN) and total\\u000a parenteral nutrition (TPN) may provide life-sustaining therapy for\\u000a surgical patients. The duration of nutritional therapy (enteral or\\u000a parenteral) implies distinct access routes. We review the main aspects\\u000a related to access routes for nutrient delivery. The enteral route,\\u000a whenever feasible, is preferred. For EN lasting less than 6 weeks,\\u000a nasoenteric tubes are the route of choice.

2000-01-01

257

Ocean urea fertilization for carbon credits poses high ecological risks.  

PubMed

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

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

258

Laser Applications in Combustion and Combustion Diagnostics  

Microsoft Academic Search

Lasers have become one of the most widely used tools in the scientific community, particularly in the field of combustion. Since the laser is a nonintrusive source of high-intensity energy that can be precisely controlled, it can be used as an ignition source in applications such as solid or liquid rockets, supersonic jet engines, and space-based microgravity experiments. Furthermore, due

Larry C. Liou

1993-01-01

259

Internal combustion engine with multiple combustion chambers  

Microsoft Academic Search

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

Gruenwald

1992-01-01

260

SUPPLEMENTAL VALUE OF FEED GRADE BIURET AND UREA-MOLASSES FOR COWS ON DRY WINTER GRASS l ,2  

Microsoft Academic Search

SUMMARY Four trials were conducted to evaluate the supplemental value of feed grade biuret (in dry supplements) and urea (in liquid urea-molasses mixtures) when compared to natural protein and urea in dry supplements for beef cows grazing low quality dry winter range grass. Urea or feed grade biuret provided 50% of the nitrogen in 30% CP dry supplements and urea

Ivan G. Rush; Robert Totusek

261

Multipath Routing Metrics for Reliable Wireless Mesh Routing Topologies  

Microsoft Academic Search

Several emerging classes of applications that run over wireless networks have a need for mathematical models and tools to systematically characterize the reliability of the network. We propose two metrics for measuring the reliability of wireless mesh routing topologies, one for flooding and one for unicast routing. The Flooding Path Probability (FPP) metric measures the end-to-end packet delivery probability when

Phoebus Chen; Karl Henrik Johansson; Paul Balister; Béla Bollobás; Shankar Sastry

2011-01-01

262

Loop-Free Internet Routing Using Hierarchical Routing Trees.  

National Technical Information Service (NTIS)

The authors present a new hierarchical routing algorithm that combines the loop-free path-finding algorithm (LPA) with the area-based hierarchical routing scheme first proposed by McQuillan for distance-vector algorithms. The new algorithm, which they cal...

J. J. Garcia-Luna-Aceves S. Murthy

1997-01-01

263

Catalytic combustion of dilute acetone over Cu-doped ceria catalysts  

Microsoft Academic Search

CuxCe1?xOy (x=0.06, 0.13, and 0.23) were prepared by a solution combustion route using glycine as the fuel and tested for the catalytic combustion of dilute acetone in air. The structural characteristics of the catalysts were investigated by specific surface area, X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and temperature-programmed reduction (TPR) techniques. The results reveal that

Chaoquan Hu; Qingshan Zhu; Zheng Jiang; Lin Chen; Rongfang Wu

2009-01-01

264

Microwave-assisted combustion synthesis of nanocrystalline MgAl 2O 4 spinel powder  

Microsoft Academic Search

A stoichiometric MgAl2O4 spinel powder was synthesized by a microwave-assisted combustion synthesis (MWCS) route. For the purpose of comparison, another stoichiometric MgAl2O4 spinel powder was also prepared following the conventional combustion synthesis (CCS) method. The batch size had a strong influence on the specific surface area of the material, which in turn is highly dependent on the preparation method adopted.

I. Ganesh; R. Johnson; G. V. N. Rao; Y. R. Mahajan; S. S. Madavendra; B. M. Reddy

2005-01-01

265

DEVELOPMENT OF ACTIVATED CARBONS FROM COAL COMBUSTION BY-PRODUCTS  

Microsoft Academic Search

The increasing role of coal as a source of energy in the 21st century will demand environmental and cost-effective strategies for the use of coal combustion by-products (CCBPs), mainly unburned carbon in fly ash. Unburned carbon is nowadays regarded as a waste product and its fate is mainly disposal, due to the present lack of efficient routes for its utilization.

Harold H. Schobert; M. Mercedes Maroto-Valer; Zhe Lu

2003-01-01

266

Effect of sodium chloride intake on urine volume, urinary urea excretion, and milk urea concentration in lactating dairy cattle.  

PubMed

Milk urea nitrogen (MUN; mg of N/dL) has been shown to be related to excretion of urinary urea N (UUN; g of N/d) and total excretion of urinary N (UN; g of N/d) in dairy cows. In the present experiment, it was hypothesized that MUN and the relationship between MUN and UUN or UN is affected by urine volume as a result of dietary sodium chloride intake. Twelve lactating Holstein-Friesian dairy cows (mean ± SD: milk production 28.1±3.23 kg/d and 190±41 d in milk), of which 4 were fitted with catheters in the urine bladder and jugular vein, were randomly assigned to 4 dietary levels of sodium chloride (3, 9, 14, and 19 g of Na/kg of DM) according to a triple 4×4 Latin square design. Cows were fed at 95% of ad libitum intake, excluding salt addition. Milk was analyzed for MUN and protein content; urine was analyzed for total N, urea, and creatinine content; feces were analyzed for total N and DM content; and blood plasma was analyzed for urea and creatinine content. Creatinine clearance rate (CCR; L/min) and renal urea reabsorption ratio were estimated based on plasma concentrations of urea and creatinine, and total excretion of urea and creatinine in urine. Intake of DM and N, milk production, and milk protein content were (mean ± SD), on average, 21.4±1.24 kg/d, 522±32.0 g/d, 25.4±2.53 kg/d, and 3.64±0.186%, respectively. A linear relationship was found between Na intake and urine production [urine (kg/d; mean ± SE)=7.5±4.33+0.136±0.0143 × Na intake (g/d)] and between Na intake and MUN [MUN (mg/dL; mean ± SE)=13.5±0.35-0.0068±0.00104 × Na intake (g/d)]. Despite the decrease in MUN with increased Na intake, UN excretion increased linearly with Na intake. Excretion of UUN was not affected by dietary Na content. A linear plateau relationship was observed between CCR and renal urea reabsorption. An increase in CCR coincided with an increase in calculated renal urea reabsorption until a CCR breakpoint value (mean ± SD) of 1.56±0.063 L/min was reached. We conclude that Na intake is negatively related to MUN, whereas UUN is not affected. Variation in mineral intake levels that affect urine volume should, therefore, be taken into account when using MUN as an indicator of UUN in dairy cattle. PMID:23063155

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

2012-12-01

267

Combustion in supersonic flow  

NASA Technical Reports Server (NTRS)

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.

Northam, G. B.

1985-01-01

268

Gas turbine combustion instability  

SciTech Connect

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.

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

1996-09-01

269

Sandia Combustion Research: Technical review  

SciTech Connect

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.

NONE

1995-07-01

270

Role for urea in nitrification by polar marine Archaea  

PubMed Central

Despite the high abundance of Archaea in the global ocean, their metabolism and biogeochemical roles remain largely unresolved. We investigated the population dynamics and metabolic activity of Thaumarchaeota in polar environments, where these microorganisms are particularly abundant and exhibit seasonal growth. Thaumarchaeota were more abundant in deep Arctic and Antarctic waters and grew throughout the winter at surface and deeper Arctic halocline waters. However, in situ single-cell activity measurements revealed a low activity of this group in the uptake of both leucine and bicarbonate (<5% Thaumarchaeota cells active), which is inconsistent with known heterotrophic and autotrophic thaumarchaeal lifestyles. These results suggested the existence of alternative sources of carbon and energy. Our analysis of an environmental metagenome from the Arctic winter revealed that Thaumarchaeota had pathways for ammonia oxidation and, unexpectedly, an abundance of genes involved in urea transport and degradation. Quantitative PCR analysis confirmed that most polar Thaumarchaeota had the potential to oxidize ammonia, and a large fraction of them had urease genes, enabling the use of urea to fuel nitrification. Thaumarchaeota from Arctic deep waters had a higher abundance of urease genes than those near the surface suggesting genetic differences between closely related archaeal populations. In situ measurements of urea uptake and concentration in Arctic waters showed that small-sized prokaryotes incorporated the carbon from urea, and the availability of urea was often higher than that of ammonium. Therefore, the degradation of urea may be a relevant pathway for Thaumarchaeota and other microorganisms exposed to the low-energy conditions of dark polar waters.

Alonso-Saez, Laura; Waller, Alison S.; Mende, Daniel R.; Bakker, Kevin; Farnelid, Hanna; Yager, Patricia L.; Lovejoy, Connie; Tremblay, Jean-Eric; Potvin, Marianne; Heinrich, Friederike; Estrada, Marta; Riemann, Lasse; Bork, Peer; Pedros-Alio, Carlos; Bertilsson, Stefan

2012-01-01

271

Role for urea in nitrification by polar marine Archaea.  

PubMed

Despite the high abundance of Archaea in the global ocean, their metabolism and biogeochemical roles remain largely unresolved. We investigated the population dynamics and metabolic activity of Thaumarchaeota in polar environments, where these microorganisms are particularly abundant and exhibit seasonal growth. Thaumarchaeota were more abundant in deep Arctic and Antarctic waters and grew throughout the winter at surface and deeper Arctic halocline waters. However, in situ single-cell activity measurements revealed a low activity of this group in the uptake of both leucine and bicarbonate (<5% Thaumarchaeota cells active), which is inconsistent with known heterotrophic and autotrophic thaumarchaeal lifestyles. These results suggested the existence of alternative sources of carbon and energy. Our analysis of an environmental metagenome from the Arctic winter revealed that Thaumarchaeota had pathways for ammonia oxidation and, unexpectedly, an abundance of genes involved in urea transport and degradation. Quantitative PCR analysis confirmed that most polar Thaumarchaeota had the potential to oxidize ammonia, and a large fraction of them had urease genes, enabling the use of urea to fuel nitrification. Thaumarchaeota from Arctic deep waters had a higher abundance of urease genes than those near the surface suggesting genetic differences between closely related archaeal populations. In situ measurements of urea uptake and concentration in Arctic waters showed that small-sized prokaryotes incorporated the carbon from urea, and the availability of urea was often higher than that of ammonium. Therefore, the degradation of urea may be a relevant pathway for Thaumarchaeota and other microorganisms exposed to the low-energy conditions of dark polar waters. PMID:23027926

Alonso-Sáez, Laura; Waller, Alison S; Mende, Daniel R; Bakker, Kevin; Farnelid, Hanna; Yager, Patricia L; Lovejoy, Connie; Tremblay, Jean-Éric; Potvin, Marianne; Heinrich, Friederike; Estrada, Marta; Riemann, Lasse; Bork, Peer; Pedrós-Alió, Carlos; Bertilsson, Stefan

2012-10-30

272

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

PubMed

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

Zarzyka, Iwona

2014-01-01

273

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

PubMed Central

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.

2014-01-01

274

Anonymous connections and onion routing  

Microsoft Academic Search

Onion routing is an infrastructure for private communication over a public network. It provides anonymous connections that are strongly resistant to both eavesdropping and traffic analysis. Onion routing's anonymous connections are bidirectional, near real-time, and can be used anywhere a socket connection can be used. Any identifying information must be in the data stream carried over an anonymous connection. An

Michael G. Reed; Paul F. Syverson; David M. Goldschlag

1998-01-01

275

Route Optimization Security Design Protocol  

Microsoft Academic Search

Unlike Mobile IPv4, where mobile node communicates with its peer through a longer path, via Home Agent, in Mobile IPv6 a mobile node directly communicates with its peers even though it moves to the new location and changes its IP address, this mechanism is called Route Optimization. In Route Optimization, the mobile node sends the binding message to its peer

Muhammad Taqi; Syed Rehan Afzal; Hamid Mukhtar; Seung-wha Yoo; Dong-Kyu Kim; Ki-Hyung Kim

276

Origins of Internet Routing Instability  

Microsoft Academic Search

This paper examines the network routing messages ex- changed between core Internet backbone routers. Internet routing in- stability, or the rapid fluctuation of network reachability information, is an important problem currently facing the Internet engineering commu- nity. High levels of network instability can lead to packet loss, increased network latency and time to convergence. At the extreme, high levels of

Craig Labovitz; G. Robert Malan; Farnam Jahanian

1999-01-01

277

A Failsafe Distributed Routing Protocol  

Microsoft Academic Search

An algorithm for constructing and adaptively maintaining routing tables in communication networks is presented. The algorithm can be employed in message as well as circuit switching networks, uses distributed computation, provides routing tables that are loop-free for each destination at all times, adapts to changes in network flows, and is completely failsafe. The latter means that after arbitrary failures and

PHILIP M. MERLIN; ADRIAN SEGALL

1979-01-01

278

Modelling Routes towards Learning Goals  

ERIC Educational Resources Information Center

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…

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

2006-01-01

279

Simulation and experimental study of intercalation of urea in kaolinite.  

PubMed

Experimental measurements and molecular simulations were used to describe the characteristics of the kaolinite/urea intercalation compound. The intercalation compound was synthesized by a mechanochemical method and examined by X-ray diffraction and thermogravimetry. Additionally, a series of NpT (constant particle number-pressure-temperature) simulations was performed to identify thermodynamically stable basal spacings. From the simulations the most probable molecular orientations were determined for single and double layered arrangements of urea molecules that develop between the layers of kaolinite. PMID:19386317

Rutkai, Gábor; Makó, Eva; Kristóf, Tamás

2009-06-01

280

Bis(acetato-?O)bis-(thio-urea-?S)cobalt(II)  

PubMed Central

The title compound, [Co(CH3COO)2(CH4N2S)2], is isotypic with the corresponding ZnII complex. The metal atom is in a distorted tetra­hedral coordination environment with the two S atoms from two thio­urea ligands and two O atoms from two acetate anions as the coordinating atoms. All H atoms of the thio­urea ligands are involved in N—H?O and N—H?S hydrogen bonds, leading to a three-dimensional network.

Lutz, Martin

2014-01-01

281

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

PubMed Central

The title compound, [Pr(H2O)9]I3·2CS(NH2)2, an adduct of nona­aqua­praseodymium triiodide with two thio­urea mol­ecules, is composed from [Pr(H2O)9]3+ cations (polyhedron: monocapped tetra­gonal anti­prism), noncoordinated thio­urea mol­ecules 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.

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

2012-01-01

282

Studies in premixed combustion  

SciTech Connect

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)

Sivashinsky, G.I.

1992-01-01

283

Gas turbine combustion instability.  

National Technical Information Service (NTIS)

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 ...

G. A. Richards G. T. Lee

1996-01-01

284

High Mach Number Combustion.  

National Technical Information Service (NTIS)

Recent developments in the mathematical theory of high Mach number combustion are presented. The phenomena in this regime are enormously complex and the mechanisms responsible for the variety of physical phenomena are poorly understood. The current advanc...

A. Majda

1986-01-01

285

Dynamic effects of combustion  

NASA Technical Reports Server (NTRS)

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.

Oppenheim, A. K.

1982-01-01

286

Combustion Stability Rating Techniques.  

National Technical Information Service (NTIS)

The objectives of a comprehensive investigation of three techniques for rating the combustion stability of liquid-propellant rocket engines were the establishment of the characteristics of the techniques and of their intercorrelations. The techniques stud...

L. P. Combs F. W. Hoehn S. R. Webb E. E. Lockwood D. T. Campbell

1966-01-01

287

Combustion Technology Outreach  

NASA Technical Reports Server (NTRS)

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.

1995-01-01

288

Combustion and Propulsion.  

National Technical Information Service (NTIS)

A brief review of combustion and propulsion research currently underway at the Institute for Aerospace Studies is provided. Afterburning rocket exhaust plume properties are being investigated both experimentally and by mathematical analysis. The objective...

J. P. Sislian Y. Sheng L. Jiang R. A. Cusworth J. T. C. Hu

1989-01-01

289

Combustion and Emissions  

NSDL National Science Digital Library

A flickering candle lights the way for a scientific investigation. This lesson uses hands-on demonstrations and web-based presentations to explore the science of combustion. Students become environmental experts as they learn about combustion emissions and how they affect human health and the environment. The lesson would be useful for physics and chemistry for grades 7-12 and would take multiple class periods to cover in full.

2013-07-01

290

Coal slurry combustion  

Microsoft Academic Search

Experimental and numerical results are presented from examining the combustion of coal-slurry fuels. The combustion characteristics of a coal slurry agglomeration with and without metallic additives were investigated. The kinetics of the C-COâ reaction was re-examined since it has a significant influence upon the burning of the droplets. The inclusion of metallic additives influences the mass reduction rate in the

1984-01-01

291

75 FR 40827 - Petitions Concerning Whether Ammonia or Urea Sold or Distributed and Used for Certain Purposes...  

Federal Register 2010, 2011, 2012, 2013

...Petitions Concerning Whether Ammonia or Urea Sold or Distributed and Used for Certain...petitions concerning whether ammonia or urea sold or distributed and used for certain...petitions concerning whether ammonia or urea sold or distributed and used for...

2010-07-14

292

Ad-Hoc Routing Protocol Avoiding Route Breaks Based on AODV  

Microsoft Academic Search

Many routing protocols in mobile ad-hoc networks have been developed by many researchers. One of ad-hoc routing protocol types is the on-demand routing that establishes a route to a destination node only when required. But it is necessary to re-establish a new route when its route breaks down. However, most of on-demand routing protocols re-establish a new route after a

Masayuki Tauchi; Tetsuo Ideguchi; Takashi Okuda

2005-01-01

293

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

PubMed

Dietary protein and salt affect the concentration of milk urea nitrogen (MUN; mg of N/dL) and the relationship between MUN and excretion of urea nitrogen in urine (UUN; g of N/d) of dairy cattle. The aim of the present study was to examine the effects of dietary protein and sodium chloride (NaCl) intake separately, and their interaction, on MUN and UUN, on the relationship between UUN and MUN, on renal recycling of urea, and on urea transfer to the gastrointestinal tract. Twelve second-parity cows (body weight of 645±37 kg, 146±29 d in milk, and a milk production of 34.0±3.28 kg/d), of which 8 were previously fitted with a rumen cannula, were fitted with catheters in the urine bladder and jugular vein. The experiment had a split-plot arrangement with dietary crude protein (CP) content as the main plot factor [116 and 154 g of CP/kg of dry matter (DM)] and dietary NaCl content as the subplot factor (3.1 and 13.5 g of Na/kg of DM). Cows were fed at 95% of the average ad libitum feed intake of cows receiving the low protein diets. Average MUN and UUN were, respectively, 3.90 mg of N/dL and 45 g of N/d higher for the high protein diets compared with the low protein diets. Compared with the low NaCl diets, MUN was, on average, 1.74 mg of N/dL lower for the high NaCl diets, whereas UUN was unaffected. We found no interaction between dietary content of protein and NaCl on performance characteristics or on MUN, UUN, urine production, and renal clearance characteristics. The creatinine clearance rate was not affected by dietary content of protein and NaCl. Urea transfer to the gastrointestinal tract, expressed as a fraction of plasma urea entry rate, was negatively related to dietary protein, whereas it was not affected by dietary NaCl content. We found no interaction between dietary protein and NaCl content on plasma urea entry rate and gastrointestinal urea entry rate or their ratio. The relationship between MUN and UUN was significantly affected by the class variable dietary NaCl content: UUN=-17.7±7.24 + 10.09±1.016 × MUN + 2.26±0.729 × MUN (for high NaCl); R(2)=0.85. Removal of the MUN × NaCl interaction term lowered the coefficient of determination from 0.85 to 0.77. In conclusion, dietary protein content is positively related to MUN and UUN, whereas dietary NaCl content is negatively correlated to MUN but NaCl content is not related to UUN. We found no interaction between dietary protein and NaCl content on performance, MUN, UUN, or renal urea recycling, nor on plasma urea entry rate and urea transfer to the gastrointestinal tract. For a proper interpretation of the relationship between MUN and UUN, the effect of dietary NaCl should be taken into account, but we found no evidence that the effect of dietary NaCl on MUN is dependent on dietary protein content. PMID:23871366

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

2013-09-01

294

METC Combustion Research Facility  

SciTech Connect

The objective of the Morgantown Energy Technology Center (METC) high pressure combustion facility is to provide a mid-scale facility for combustion and cleanup research to support DOE`s advanced gas turbine, pressurized, fluidized-bed combustion, and hot gas cleanup programs. The facility is intended to fill a gap between lab scale facilities typical of universities and large scale combustion/turbine test facilities typical of turbine manufacturers. The facility is now available to industry and university partners through cooperative programs with METC. High pressure combustion research is also important to other DOE programs. Integrated gasification combined cycle (IGCC) systems and second-generation, pressurized, fluidized-bed combustion (PFBC) systems use gas turbines/electric generators as primary power generators. The turbine combustors play an important role in achieving high efficiency and low emissions in these novel systems. These systems use a coal-derived fuel gas as fuel for the turbine combustor. The METC facility is designed to support coal fuel gas-fired combustors as well as the natural gas fired combustor used in the advanced turbine program.

Halow, J.S.; Maloney, D.J.; Richards, G.A.

1993-11-01

295

Pseudoshock combustion regime  

SciTech Connect

The combustion of fuels flowing with supersonic velocity in a duct of constant cross section is analyzed. Experimental data on the pressure at the duct wall are used to calculate the heat-release rates by a one-dimensional procedure that takes into account the specific characteristics of combustion in a pseudoshock. It is shown that the heat-release rate, averaged over the length of the combustion zone and normalized to the maximum possible rate, depends on the ratio of the length of the combustion zone to the pseudoshock length for the isothermal case in flow stagnation up to a Mach number M = 1.0 and not on the fuel injection technique or the length of the duct. An approach is suggested for determining the duct geometry in the pseudoshock combustion regime so as to organize the combustion process efficiently as a function of the flow parameters and the physicochemical characteristics of the field, which can be determined from specially designed experiments.

Tret`yakov, P.K. [Institute of Theoretical and Applied Mechanics, Novosibirsk (Russian Federation)

1994-05-01

296

Coal combustion system  

DOEpatents

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.

Wilkes, Colin (Lebanon, IN); Mongia, Hukam C. (Carmel, IN); Tramm, Peter C. (Indianapolis, IN)

1988-01-01

297

Legislative Route 16034, Section 2 and Legislative Route 409, Section 7, Pennsylvania Route 66, Pennsylvania.  

National Technical Information Service (NTIS)

The proposed project consists of the construction of 2.7 miles of highway, approximately half of which will be limited access, on new location parallel to existing Legislative Route 16034 and Legislative Route 409, together comprising a portion of Pennsyl...

1973-01-01

298

46 CFR 45.175 - Applicable routes.  

Code of Federal Regulations, 2013 CFR

...HOMELAND SECURITY (CONTINUED) LOAD LINES GREAT LAKES LOAD LINES Unmanned River Barges on Lake Michigan Routes § 45.175 Applicable routes...following routes, including intermediate ports, on Lake Michigan, between Calumet Harbor, IL,...

2013-10-01

299

46 CFR 45.175 - Applicable routes.  

Code of Federal Regulations, 2010 CFR

...SECURITY (CONTINUED) LOAD LINES GREAT LAKES LOAD LINES Unmanned River Barges on Lake Michigan Routes § 45.175 Applicable routes...subpart applies to the following routes on Lake Michigan, between Chicago (Calumet Harbor),...

2010-10-01

300

46 CFR 45.175 - Applicable routes.  

Code of Federal Regulations, 2012 CFR

...SECURITY (CONTINUED) LOAD LINES GREAT LAKES LOAD LINES Unmanned River Barges on Lake Michigan Routes § 45.175 Applicable routes...routes, including intermediate ports, on Lake Michigan, between Calumet Harbor, IL, and—...

2012-10-01

301

46 CFR 45.175 - Applicable routes.  

Code of Federal Regulations, 2011 CFR

...SECURITY (CONTINUED) LOAD LINES GREAT LAKES LOAD LINES Unmanned River Barges on Lake Michigan Routes § 45.175 Applicable routes...routes, including intermediate ports, on Lake Michigan, between Calumet Harbor, IL, and—...

2011-10-01

302

Oligomeric Structure and Functional Characterization of the Urea Transporter from Actinobacillus pleuropneunomiae  

PubMed Central

Urea transporters facilitate urea permeation across cell membranes in prokaryotes and eukaryotes. Bacteria use urea either as a means to survive in acidic environments and/or as a nitrogen source. The urea transporter ApUT from Actinobacillus pleuropneumoniae, the pathogen that causes porcine pleurisy and pneumonia, was expressed in E. coli and purified. Analysis of the recombinant protein using cross-linking and blue-native gel electrophoresis established that ApUT is a dimer in detergent solution. To determine the urea transport kinetics of ApUT, purified protein was reconstituted into proteoliposomes, and urea efflux was measured by stopped-flow fluorometry. The measured urea flux was saturable, could be inhibited by phloretin, and was not affected by pH. Two-dimensional crystals of the biologically active ApUT show that it is also dimeric in a lipid membrane and provide the first structural information on a member of the urea transporter family.

Raunser, Stefan; Mathai, John C.; Abeyrathne, Priyanka D.; Rice, Amanda J.; Zeidel, Mark L.; Walz, Thomas

2009-01-01

303

Protein stabilization and counteraction of denaturing effect of urea by glycine betaine.  

PubMed

The counteraction of the denaturing effect of urea by osmolytes has been one of the most studied problems of osmolyte action. However, the possibility of synergy in osmolyte mixtures has often been neglected. Here, we report synergy in the glycine betaine (GB)-urea mixture by using a model peptide. The results show that in the GB-urea mixture, GB acts as a stronger osmolyte and urea becomes a weaker denaturing agent. This is reflected by an increase in the exclusion of GB from the peptide surface and a decrease in interactions between the peptide and urea. The cause of this synergistic behaviour includes direct interactions between GB and urea through hydrogen bonding, van der Waals interactions between them and strengthening of hydrogen bonding network of water in the GB-urea mixture. The results obtained in this study provide insights into osmolyte induced counteraction of the denaturing effect of urea. PMID:24698949

Kumar, Narendra; Kishore, Nand

2014-05-01

304

Reactions of Urea, Semicarbazide and Carbazide Reaktionen von Harnstoff, Semicarbazid und Carbohydrazid.  

National Technical Information Service (NTIS)

Reaction products of urea, semicarbazide and carbazide, with their respective acid salts, were investigated in melts by differential thermal analysis and in aqueous solution. Urea hydrochloride in melts yields biuret and an amount of hydrocyanic acid, inc...

W. Engel

1973-01-01

305

One-pot and one-step synthesis of bioactive urease/ZnFe2O4 nanocomposites and their application in detection of urea.  

PubMed

This communication describes a novel environmentally friendly method to prepare bioactive urease/ZnFe2O4 nanocomposites through a one-pot and one-step process. The synthetic procedure is triggered through a biological mineralization process of decomposition of urea catalyzed by urease. During the growth of ZnFe2O4, urease molecules are immobilized by original ZnFe2O4 nanoparticles. As a consequence, the bioactive urease/ZnFe2O4 nanoparticle composites are assembled. This simple route is expected to endow the bioactive nanocomposites with new properties for various interesting fields. PMID:24819691

Shi, Haitang; Chen, Xue; Li, Linlin; Tan, Longfei; Ren, Xiangling; Ren, Jun; Meng, Xianwei

2014-05-28

306

Route visualization using detail lenses.  

PubMed

We present a method designed to address some limitations of typical route map displays of driving directions. The main goal of our system is to generate a printable version of a route map that shows the overview and detail views of the route within a single, consistent visual frame. Our proposed visualization provides a more intuitive spatial context than a simple list of turns. We present a novel multifocus technique to achieve this goal, where the foci are defined by points of interest (POI) along the route. A detail lens that encapsulates the POI at a finer geospatial scale is created for each focus. The lenses are laid out on the map to avoid occlusion with the route and each other, and to optimally utilize the free space around the route. We define a set of layout metrics to evaluate the quality of a lens layout for a given route map visualization. We compare standard lens layout methods to our proposed method and demonstrate the effectiveness of our method in generating aesthetically pleasing layouts. Finally, we perform a user study to evaluate the effectiveness of our layout choices. PMID:20075484

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

2010-01-01

307

Past Tense Route Priming  

PubMed Central

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. 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.

Cohen-Shikora, Emily R.; Balota, David A.

2013-01-01

308

Past tense route priming.  

PubMed

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

Cohen-Shikora, Emily R; Balota, David A

2013-03-01

309

Distributed roadmap aided routing in sensor networks  

Microsoft Academic Search

Communication between arbitrary pairs of nodes has become critical to support in emerging sensor networking applications. Traditional routing techniques for multi-hop wireless networks either require high control overhead in computing and maintaining routes, or may lead to unbounded route-stretch. In order to bound the route-stretch, we propose a distributed shortest-path roadmap based routing paradigm that embodies two ideas: routing hole

Zizhan Zheng; Kai-Wei Fan; Prasun Sinha; Yusu Wang

2008-01-01

310

A general heuristic for vehicle routing problems  

Microsoft Academic Search

We present a unified heuristic which is able to solve five different variants of the vehicle routing problem: the vehicle routing problem with time windows (VRPTW), the capacitated vehicle routing problem (CVRP), the multi-depot vehicle routing problem (MDVRP), the site-dependent vehicle routing problem (SDVRP) and the open vehicle routing problem (OVRP).All problem variants are transformed into a rich pickup and

David Pisinger; Stefan Ropke

2007-01-01

311

Tailoring of analytical performances of urea biosensors using nanomaterials  

NASA Astrophysics Data System (ADS)

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.

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

2013-03-01

312

Ammonia Production from Solid Urea Using Non-Thermal Plasma  

Microsoft Academic Search

Among various NOx reduction technologies, selective catalytic reduction (SCR) methods have been studied for cleaning of diesel engine exhaust. Urea SCR system, in which ammonia is used as reducing agent is thought to be one of the most promising methods. However, further improvement of the performance is required at low temperatures for example below 400 K. The purpose of this

Yoshihiro Iitsuka; Hiroki Yamauchi; Graciela Prieto; Kazunori Takashima; Akira Mizuno

2007-01-01

313

Anion recognition by hydrogen bonding: urea-based receptors.  

PubMed

Since 1992 a variety of urea-based anion receptors have been synthesised, of varying complexity and sophistication. This critical review will focus on some distinctive aspects of anion recognition by urea derivatives, with a special reference to: (i) design and synthesis, (ii) methodologies for the investigation of the receptor-anion interaction in solution, (iii) the interpretation of the solution behaviour on the basis of the structural interplay between the receptor and the anion. It will be shown that the efficiency of urea as a receptor subunit depends on the presence of two proximate polarised N-H fragments, capable (i) of chelating a spherical anion or (ii) of donating two parallel H-bonds to the oxygen atoms of a carboxylate or of an inorganic oxoanion, a property which is shared with other diamides, e.g. squaramide. The wide use of urea in the design of neutral anion receptors seems to depends on the ease of its synthesis, in particular through the reaction of a primary amine group with an isocyanate, which allows the high-yield preparation of symmetrically and unsymmetrically substituted derivatives (83 references). PMID:20818452

Amendola, Valeria; Fabbrizzi, Luigi; Mosca, Lorenzo

2010-10-01

314

Pt nanoflower/polyaniline composite nanofibers based urea biosensor.  

PubMed

Hybrid materials with special structures are of great interest because of their superior properties compared with their pure counterparts. Hybrid polyaniline (PANi) nanofibers with integrated Pt nanoflowers are studied in this research. PANi is prepared by in situ polymerization of aniline on an electrospun nanofiber template in an acidic solution with ammonium persulfate (APS) as the oxidant. Pt nanoflowers are further electrodeposited onto the PANi nanofibers backbone by cyclic voltammetry (CV), resulting in novel functionalized hybrid nanofibers. The coverage of Pt nanoflowers on PANi nanofibers can be facilely controlled by adjusting the electrodeposition conditions. The factors affecting Pt nanoflowers formation are further investigated. As a demonstration, urease is immobilized onto the Pt/PANi hybrid nanofibers and the composite was employed as the sensing platform for urea detection in a flow-injection-analysis (FIA) system. The detection of urea shows a wide linear range (up to 20 mM), a good limit of detection of 10 ?M (S/N=3), and an excellent anti-interference property against chloride ion. In addition, it was found that the response to urea was attributed not only to the conductivity change of PANi due to the interaction between PANi and ammonia (liberated from the enzymatic reaction), but also to the interaction between Pt nanoflowers and amine groups in urea. The strategy developed in this study can be extended to synthesize other composite nanofibers consisting of conducting polymer and metal nanoparticles for a wide range of sensing applications. PMID:21986562

Jia, Wenzhao; Su, Liang; Lei, Yu

2011-12-15

315

Obtaining granular NPK fertilizers from single superphosphate and urea  

Microsoft Academic Search

A laboratory study was conducted to elaborate methods for obtaining granular NPK fertilizers from mixtures of single superphosphate (SSP) with urea and potassium salts. Samples of products of various grades containing 32–39% fertilizer nutrients and some micronutrients (B, Cu, Co, Mo, Mn) were obtained and their characteristics determined. Instead of cured SSP the usage of a fresh den product was

E. Aasamäe; E. Arumeel; M. Einard; M. Veiderma

1993-01-01

316

Mechanosynthesis of pharmaceutically relevant sulfonyl-(thio)ureas.  

PubMed

We demonstrate the first application of mechanochemistry to conduct the synthesis of sulfonyl-(thio)ureas, including known anti-diabetic drugs tolbutamide, chlorpropamide and glibenclamide, in good to excellent isolated yields by either stoichiometric base-assisted or copper-catalysed coupling of sulfonamides and iso(thio)cyanates. PMID:24256886

Tan, Davin; Strukil, Vjekoslav; Mottillo, Cristina; Friš?i?, Tomislav

2014-05-25

317

A RAPID AND PRECISE METHOD FOR THE DETERMINATION OF UREA  

Microsoft Academic Search

A method is described for the determination of urea in plasma and urine. The effects of variations in the experimental conditions are examined and the results of recovery experiments and other tests of precision and accuracy are reported.In comparison with other methods in current use, this method has distinct advantages in sensitivity, simplicity, and precision, thus economizing in time, sample

J. K. Fawcett; J. E. Scott

1960-01-01

318

Urea as a Protein Replacement for Ruminants: A Review  

Microsoft Academic Search

It has been recognized for some time that urea (and other nonprotein nitro- gen-containing compounds) may be used to replace a portion of the protein in the rations of ruminant animals (28, 104). The mechanism making this pos- sible appears to be one in which proteins are synthesized from simple nitrogenous substances by the growth and multiplication of the bacteria

J. T. Reid

1953-01-01

319

Use of Two Sulfonyl Urea Herbicides in Lowbush Blueberry  

Microsoft Academic Search

The continuous use of the broad spectrum herbicide hexazinone since 1981 has resulted in many changes to the weedy flora of lowbush blueberry fields, including shifts to hexazinone-tolerant species. Many of these occur in patches and could best be controlled by selective, foliar herbicide treatments. Preliminary assessments of several sufonyl urea (SU) herbicides indicated that tribenuron (Spartan or Express 75%

Klaus I. N. Jensen; Eric G. Specht

2004-01-01

320

New urea-absorbing polymers for artificial kidney machines  

NASA Technical Reports Server (NTRS)

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.

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

1975-01-01

321

Suitable potentiometric enzyme sensors for urea and creatinine.  

PubMed

Enzyme sensors for urea and creatinine were developed by coupling an ammonia gas-diffusion electrode with triacetate cellulose membranes entrapping urease or creatinine deiminase enzymes. Satisfactory results were obtained by using these sensors both in standard solutions and in authentic biological matrices. PMID:2393088

Campanella, L; Sammartino, M P; Tomassetti, M

1990-06-01

322

Crystal Engineering with Urea and Thiourea Hydrogen-Bonding Groups  

SciTech Connect

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.

Custelcean, Radu [ORNL

2008-01-01

323

Escalating Worldwide use of Urea – A Global Change Contributing to Coastal Eutrophication  

Microsoft Academic Search

While the global increase in the use of nitrogen-based fertilizers has been well recognized, another change in fertilizer\\u000a usage has simultaneously occurred: a shift toward urea-based products. Worldwide use of urea has increased more than 100-fold\\u000a in the past 4 decades and now constitutes >50% of global nitrogenous fertilizer usage. Global urea usage extends beyond agricultural\\u000a applications; urea is also

Patricia M. Glibert; John Harrison; Cynthia Heil; Sybil Seitzinger

2006-01-01

324

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

Microsoft Academic Search

The urease was immobilized onto nanoporous alumina membranes prepared by the two-step anodization method, and a novel piezoelectric urea sensing system with separated porous alumina\\/urease electrode has been developed through measuring the conductivity change of immobilized urease\\/urea reaction. The process of urease immobilization was optimized and the performance of the developed urea biosensor was evaluated. The obtained urea biosensor presented

Zhengpeng Yang; Shihui Si; Hongjuan Dai; Chunjing Zhang

2007-01-01

325

Curing of urea-formaldehyde adhesives with collagen type hydrolysates under acid condition  

Microsoft Academic Search

Condensation of dimethylol urea and its mixtures with urea or hydrolysate of chrome-tanned leather waste (mass fraction in\\u000a mixture 0.05) in the presence of a variable quantity of phthalic acid, as acid curing agent (within mass fraction limits 0.01-0.1),\\u000a was studied through TG technique. During condensation of sole dimethylol urea or of its mixture with urea, oxy-methylene as\\u000a well as

F. Langmaier; J. Šivarová; K. Kolomazník; M. Mládek

2004-01-01

326

UTILIZATION BY SHEEP OF WHOLE SHELLED CORN IMPREGNATED WITH UREA, CALCIUM, POTASSIUM AND SULFUR  

Microsoft Academic Search

Twenty-eight growing wether lambs (33.9 kg), adapted to urea for 40 d, were used in a metabo- lism study to determine if urea impregnation of corn could improve urea utilization. The following diets were compared: 1) whole shelled corn alone, 2) whole shelled corn impregnated with urea, calcium (Ca) as CaC12, potassium (K) as KC~H302, and sulfur (S) as Na2S203.SH20,

L. L. Koeln; K. E. Webb; J. P. Fontenot

2010-01-01

327

Feeding Urea Through Surface Licking in the Growing Buffalo (Bos bubalis) Calves  

Microsoft Academic Search

Kaur, S. and Kakkar, V.K. 1995. Feeding urea through surface licking in the growing buffalo (Bos bubalis) calves. J. Appl. Anim Res., 8: 129–136A new device, called portable feeder with revolving surface, for the gradual intake of urea-molasses mixture, was compared with urea-molasses-mineral block (uromin-lick) and urea containing concentrate mixture in Murrah buffalo calves. The different groups of calves were

Sukhvir Kaur; V. K. Kakkar

1995-01-01

328

Production of high-quality liquid fertilizers from wet-process acid via urea phosphate  

Microsoft Academic Search

A pilot-plant process is described that purifies wet-process phosphoric acid for the production of a high-quality urea-ammonium polyphosphate base solution. An intermediate product, crystalline urea phosphate, is produced from urea and merchant-grade (54% P2O5) wet-process phosphoric acid. The urea phosphate crystals contain only about 15 to 20% of the objectionable impurities (iron, aluminum, and magnesium) originally contained in the feed

C. A. Hodge; T. W. Motes

1994-01-01

329

Production of high-quality liquid fertilizers from wet-process acid via urea phosphate  

Microsoft Academic Search

A pilot-plant process is described that purifies wet-process phosphoric acid for the production of a high-quality urea-ammonium polyphosphate base solution. An intermediate product, crystalline urea phosphate, is produced from urea and merchant-grade (54% PâOâ) wet-process phosphoric acid. The urea phosphate crystals contain only about 15 to 20% of the objectional impurities (iron, aluminum, and magnesium) originally contained in the feed

C. A. Hodge; T. W. Motes

1991-01-01

330

Production of high-quality liquid fertilizers from wet-process acid via urea phosphate  

Microsoft Academic Search

A pilot-plant process is described that purifies wet-process phosphoric acid for the production of a high-quality urea-ammonium polyphosphate base solution. An intermediate product, crystalline urea phosphate, is produced from urea and merchant-grade (54% P[sub 2]O[sub 5]) wet-process phosphoric acid. The urea phosphate crystals contain only about 15 to 20% of the objectional impurities (iron, aluminum, and magnesium) originally contained in

C. A. Hodge; T. W. Motes

1991-01-01

331

Urearetics: a small molecule screen yields nanomolar potency inhibitors of urea transporter UT-B  

Microsoft Academic Search

Functional studies in knockout mice in- dicate a critical role for urea transporters (UTs) in the urinary concentrating mechanism and in renal urea clearance. However, potent and specific urea transport blockers have not been available. Here, we used high- throughput screening to discover high-affinity, small molecule inhibitors of the UT-B urea transporter. A collection of 50,000 diverse, drug-like compounds was

Marc H. Levin; Ricardo de la Fuente; A. S. Verkman

2007-01-01

332

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

NASA Technical Reports Server (NTRS)

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.

Wydeven, T.; Leban, M.

1973-01-01

333

Effects of urethane, ambient temperature and injection route on rat body temperature and metabolism due to endotoxins.  

PubMed Central

1. We have investigated the influence of environmental temperature, anaesthesia and route of administration on rectal temperature and other metabolic responses to two preparations of bacterial endotoxin in male adult Wistar rats. 2. Urethane anaesthesia, environmental temperatures of 20 and 28 degrees C, subcutaneous (S.C.) and intraperitoneal (I.P.) routes of administration and butanol and trichloroacetic acid (TCA) extracts of E. coli endotoxin (1.2 mg/kg) were used. 3. In addition to rectal temperature, serum zinc, albumin and urea concentrations and liver protein, RNA and zinc contents were measured. 4. Fevers were produced by injections of both endotoxins, by either route at 28 degrees C. Butanol-extracted endotoxin produced a more rapid response than the TCA extract via the I.P. route whereas the TCA extract produced a higher temperature than the butanol extract when the S.C. route was used. 5. Fevers were inhibited at an environmental temperature of 20 degrees C and by anaesthesia, while the former had no effect on compositional changes the latter inhibited the fall in serum zinc in response to subcutaneous doses of either endotoxin and the increase in liver zinc content in response to the butanol extract of endotoxin. 6. At 20 degrees C a marked fall in rectal temperature occurred in conscious rats 2 h after receiving the TCA but not the butanol extract of endotoxin. Temperature depression was more severe when endotoxin was administered by the I.P. route. 7. Serum urea was elevated in conscious rats by the TCA extract of endotoxin via both routes but only by the I.P. route for the butanol extract of endotoxin. In anaesthetized animals only the TCA extract of endotoxin raised serum urea concentration when given intraperitoneally. 8. Serum albumin and liver protein and RNA were unaffected by endotoxin injections over the 7 h time course of the study. 9. Rectal temperature responses to endotoxins were influenced in direction and magnitude by all variables employed in the study, while compositional changes were unaffected by environmental temperature but influenced to varying degrees by urethane anaesthesia and the route of administration employed.

Bibby, D C; Grimble, R F

1988-01-01

334

The Combustive Sound Source  

NASA Astrophysics Data System (ADS)

This thesis describes a unique type of low frequency underwater sound source, the Combustive Sound Source (CSS). The fundamental operating principle of CSS is the following: Electrolysis of water produces hydrogen and oxygen gas, which is a combustible mixture. The gas mixture is captured in a combustion chamber and ignited with a spark. The ensuing combustion produces expanding gases which in turn produce high intensity, low frequency acoustic pulses. The thesis begins by discussing the background of the project and initial feasibility work. It continues by briefly discussing electrolysis and gas production. Fundamental combustion theory is discussed, along with two experiments that relate the acoustic output of CSS to theory. Additional experiments were conducted in order to compare the first bubble period in the CSS pressure signature with the predictions of the Rayleigh-Willis equation. The dependence of the radiated acoustic waveform on the volume and depth of the bubble was investigated. The first bubble period of the CSS pressure signature agrees with Rayleigh-Willis theory in trend, but not in absolute value. Empirical equations are presented which predict the first bubble period for three different situations, a depth of nine meters for various stoichiometric volumes, a stoichiometric volume of 0.5 STP liters for various depths, and a stoichiometric volume of 500 cubic centimeters for various depths. High speed filming of the CSS bubble is presented. The high speed films confirm that CSS produces a bubble of high temperature combustion products. The bubble oscillates and generates acoustic output. The motion of the bubble is shown to be related to the acoustic output in the classic manner, with pressure peaks associated with minimum bubble volumes. Finally, several other factors that affect the acoustic output of CSS are discussed. These include the shape of the CSS combustion chamber, the ignition source, the oxidizer, the presence of high pressure bubble collapses, and the presence of high frequency components.

Wilson, Preston S.

1994-04-01

335

Enantioselective Michael Addition/Iminium Ion Cyclization Cascades of Tryptamine-Derived Ureas  

PubMed Central

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

2013-01-01

336

One-pot synthesis of ureas from Boc-protected amines.  

PubMed

A practical one-pot synthesis of ureas is described. Boc-protected amines can be transformed into nonsymmetrical and symmetrical disubstituted and trisubstituted ureas utilizing 2-chloropyridine and trifluoromethanesulfonyl anhydride for the in situ generation of an isocyanate, which reacts with an amine. A variety of amines can be employed successfully, leading to high yields of isolated ureas. PMID:24750028

Spyropoulos, Constantinos; Kokotos, Christoforos G

2014-05-16

337

Evidence for urea-induced hypometabolism in isolated organs of dormant ectotherms.  

PubMed

Many organisms endure extended periods of dormancy by depressing their metabolism, which effectively prolongs the use of their endogenous energy stores. Though the mechanisms of hypometabolism are varied and incompletely understood, recent work suggests that urea accumulation in autumn and early winter contributes to reduced metabolism of hibernating wood frogs (Rana sylvatica). Urea accumulation during dormancy is a widespread phenomenon, and it has long been presumed that numerous species from diverse taxa benefit from its hypometabolic effect. To investigate the phylogenetic prevalence of urea-induced hypometabolism, we studied four species of urea accumulators from the clades Amphibia (Spea bombifrons and Ambystoma tigrinum), Reptilia (Malaclemys terrapin), and Gastropoda (Anguispira alternata), and one amphibian species (R. pipiens) that does not accumulate urea during dormancy. We measured rates of oxygen consumption (VO(2)) of excised organ samples from dormant animals in the presence or absence of physiological concentrations of urea. Three of the four urea-accumulating species had at least one organ whose VO(2) was significantly decreased by urea treatment. However, VO(2) of organs from R. pipiens, the one species tested that does not accumulate urea during dormancy, was not affected by urea treatment. Our results support the hypothesis that urea accumulation can reduce metabolic rate of dormant animals and provide a base for further investigation into the evolution of urea-induced hypometabolism. PMID:19739087

Muir, Timothy J; Costanzo, Jon P; Lee, Richard E

2010-01-01

338

Recent research on problems in the use of urea as a nitrogen fertilizer  

Microsoft Academic Search

Recent research on the NH3 volatilization, NO2- accumulation, and phytotoxicity problems encountered in the use of urea fertilizer is reviewed. This research has shown that the adverse effects of urea fertilizers on seed germination and seedling growth in soil are due to NH3 produced through hydrolysis of urea by soil urease and can be eliminated by addition of a urease

J. M. Bremner

1995-01-01

339

Use of urease inhibitors to reduce ammonia loss following application of urea to flooded rice fields  

Microsoft Academic Search

Ammonia (NH3) volatilization is an important mechanism for nitrogen (N) loss from flooded rice fields following the application of urea into the floodwater. One method of reducing losses is to use a urease inhibitor that retards the hydrolysis of urea by soil urease and allows the urea to diffuse deeper into the soil. The two chemicals that have shown most

J. R. Freney; D. G. Keerthisinghe; P. Chaiwanakupt; S. Phongpan

1993-01-01

340

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

Microsoft Academic Search

Urea cycle disorders (UCDs) are a group of inborn errors of hepatic metabolism caused by the loss of enzymatic activities that mediate the transfer of nitrogen from ammonia to urea. These disorders often result in life-threatening hyperammonemia and hyperglutaminemia. A combination of sodium phenylbutyrate and sodium phenylacetate\\/benzoate is used in the clinical management of children with urea cycle defects as

Fernando Scaglia; Susan Carter; William E O’Brien; Brendan Lee

2004-01-01

341

75 FR 51440 - Solid Urea from the Russian Federation: Final Results of Antidumping Duty Administrative Review  

Federal Register 2010, 2011, 2012, 2013

...solid urea from the Russian Federation. The...review was produced and exported by MCC...in the ``Issues and Decision Memorandum...Solid Urea from the Russian Federation for the...solid urea from the Russian Federation produced and exported by...

2010-08-20

342

Urea and urotropine conversion in the preparation of microspherical metal oxide particles by internal gelation  

Microsoft Academic Search

The results of studies on urea and urotropine product distribution in solutions formed in microspherical nuclear fuel preparation by internal gelation are presented. It is shown that urea, urotropine and formaldehyde, the urotropine hydrolysis product, undergo various conversions in solutions, resulting in methylolurea and urea-formaldehyde resins formation. Results on the influence of acidity on the process as a function of

A. D. Karpyuk; N. S. Kolyada; A. E. Klyugin

1990-01-01

343

Acute poisoning of silver gulls (Larus novaehollandiae) following urea fertilizer spillage  

Microsoft Academic Search

Two episodes of accidental urea toxicosis are described in wild silver gulls (Larus novaehollandiae) following spillage of fertilizer grade urea at a commercial shipping facility near Perth, Western Australia. In both cases, urea spillage had been seen to contaminate freshwater wash-down pools on the wharves where ships were being unloaded and gulls were seen to be drinking and washing in

Shane R. Raidal; Susan M. Jaensch

2006-01-01

344

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

Code of Federal Regulations, 2010 CFR

...3 2010-01-01 2009-04-01 true Urea-formaldehyde resins in molded articles...Repeated Use Food Contact Surfaces § 177.1900 Urea-formaldehyde resins in molded articles. Urea-formaldehyde resins may be safely...

2010-01-01

345

Urea in exhaled breath condensate of uraemics and patients with chronic airway diseases.  

PubMed

Exhaled breath condensate (EBC) is composed mainly by water and also contains non-volatile mediators, which are expired in small droplets of airway fluid. Urea has been proposed as a normalization factor for EBC non-volatile biomarkers. Aim of this study was to assess volatility and diffusivity of urea ex vivo and to measure its EBC concentrations in different clinical conditions. Volatility was assessed quantifying EBC concentrations collected at 4 different temperatures, whereas diffusivity was tested by measuring urea concentrations in both plasma and EBC from uraemic patients on intermittent haemodialysis. Urea was also measured in EBC from patients with chronic airway diseases, i.e., chronic obstructive pulmonary disease, asthma, and cystic fibrosis. The concentration of urea but not its absolute amount in EBC increased with condensation temperature. Haemodialysis influenced EBC and plasma urea concentrations in a similar way. The concentrations of urea in chronic airway diseases did not significantly differ from those of controls. Urea is a non-volatile molecule ex vivo and EBC urea depends on its concentrations in plasma. Urea concentrations in EBC are unaffected by three chronic airway diseases. We suggest that there is no need to normalize non-volatile biomarkers in EBC for urea concentrations to account for inter-individual variability. However, in repeated measurements within the same individual, the use of urea either as a normalizing factor or as covariate variable could be proposed to control intra-individual variability. PMID:18924313

Folesani, Giuseppina; Corradi, Massimo; Goldoni, Matteo; Manini, Paola; Acampa, Olga; Andreoli, Roberta; Bertorelli, Giuseppina; David, Salvatore; Franchini, Innocente

2008-01-01

346

A Statistical Evaluation of Animal and Nutritional Factors Influencing Concentrations of Milk Urea Nitrogen1  

Microsoft Academic Search

Data from 35 trials with 482 lactating cows fed 106 diets were used to study the effects of animal and dietary factors on the relationship between milk and blood urea N and the value of milk urea N in the assessment of protein status. In two trials, urea N in whole blood and in blood plasma were closely related (r2

Glen A. Broderick; Murray K. Clayton

1997-01-01

347

Urea space and total body water measurements by stable isotopes in patients with acute renal failure  

Microsoft Academic Search

Urea space and total body water measurements by stable isotopes in patients with acute renal failure.BackgroundKnowledge of urea volume of distribution (Vurea) in patients with acute renal failure (ARF) is critical in order to prescribe and monitor appropriate dialytic treatment. We have recently shown that in ARF patients, Vurea estimation by urea kinetic modeling is significantly higher than total body

T. Alp Ikizler; M. Tugrul Sezer; Paul J. Flakoll; SREE HARIACHAR; N. Suren Kanagasundaram; NANCY GRITTER; STEPHANIE KNIGHTS; YU SHYR; EMIL PAGANINI; Raymond M. Hakim; JONATHAN HIMMELFARB

2004-01-01

348

Uphill Transport of Urea in the Dog Kidney: Effects of Certain Inhibitors*  

PubMed Central

To study the renal medullary transport and accumulation of urea in dogs independent of water transport, we obliterated the medullary electrolyte gradient by a sustained ethacrynic acid diuresis. Infusions of urea were also given at various rates to vary urinary urea concentration. In the steady state, the kidneys were removed, and slices were analyzed for water, urea, and electrolytes. In every experiment in 15 dogs over a range of urinary urea concentration from 19 to 230 mmoles per L and urine flow from 0.5 to 9.7 ml per minute per kidney, an intrarenal urea gradient persisted, and urinary urea concentration was always lower than papillary water urea concentration. The magnitude of this uphill urinary-papillary gradient (mean ± SE = - 21 ± 2.9 mmoles per L) was not affected by hemorrhagic hypotension or a nonprotein diet. In 12 additional experiments begun similarly, inhibitors were infused into one renal artery. Both iodoacetate, an inhibitor of anaerobic glycolysis, and acetamide, an analogue of urea, markedly and significantly reduced both the intrarenal urea gradient and the uphill urinary-papillary gradient. In contrast, cyanide, an inhibitor of oxidative metabolism, had no observable effect on the urea gradients. The data are best explained by postulating an active transport system for urea in the medullary collecting duct deriving its energy from anaerobic glycolysis.

Goldberg, Martin; Wojtczak, Andrzej M.; Ramirez, Manuel A.

1967-01-01

349

Glycohaemoglobin measurement: methodological differences in relation to interference by urea.  

PubMed

The aim of this study was to investigate the agreement between a cation-exchange HPLC method and a boronate affinity method of measuring glycohaemoglobin (HbA1c), with particular reference to the effect of elevated urea concentration. HbA1c was measured by both methods in samples from 75 subjects who were classified as diabetic with normal (n=36) or abnormal (n=12) renal function, and non-diabetic with normal (n=8) or abnormal (n=19) renal function. Urea was found to cause a clinically significant interference in the HPLC method at a level > or =17.0 mmol/l. Each increase of 1 mmol/l urea in serum was associated with an absolute increase of 0.04% in the HbA1c value as measured by the HPLC method. The boronate affinity method for HbA1c did not appear to be affected by elevated urea concentration. There was significant correlation (r=0.97, p<0.001) between HbA1c results obtained by the two methods, however, results obtained by the boronate affinity method were generally lower. The discrepancy between results obtained by the two methods was particularly marked in uraemic samples from diabetic subjects, as the HPLC/boronate affinity difference increased as the HbA1c increased and also as the urea concentration increased. Results indicate that blood from diabetic patients with renal failure may give erroneously high HbA1c values by HPLC. Results also highlight the importance of choosing appropriate clinical samples and statistical techniques when evaluating or comparing test methods. PMID:12043937

Lee, K F; Szeto, Y T; Benzie, I F F

2002-04-01

350

Reverse flood routing with the inverted Muskingum storage routing scheme  

NASA Astrophysics Data System (ADS)

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.

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

2012-01-01

351

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

SciTech Connect

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.

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

2007-01-01

352

An assessment of granular urea\\/ammonium sulphate and urea\\/potassium nitrate fertilizers on nitrogen recovery by ryegrass  

Microsoft Academic Search

The comparative effects of ammonium sulphate (AS), potassium nitrate (KNO3), urea (U) or combined 1:1 (w\\/w) U\\/KNO3, U\\/AS granular products were investigated on dry matter (DM) yield and15N utilisation by perennial ryegrass grown under controlled environmental conditions.

Catherine J. Watson

1988-01-01

353

High efficiency RCCI combustion  

NASA Astrophysics Data System (ADS)

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).

Splitter, Derek A.

354

Internal combustion engine  

SciTech Connect

This patent describes an internal combustion engine having a main combustion chamber in a top portion of a piston, and an ignition chamber in a cylinder head, which is provided with a fuel injection valve and an ignition plug, characterized in that the direction in which fuel is ejected from the fuel injection valve is in accordance with the forward direction of a swirl in the main combustion chamber. The axis of the ejected fuel is spaced from a substantially central portion of the main combustion chamber by a distance of not more than 1/2 of the radius thereof. A recess which is in communication with the main combustion chamber is provided in the section of the top portion of the piston which is on an extension of the ignition chamber. The diameter of the ignition chamber is set larger than that of an atomized fuel spray at the outlet thereof. A spark gap of the ignition plug is provided in a position which is spaced by 4 to 10 mm from the center of the spherical end of a nozzle of the fuel injection valve toward the outlet of the ignition chamber, and 2 to 7 mm from the axis of the fuel injection valve in the radial direction of the ignition chamber.

Nagakura, K.

1987-09-15

355

Microgravity Combustion Diagnostics Workshop  

NASA Technical Reports Server (NTRS)

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.

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

1988-01-01

356

Advanced Subsonic Combustion Rig  

NASA Technical Reports Server (NTRS)

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.

Lee, Chi-Ming

1998-01-01

357

Protocol Independent Adaptive Route Update for VANET  

PubMed Central

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.

Rasheed, Asim; Qayyum, Amir

2014-01-01

358

Anonymous Connections and Onion Routing.  

National Technical Information Service (NTIS)

Onion Routing provides anonymous connections that are strongly resistant to both eavesdropping and traffic analysis. Unmodified Internet applications can use these anonymous connections by means of proxies. The proxies may also make communication anonymou...

D. M. Goldschlag M. G. Reed P. F. Syverson

1997-01-01

359

Combustible structural composites and methods of forming combustible structural composites  

DOEpatents

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.

Daniels, Michael A. (Idaho Falls, ID); Heaps, Ronald J. (Idaho Falls, ID); Steffler, Eric D (Idaho Falls, ID); Swank, William D. (Idaho Falls, ID)

2011-08-30

360

Combustible structural composites and methods of forming combustible structural composites  

SciTech Connect

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.

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

2013-04-02

361

External combustion engine having a combustion expansion chamber  

NASA Astrophysics Data System (ADS)

This patent application discloses an external combustion engine having a combustion expansion chamber. The engine includes a combustion chamber for generating a high-pressure, energized gas from a monopropellant fuel, and a cylinder for receiving the energized gas through a rotary valve to perform work on a cylinder disposed therein. A baffle plate is positioned between the combustion area and expansion area for reducing the pressure of the gas. The combustion area and expansion area are separated by a baffle plate having a flow area which is sufficiently large to eliminate the transmission of pressure pulsations from the combustion area to the expansion area while being small enough to provide for substantially complete combustion in the combustion area. The engine is particularly well suited for use in a torpedo.

Duva, Anthony W.

1993-03-01

362

Mobile agents for adaptive routing  

Microsoft Academic Search

This paper introduces AntNet, a new routing algorithm for telecommunication networks. AntNet is an adaptive, distributed, mobile-agents-based algorithm which was inspired by recent work on the ant colony metaphor. We apply AntNet in a datagram network and compare it with both static and adaptive state-of-the-art routing algorithms. We ran experiments for various paradigmatic temporal and spatial traffic distributions. AntNet showed

Gianni Di Caro; M. Dorigo

1998-01-01

363

Ensemble routing for datacenter networks  

Microsoft Academic Search

This paper describes Hash-Based Routing (HBR), an architecture that enhances Ethernet to support dynamic management for multipath networks in scalable datacenters. This work enhances HBR to support flow ensemble management for large-scale networks of arbitrary topology. Ensemble routing eliminates measurement and control for individual flows and instead manages using summary data thus providing a unique capability for reactive datacenter-wide network

Mike Schlansker; Yoshio Turner; Jean Tourrilhes; Alan Karp

2010-01-01

364

Large margin shortest path routing  

Microsoft Academic Search

A new discriminative approach to routing inspired by the large margin criterion serving as a basis for support vector machines\\u000a is presented. The proposed formulation uses the benefit of the dualization convex program, and it is possible for standard\\u000a solvers to learn the weighting metrics of the shortest path routing. In order to demonstrate this and due to its simplicity,

Yadamsuren Lutbat; Rentsen Enkhbat; Won-Joo Hwang

365

Distributed Routing with Labeled Distances  

Microsoft Academic Search

The author presents, verifies, and analyzes a new routing algorithm called the labeled distance-vector routing algorithm (LDR), that is loop-free at every instant, eliminates the counting-to-infinity problem of the distributed Bellman-Ford (DBF) algorithm, operates with arbitrary link and node delays, and provides shortest paths a finite time after the occurrence of an arbitrary sequence of topological changes. In contrast to

J. J. Garcia-luna-aceves

1992-01-01

366

Landscape analysis for multicast routing  

Microsoft Academic Search

In recent years, methods based on local search have been utilized in off-line algorithms for multicast routing in communication networks. In multicast routing, several point-to-multipoint requests have to be scheduled under constraints associated with each link of the underlying network such as capacity and transmission costs. We propose a landscape analysis technique to solve this problem, where each particular request

Mohammed S. Zahrani; Martin J. Loomes; James A. Malcolm; Andreas Alexander Albrecht

2006-01-01

367

Computer experiments on aqueous solutions. VII. Potential energy function for urea dimer and molecular dynamics calculation of 8 mol % aqueous solution of urea  

Microsoft Academic Search

Molecular dynamics calculation (MD) has been carried out for an aqueous solution of urea at 298.15 K and with experimental density value at ordinary pressure by the use of constant temperature technique developed previously. The total number of molecules is 216, of which 17 are urea. The mole fraction of urea in the solution is thus 0.078. For water–water and

Hideki Tanaka; Koichiro Nakanishi; Hidekazu Touhara

1985-01-01

368

The Weak Cytokinins N,N?-bis-(1-naphthyl)urea and N,N?-bis-(2-naphthyl)urea may Enhance Rooting in Apple and Mung Bean  

Microsoft Academic Search

The present research investigates the possibility that 2 weak urea-type cytokinins, the N,N?-bis-(1-naphthyl)urea and the N,N?-bis-(2-naphthyl)urea, enhance adventitious root formation. The rooting activity was assessed using the stem slice test, the mung bean rooting test and the rooting of apple microcuttings. The two compounds influenced the adventitious rooting process differently as regards the bioassay used. In the stem slice test, in

Ricci Ada; Carra Angela; Rolli Enrico; Bertoletti Cristina; Branca Camillo

2005-01-01

369

Studies on morphological and electrical properties of Al incorporated combusted iron oxide  

Microsoft Academic Search

The aluminium incorporated iron oxide samples were prepared by combustion route using aluminium nitrate and ferric trichloride as precursors. The samples were characterized for their morphological, dielectrical, impedance and thermal conductivity properties as a function of temperature. A strong low frequency dielectric dispersion is found to exist in these samples; this is ascribed to the presence of the ionized space

S. S. Shinde; C. H. Bhosale; K. Y. Rajpure

2011-01-01

370

Hybrid rocket combustion study  

NASA Technical Reports Server (NTRS)

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.

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

1993-01-01

371

Droplet Combustion Experiment movie  

NASA Technical Reports Server (NTRS)

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.

2003-01-01

372

Internal combustion engine  

DOEpatents

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.

Baker, Quentin A. (P.O. Box 6477, San Antonio, TX 78209); Mecredy, Henry E. (1630-C W. 6th, Austin, TX 78703); O'Neal, Glenn B. (6503 Wagner Way, San Antonio, TX 78256)

1991-01-01

373

Droplet Combustion Experiment  

NASA Technical Reports Server (NTRS)

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-1R mission (STS-94, July 1-17 1997). Advanced combustion experiments will be a part of investigations plarned for the International Space Station. (120KB JPEG, 655 x 736 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-0300167.html.

2003-01-01

374

Droplet Combustion Experiment  

NASA Technical Reports Server (NTRS)

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. (199KB JPEG, 1311 x 1477 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-0300165.html.

2003-01-01

375

Fluidized-bed combustion  

SciTech Connect

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.

Botros, P E

1990-04-01

376

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

PubMed

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

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

2014-06-01

377

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

PubMed Central

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.

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

2014-01-01

378

Sandia Combustion Research Program: Annual Report, 1979.  

National Technical Information Service (NTIS)

This volume discusses facilities, equipment, and projects in combustion research. Areas covered in the report are: flame studies, diagnostic equipment, internal combustion engines, fossil fuels combustion, and combustion spectroscopy.

M. A. Gusinow D. C. Spencer

1979-01-01

379

Synthesis and characterization of MoO 3 nanostructures by solution combustion method employing morphology and size control  

Microsoft Academic Search

Molybdenum oxide nanostructures were synthesized utilizing the solution combustion method where the ammonium molybdate powder\\u000a and an organic additive were used as precursors. Different organic additives including ethylene diamine tetra-acetic acid\\u000a (EDTA), polyethylene glycol 200 (PEG 200), sorbitol and urea were used as surfactants in order to investigate the effect of\\u000a additive structure on morphology and particle size of products.

D. Parviz; M. Kazemeini; A. M. Rashidi; Kh. Jafari Jozani

2010-01-01

380

Combustion and NO emission of high nitrogen content biomass in a pilot-scale vortexing fluidized bed combustor  

Microsoft Academic Search

The combustion of biomass of various nitrogen contents and its NO emission were investigated experimentally in this study. All the experiments were conducted in an I.D. 0.45m pilot-scale vortexing fluidized bed combustor (VFBC). Rice husk, corn, and soybean were used as feeding materials. Urea was added into the feeding materials for the purpose of adjusting nitrogen content. The effects of

F. P. Qian; C. S. Chyang; K. S. Huang; Jim Tso

2011-01-01

381

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

PubMed

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

Clayden, Jonathan; Lemiègre, Loïc; Helliwell, Madeleine

2007-03-30

382

[Effect of urea on penetration kinetics of vitamin A acid in human skin].  

PubMed

It is well known that urea can considerably increase the release of drugs from ointment bases and that it is one of the most effective penetration promoters for topically applied drugs. In our present study, therefore, we investigated the influence of urea on the penetration kinetics of vitamin A acid (VAA) into the various layers of human skin. When a vehicle containing urea was applied to the skin, we found increased VAA concentrations depending on the penetration of urea. We discuss the significance of the synergistic properties of VAA and urea in the topical treatment of various skin disease. PMID:2264369

Wohlrab, W

1990-09-01

383

Combustibility of tetraphenylborate solids  

SciTech Connect

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.

Walker, D.D.

1989-05-03

384

Studies on Ammonium Perchlorate Combustion.  

National Technical Information Service (NTIS)

This publication contains four articles: The effect of aluminum on the combustion of ammonium perchlorate with polyformaldehyde; Kinetics of the high-temperature thermal decomposition of ammonium perchlorate; Causes for anomalies during combustion of ammo...

A. A. Zenin G. B. Manelis A. P. Glazkova L. D. Romodanova

1969-01-01

385

Municipal Wastewater Sludge Combustion Technology.  

National Technical Information Service (NTIS)

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 polluti...

1985-01-01

386

Combuster. [low nitrogen oxide formation  

NASA Technical Reports Server (NTRS)

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.

Mckay, R. A. (inventor)

1978-01-01

387

A Combustion Laboratory for Undergraduates.  

ERIC Educational Resources Information Center

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)

Peters, James E.

1985-01-01

388

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...

389

Multiobjective Genetic Algorithm for Multicast Routing  

Microsoft Academic Search

This paper presents a multiobjective genetic algorithm to solve the multicast routing problem without using multicast trees. The mechanism to find routes aims to fulfill two conflicting objectives: maximization of the common links in source-destination routes and minimization of the route sizes. The proposed GA can be characterized by representation of network links in a permutation problem, local viability restrictions

Cícero Garrozi; A. F. R. Araujo

2006-01-01

390

Selfish routing and the price of anarchy  

Microsoft Academic Search

Selfish routing is a classical mathematical model of how self-interested users might route traffic through a congested network. The outcome of selfish routing is generally inefficient, in that it fails to optimize natural objective functions. The price of anarchy is a quantitative measure of this inefficiency. We survey recent work that analyzes the price of anarchy of selfish routing. We

Tim Roughgarden

2005-01-01

391

Weighted Epidemic Routing for disruption tolerant networks  

Microsoft Academic Search

Epidemic Routing is an original and effective multicopy routing algorithm in disruption tolerant networks. However, its performance degrades significantly when network resources are limited. In this paper, we proposed a new routing scheme, called Weighted Epidemic Routing (WER). WER appropriately arranges the priority of messages for forwarding or deleting through assigning a weight for each of them when the buffer

Xin Wang; Yantai Shu; Zhigang Jin; Huan Chen

2009-01-01

392

Optimal fully adaptive wormhole routing for meshes  

Microsoft Academic Search

A deadlock-free fully adaptive routing algorithm for 2D meshes which is optimal in the number of virtual chan- nels required and in the number of restrictions placed on the use of these virtual channels is presented. The routing algorithm imposes less than half as many routing restric- tions as any previous fully adaptive routing algorithm. It i s also proved

Loren Schwiebert; D. N. Jayasimha

1993-01-01

393

Routing optimization techniques for communication networks  

Microsoft Academic Search

In this paper, routing optimization techniques for communication networks are discussed. Preventing data loss on overloaded communication links and utilizing link bandwidths efficiently are the main problems of routing techniques. Load balancing and routing problems are solved using genetic algorithms, and simulation techniques. These algorithms work on destination or flow based routing techniques and mainly change the link weight system

A. Emrah Demircan; M. Kemal Leblebiciolu

2005-01-01

394

On two-step routing for FPGAS  

Microsoft Academic Search

We present results which show that a separate global and detailed routing strategy can be competitive with a combined routing pro- cess. Under restricted architectural assumptions, we compute a new lower bound for detailed routing and show that our detailed router typically requires no more than two extra routing tracks above this computed limit. Also, experimental results show that the

Guy G. F. Lemieux; Stephen Dean Brown; Daniel Vranesic

1997-01-01

395

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

PubMed Central

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 ?-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 ?-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.

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

396

Modified aspirated internal combustion engine  

Microsoft Academic Search

An internal combustion engine is described, comprising: an engine block; at least one cylinder; at least one piston, each piston being reciprocally movable in the cylinder; a head connected with the engine block so as to form a combustion chamber above each piston; aspiration means for providing gas entry into and gas exit from the combustion chamber of each cylinder;

1993-01-01

397

Fuels research: Combustion effects overview  

NASA Technical Reports Server (NTRS)

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.

Haggard, J. B., Jr.

1980-01-01

398

Combustion transfer in gasless pyrotechnics  

Microsoft Academic Search

Combustion transfer between gasless pyrotechnics has been studied experimentally and using a simple numerical model of combustion propagation. Implementation of the model requires a knowledge of the thermal and kinetic properties. The kinetic scheme incorporates an Arrhenius temperature dependence that determines the rate of reaction at low temperatures and a diffusion term that controls the high-temperature combustion behavior. A comparison

T. Boddington; A. Cottrell; P. G. Laye

1990-01-01

399

Preemptive routing in Ad Hoc networks  

Microsoft Academic Search

Existing on-demand ad-hoc routing algorithms initiate route discovery only after a path breaks, incurring a significant cost in detecting the disconnection and establishing a new route. In this work, we investigate adding proactive route selection and maintenance to on-demand ad-hoc routing algorithms. More specifically, when a path is likely to be broken, a warning is sent to the source indicating

Tom Goff; Nael B. Abu-Ghazaleh; Dhananjay S. Phatak; Ridvan Kahvecioglu

2001-01-01

400

Dynamically Adaptive Multipath Routing based on AODV  

Microsoft Academic Search

Mobile ad hoc networks are typically char- acterized by high mobility and frequent link failures that result in low throughput and high end-to-end delay. To reduce the number of route discoveries due to such broken paths, multipath routing can be utilized so that alternate paths are available. Current approaches to multipath routing make use of pre-computed routes determined during route

Perumal Sambasivam; Ashwin Murthy; Elizabeth M. Belding-Royer

2004-01-01

401

Combustion Fundamentals Research  

NASA Technical Reports Server (NTRS)

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.

1984-01-01

402

COMBUSTION OF HAZARDOUS WASTE  

EPA Science Inventory

Of the 260 MMT of hazardous waste generated annually in the United States, 1.70 MMT are disposed of in incinerators, 3.50 MMT are burned in boilers and 0.35 MMT are burned in other industrial processes. The paper is an overview of the technologies that can be used to combust haza...

403

Internal combustion engine  

Microsoft Academic Search

An internal combustion engine is described comprising: an engine block defining a cylinder, a cylinder head closing one end of the cylinder, a power piston in the cylinder, a crank shaft journalled in the engine block at the other end of the cylinder, and a connecting rod pivotally connecting the power piston and the crank shaft. The power piston is

Mroz

1987-01-01

404

Internal combustion engine  

Microsoft Academic Search

This patent describes improvement in a 2-cycle, diesel cycle internal combustion engine comprising a single in-line engine block, internal wall surfaces defining at least one cylinder within the engine block, the central longitudinal axis of each cylinder being within a common plane extending longitudinally of the engine block, the axially extending internal wall surface of each cylinder being closed at

H. G. Evans; S. Speer

1991-01-01

405

Regenerated internal combustion engine  

Microsoft Academic Search

A thermally regenerated four-stroke cycle internal combustion engine, is described comprising: a cold side cylinder, having: an intake valve located through cold side cylinder wall for drawing air into the cold side cylinder; an exhaust valve independently located through the cold side cylinder wall for emitting exhaust gases; and a cold side piston connected to a crank shaft through a

1986-01-01

406

Thermoacoustics of unsteady combustion  

Microsoft Academic Search

A longitudinal mode of combustion instability has been studied experimentally and analytically for an advanced aircraft engine combustor system. For the tested configuration, a simple longitudinal acoustic mode consisting of a bulk mode in the inlet section and a traveling wave in the combustor sector section has been identified. The frequencies of oscillations covered a range of 150-380 Hz. A

Jayesh M. Mehta; P. Mungur; W. Dodds; D. Bahr; Steve Clouser

1990-01-01

407

Coal-Slurry Combustion.  

National Technical Information Service (NTIS)

The proceedings of this conference are contained in four volumes. The third volume deals with coal slurry preparation and stabilization and coal slurry combustion and emissions. Papers deal with both coal-oil mixtures (COM) and coal-water slurries (CWS). ...

1982-01-01

408

Internal combustion engine  

Microsoft Academic Search

An internal combustion engine is described comprising: a housing including at least one lobe having a lobe inner surface symmetrically disposed about a lobe axis and conforming to a portion of a spherical surface centered on a lobe center disposed on the lobe axis, wherein a drive shaft aperture intersecting the lobe inner surface is formed through the housing along

Fenton

1986-01-01

409

Combustion properties of biomass  

Microsoft Academic Search

Properties of biomass relevant to combustion are briefly reviewed. The compositions of biomass among fuel types are variable, especially with respect to inorganic constituents important to the critical problems of fouling and slagging. Alkali and alkaline earth metals, in combination with other fuel elements such as silica and sulfur, and facilitated by the presence of chlorine, are responsible for many

B. M Jenkins; L. L Baxter; T. R Miles

1998-01-01

410

Sewage sludge combustion  

Microsoft Academic Search

In the current review paper, various issues related to the combustion of sewage sludge are discussed. After briefly explaining the formation and treatment of sewage sludge, current and future sludge production are discussed. Thereafter, the four sludge disposal methods which are currently used, i.e. recycling in agriculture, landfilling, dumping into sea and incineration, are examined, and the future trend presented

J. Werther; T. Ogada

1999-01-01

411

Monopropellant combustion system  

NASA Technical Reports Server (NTRS)

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.

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

2005-01-01

412

Droplet Combustion Experiment Operates  

NASA Technical Reports Server (NTRS)

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.

2003-01-01

413

ANODR: anonymous on demand routing with untraceable routes for mobile ad-hoc networks  

Microsoft Academic Search

In hostile environments, the enemy can launch traffic analysis against interceptable routing information embedded in routing messages and data packets. Allowing adversaries to trace network routes and infer the motion pattern of nodes at the end of those routes may pose a serious threat to covert operations. We propose ANODR, an anonymous on-demand routing protocol for mobile ad hoc networks

Jiejun Kong; Xiaoyan Hong

2003-01-01

414

Effect of urease inhibitors on urea hydrolysis and ammonia volatilization  

Microsoft Academic Search

Two laboratory incubation experiments were conducted to study the effects of the urease inhibitors hydroquinone (HQ), phenyl phosphorodiamidate (PPDA), and N-(n-butyl) thiophosphoric triamide (NBPT) in retarding the hydrolysis of urea, in the evolution of mineral N, and in reducing NH3 loss through volatilization, under aerobic and waterlogged conditions, both at 25°C. NBPT generally exceeded PPDA and HQ in the ability

Wang Zhengping; O. Van Cleemput; P. Demeyer; L. Baert

1991-01-01

415

Urea-Inorganic Phosphate Mixtures as Prebiotic Phosphorylating Agents  

Microsoft Academic Search

Previous attempts to phosphorylate nucleosides by heating with inorganic phosphate succeeeded only when acid phosphates such as Ca(HPO4)2 were used. The addition of urea and ammonium chloride to the reaction mixture permits phosphorylation in high yield with neutral or basic phosphates at temperatures in the range of 65 degrees to 100 degrees C. Since the abundant mineral, hydroxylapatite, is a

R. Lohrmann; L. E. Orgel

1971-01-01

416

Urea as promoter in the soap flotation of phosphate ores  

Microsoft Academic Search

Phosphate ores containing siliceous gangue minerals are beneficiated by recovering phosphate mineral into froth product by\\u000a using soap or soap-fuel oil emulsion as collector and sodium silicate as depressant. We show here that urea a polar, non electrolyte\\u000a improves both the recovery and grade of phosphate concentrate when used along with the soap-fuel oil emulsion.

D. M. R. Sekhar; K. Srinivas; G. Prabhulingaiah; Yasser Dassin

2009-01-01

417

Property of nano-SiO 2 \\/urea formaldehyde resin  

Microsoft Academic Search

In this paper, we discuss the effects of a nanometer silicon dioxide (nano-SiO2) coupling agent, dispersal methods and the amount of nano-SiO2\\/urea formaldehyde resin. The results of our study indicate that when nano-SiO2, using KH-550 silane as a coupling agent, was added to UF resin by discontinuous ultrasonic vibration, its properties improved\\u000a effectively. When the content of nano-SiO2 was below

Qiaojia Lin; Guidi Yang; Jinghong Liu; Jiuping Rao

2006-01-01

418

In situ poly(urea-formaldehyde) microencapsulation of dicyclopentadiene  

Microsoft Academic Search

Microencapsulated healing agents that possess adequate strength, long shelf-life, and excellent bonding to the host material are required for self-healing materials. Urea- formaldehyde microcapsules containing dicyclopentadiene were prepared by in situ polymerization in an oil-in-water emulsion that meet these requirements for self-healing epoxy. Microcapsules of 10-1000 ?m in diameter were produced by appropriate selection of agitation rate in the range

E. N. BROWN; M. R. KESSLER; N. R. SOTTOS; S. R. WHITE

419

Urushiol\\/polyurethane–urea dispersions and their film properties  

Microsoft Academic Search

A series of aqueous polyurethane–urea (PUU) dispersions having urushiol were synthesized by in situ step polymerization of isophorone diisocyanate (IPDI), poly(ethylene glycol) (PEG, Mn=1000g\\/mol), urushiol, dimethylol propionic acid (DMPA), and ethylene diamine (EDA). Urushiol was extracted with acetone from the purified lacquer of Toxicodendron vernicifluum and the different concentrations (0, 11.8, 17.6, and 22.2wt.% based on the total solids) of

Hyeon Seok Kim; Jeong Hyun Yeum; Sung Wook Choi; Jun Young Lee; In Woo Cheong

2009-01-01

420

Phalaenopsis can absorb urea directly through their roots  

Microsoft Academic Search

Phalaenopsis cultivars are epiphytic orchid plants with high economic value, largely produced across the world as potted plants\\u000a or cut flowers. The goal of this experiment is to show if aseptic (in vitro) Phalaenopsis plants can absorb urea with their\\u000a roots. Young in vitro Phalaenopsis plants were transferred aseptically to a growth medium (solid or liquid) where the three\\u000a forms

Martin Trépanier; Marie-Pierre Lamy; Blanche Dansereau

2009-01-01

421

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

NASA Technical Reports Server (NTRS)

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.

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

1980-01-01

422

Hydrogen bonding of urea-salicylic acid, U·SA  

Microsoft Academic Search

Urea (U) and salicylic acid (SA) crystallize from aqueous solution as a 1:1 adduct whose structure shows them to be linked via several weak and one strong hydrogen bonds. The ir spectra of the adduct and its deuterated counterpart have been analyzed and the stretching modes of the various hydrogen bonds identified. The1H and13C nmr. spectra are also interpreted to

John Emsley; Naser M. Reza; Reiko Kuroda

1986-01-01

423

Colorimetric detection of urea nitrate: The missing link  

Microsoft Academic Search

Traces of the improvised explosive urea nitrate can be characterized by a sensitive colorimetric reaction with p-dimethylaminocinnamalaldehyde (p-DMAC, UN-1 reagent). As recently shown, the dark red product has a structure of a protonated Schiff base. The unprotonated free base, previously postulated in the literature to be the colored product, was now prepared and fully characterized. It shows totally different spectroscopic

Rinat Rozin; Joseph Almog

2011-01-01

424

Potent Urea and Carbamate Inhibitors of Soluble Epoxide Hydrolases  

Microsoft Academic Search

The soluble epoxide hydrolase (sEH) plays a significant role in the biosynthesis of inflammation mediators as well as xenobiotic transformations. Herein, we report the discovery of substituted ureas and carbamates as potent inhibitors of sEH. Some of these selective, competitive tightbinding inhibitors with nanomolar Ki values interacted stoichiometrically with the homogenous recombinant murine and human sEHs. These inhibitors enhance cytotoxicity

Christophe Morisseau; Marvin H. Goodrow; Deanna Dowdy; Jiang Zheng; Jessica F. Greene; James R. Sanborn; Bruce D. Hammock

1999-01-01

425

Reliable, rapid and simple voltammetric detection of urea nitrate explosive.  

PubMed

A highly selective and rapid electrochemical assay of the improvised explosive urea nitrate (UN) is reported. The method involves a short ( approximately 10 s) acid-catalyzed reaction of UN with 4-nitrotoluene (NT) followed by a rapid ( approximately 2 s) square-wave voltammetric (SWV) detection of the 2,4-dinitrotoluene (DNT) product. The new protocol offers great promise for a reliable field detection of UN, with significant advantages of speed, sensitivity, portability, simplicity, and cost. PMID:18427677

Cagan, Avi; Lu, Donglai; Cizek, Karel; La Belle, Jeff; Wang, Joseph

2008-05-01

426

Growth of urea crystals by physical vapor transport  

NASA Technical Reports Server (NTRS)

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.

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

1985-01-01

427

1-(3-Chloro-benz-yloxy)urea  

PubMed Central

The asymmetric unit of the crystal structure of the title compound, C8H9ClN2O2, contains four independent mol­ecules. The dihedral angles between the urea N—(C=O)—N planes and the benzene rings are 83.3?(3), 87.8?(1), 89.1?(1) and 17.5?(2)° in the four mol­ecules. Extensive N—H?O hydrogen bonding is present in the crystal structure.

Mai, Xi; Xia, Hong-Ying; Cao, Yu-Sheng; Tong, Wei; Tu, Guo-Gang

2009-01-01

428

Protein adsorption, lymphocyte adhesion and platelet adhesion\\/activation on polyurethane ureas is related to hard segment content and composition  

Microsoft Academic Search

—Segmented polyurethane ureas with different hard segment content and composition were synthesized using 4,4'-diphenylmethane diisocyanate and polytetramethylene glycols. Using polyols with different molecular weights, it was possible to synthesize polyurethane ureas with either: (i) a constant ratio of urethane to urea bonds; (ii) a constant urethane content; or (iii) a constant urea content. Bulk properties were assessed by dynamic mechanical

TH Groth; K. Klosz; E. J. Campbell; R. R. C. New; B. Hall; H. Goering

1995-01-01

429

Dietary excesses of urea influence the viability and metabolism of preimplantation sheep embryos and may affect fetal growth among survivors  

Microsoft Academic Search

In the first of two experiments investigating the effect of dietary urea on the survival and metabolism of ovine embryos, 30 Border Leicester × Scottish Blackface ewes received a maintenance diet (milled hay, molasses, minerals, vitamins) with no urea (control, C; n = 10) or with added urea at 15 g (low urea, LU; n = 10) or 30 g

T. G. McEvoy; J. J. Robinson; R. P. Aitken; P. A. Findlay; I. S. Robertson

1997-01-01

430

The influence of formula modifications and additives on ammonia loses from surface-applied urea-ammonium nitrate solutions  

Microsoft Academic Search

Urea-ammonium nitrate (UAN) solution fertilizers are subject to N loss through ammonia (NH3) volatilization. This loss may be reduced by manipulation of the proportion of urea and by use of additives to reduce urea hydrolysis or increase fertilizer solution acidity. This research was design to study the effect of urea proportion in UAN solutions, added ammonium thiosulfate (ATS), and aquechem

T. AL-Kanani; A. F. Mackenzie; H. Blenkhorn

1990-01-01

431

Feeder bus route design problem  

SciTech Connect

The US transit industry is in a financial crisis, caused primarily by the rising operating cost and shrinking resources. Among the deficit-reducing strategies that have been proposed, a better integrated transit system has significant advantages in that it offers the possibility of simultaneously reducing cost and increasing revenue. This research develops an optimization-based methodology for the design of an integrated feeder bus/rail transit system. The proposed methodology includes two types of models, an analytic model and a network model. The study defines the Feeder Bus Route Design Problem (FBRDP) as that of locating bus routes and bus stops as well as determining the service characteristics of a feeder bus system, designed to access an existing rail system. The proposed analytic model provides approximate values for the optimal route density, operating headway and bus stop spacing. Within the network approach, the author considers demand with a single (many-to-one) and with multiple (many-to-many) destinations. The network optimization models for the FBRDP are routing-type models that cannot be solved exactly and need to be solved heuristically. A two-phase heuristic is developed that can be viewed as a generalization of the sequential-savings approach to vehicle routing.

Kuah, G.K.

1986-01-01

432

European Route of Industrial Heritage  

NSDL National Science Digital Library

The European Route of Industrial Heritage (ERIH) was started in 2003, and it quickly gained the cooperation of the three countries (Belgium, Great Britain and Germany) that were the heart of the Industrial Revolution. The ERIH brought together non-profits, academic institutions, and tourism organizations with the goal to "protect Europe's industrial heritage sites and use their preservation as a motor for the development of regions that are often suffering from economic decline." Visitors will enjoy the thoroughness of the ERIH's website, which offers an "Industrial History" of Europe. The links on the left hand menu for "Route System", "Anchor Points", "Regional Routes" and "European Theme Routes" offer different ways for visitors to view the industrial revolution, whether by the types of products produced or the size of their contribution to the industrial revolution. Each section has a map associated with it as well. Finally, the "Photo Gallery" links to photos of many of the industrial sites on the above routes, so visitors can see the beauty and uniqueness of these factories that forever changed how various goods were made.

433

Central East Pacific Flight Routing  

NASA Technical Reports Server (NTRS)

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.

Grabbe, Shon; Sridhar, Banavar; Kopardekar, Parimal; Cheng, Nadia

2006-01-01

434

Developing hypothetical inhibition mechanism of novel urea transporter B inhibitor.  

PubMed

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

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

2014-01-01

435

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

NASA Astrophysics Data System (ADS)

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.

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

2014-06-01

436

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

Microsoft Academic Search

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 m·h·m, total gas flow

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

2012-01-01

437

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

DOEpatents

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.

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

2012-05-15

438

Heat regenerative external combustion engine  

NASA Astrophysics Data System (ADS)

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.

Duva, Anthony W.

1993-10-01

439

Flame combustion of carbonaceous fuels  

SciTech Connect

A method for improving the flame combustion of carbonaceous fuels. The method enables the reduction of oxides of nitrogen generated by the flame combustion, and enables an improvement in boiler efficiency. An ionic sodium or potassium compound, or a combination of them, is supplied with the combustible mixture of fuel and air so as intimately and uniformly to be present where and when the flame exists. Preferably the compound is supplied in an aqueous solution, and can be intimately mixed with the fuel, or with the atomizing air or steam, or with the combustion air. The process is useful with both single-stage and staged (multiple-staged) combustion systems.

Hampton, W.J.; Hatch, R.L.; James, G.R.

1984-05-08

440

Elastase-induced hydrolysis of synthetic solid substrates: poly(ester-urea-urethane) and poly(ether-urea-urethane).  

PubMed

Human neutrophil elastase (HNE) and porcine pancreatic elastase (PPE) were incubated with two radiolabelled model poly(urethane), a poly(ester-urea-urethane) containing [14C]toluene diisocyanate ([14C]TDI), poly(caprolactone)(PCL) and ethylenediamine (ED), and a poly(ether-urea-urethane) containing [14C]TDI, poly(tetramethylene oxide) (PTMO) and ED. Ten-fold more radioactive carbon was released when PPE was incubated with [14C]TDI/PCL/ED than when HNE was used. The PPE-induced radioactive carbon release was significantly reduced by a specific elastase inhibitor. Ten-fold less radioactive carbon was released when [14C]TDI/PTMO/ED was incubated with PPE as compared to [14C]TDI/PCL/ED. Since neutrophils, which contain elastolytic activity, are present during the inflammatory response, the stability of biomaterials used in implanted devices may be affected. PMID:8982479

Labow, R S; Erfle, D J; Santerre, J P

1996-12-01

441

Effect of a test meal on the intragastric distribution of urea in the 13C-urea breath test for Helicobacter pylori  

Microsoft Academic Search

Test meals are invariably used in the 13C-urea breath test (UBT) but their effect on the intragastric distribution and gastric residence time of urea given in the test is unknown. The site of Helicobacter pylori urease measured in the test is unknown and whether the test measures total or regional gastric urease is uncertain. This study reports the results of

J C Atherton; P E Blackshaw; J L Greaves; A C Perkins; C J Hawkey; R C Spiller

1995-01-01

442

The comparative effects of ammonium nitrate, urea or a combined ammonium nitrate\\/urea granular fertilizer on the efficiency of nitrogen recovery by perennial ryegrass  

Microsoft Academic Search

The comparative effects of ammonium nitrate (AN), urea or a combined 1:1 (w\\/w) AN\\/urea granular fertilizer with two different fillers (CaCO3 or silica) were investigated on the efficiency of dry matter production and15N recovery by perennial ryegrass grown in pots under controlled environmental conditions.

Catherine J Watson

1987-01-01

443

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

PubMed Central

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.

2011-01-01

444

Alkylation of prohibitin by cyclohexylphenyl-chloroethyl urea on an aspartyl residue is associated with cell cycle G1 arrest in B16 cells  

PubMed Central

Background and purpose: Phenyl-chloroethyl ureas (CEUs) are a class of anticancer drugs that mainly react with proteins. Two molecules of this family, cyclohexylphenyl-chloroethyl urea (CCEU) and iodophenyl-chloroethyl urea (ICEU) induced G1/S and G2/M cell cycle blocks, respectively. We hypothesised that these observations were linked to a differential protein alkylation pattern. Experimental approach: Proteins from B16 cells incubated with [14C-urea]-CCEU and [125I]-ICEU were compared by 2D-analyses followed by MALDI-TOF identification of modified proteins and characterisation of the CCEU binding. Protein expression was investigated by Western blot analyses and cell cycle data were obtained by flow cytometry. Key results: Several proteins (PDIA1, PDIA3, PDIA6, TRX, VDAC2) were alkylated by both ICEU and CCEU but ?-tubulin and prohibitin (PHB) were specifically alkylated by either ICEU or CCEU respectively. Specific alkylation of these two proteins might explain the observed difference in B16 cell cycle arrest in G2 and G1 phases respectively. Mass spectrometry studies on the alkylated prohibitin localised the modified peptide and identified Asp-40 as the target for CCEU. This alkylation induced an increased cellular content of PHB that should contribute to the accumulation of cells in G1 phase. Conclusions and implications: This study reinforces our findings that CEUs alkylate proteins through an ester linkage with an acidic amino acid and shows that PHB alkylation contributes to G1/S arrest in CCEU treated B16 cells. Modification of PHB status and/or activity is an open route for new cancer therapeutics.

Bouchon, B; Papon, J; Communal, Y; Madelmont, J-C; Degoul, F

2007-01-01

445

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

PubMed Central

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.

Eicher, R; Bouchard, E; Tremblay, A

1999-01-01

446

Transport and transformation of de-icing urea from airport runways in a constructed wetland system.  

PubMed

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

Thorén, A K; Legrand, C; Herrmann, J

2003-01-01

447

The molecular basis for the chemical denaturation of proteins by urea  

PubMed Central

Molecular dynamics simulations of the protein chymotrypsin inhibitor 2 in 8 M urea at 60°C were undertaken to investigate the molecular basis of chemical denaturation. The protein unfolded rapidly under these conditions, but it retained its native structure in a control simulation in water at the same temperature. The overall process of unfolding in urea was similar to that observed in thermal denaturation simulations above the protein's Tm of 75°C. The first step in unfolding was expansion of the hydrophobic core. Then, the core was solvated by water and later by urea. The denatured structures in both urea and at high temperature contained residual native helical structure, whereas the ?-structure was completely disrupted. The average residence time for urea around hydrophilic groups was six times greater than around hydrophobic residues and in all cases greater than the corresponding water residence times. Water self-diffusion was reduced 40% in 8 M urea. Urea altered water structure and dynamics, thereby diminishing the hydrophobic effect and encouraging solvation of hydrophobic groups. In addition, through urea's weakening of water structure, water became free to compete with intraprotein interactions. Urea also interacted directly with polar residues and the peptide backbone, thereby stabilizing nonnative conformations. These simulations suggest that urea denatures proteins via both direct and indirect mechanisms.

Bennion, Brian J.; Daggett, Valerie

2003-01-01

448

Preferential Solvation in Urea Solutions at Different Concentrations: Properties from Simulation Studies  

PubMed Central

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.

Kokubo, Hironori; Pettitt, B. Montgomery

2008-01-01

449

Preferential Solvation in Urea Solutions at Different Concentrations: Properties from Simulation Studies  

SciTech Connect

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.

Kokubo, Hironori; Pettitt, Bernard M.

2007-04-21

450

Preferential Solvation in Urea Solutions at Different Concentrations: Properties from Simulation Studies.  

SciTech Connect

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.

Kokubo, Hironori; Pettitt, Bernard M.

2007-02-15

451

A routing vector method (RVM) for routing in Bluetooth scatternets  

Microsoft Academic Search

Bluetooth is a promising new technology for short range wireless connectivity between mobile devices. Initially, Bluetooth will be used as a replacement for point to-(multi)point cables. However, in due course of time, solutions for forming multihop ad hoc networks over Bluetooth (referred to as scatternets) will be needed. In this paper, we explore the design space of routing protocols over

Pravin Bhagwat; Adrian Segallt

1999-01-01

452

Reverse iontophoresis of urea in health and chronic kidney disease: a potential diagnostic and monitoring tool?  

PubMed Central

Background Patients with chronic kidney disease (CKD) need regular monitoring, usually by blood urea and creatinine measurements, needing venepuncture, frequent attendances and a healthcare professional, with significant inconvenience. Noninvasive monitoring will potentially simplify and improve monitoring. We tested the potential of transdermal reverse iontophoresis of urea in patients with CKD and healthy controls. Methods Using a MIC 2® Iontophoresis Controller, reverse iontophoresis was applied on the forearm of five healthy subjects (controls) and 18 patients with CKD for 3–5 h. Urea extracted at the cathode was measured and compared with plasma urea. Results Reverse iontophoresis at 250 ?A was entirely safe for the duration. Cathodal buffer urea linearly correlated with plasma urea after 2 h (r = 0·82, P < 0·0001), to 3·5 h current application (r = 0·89, P = 0·007). The linear equations y = 0·24x + 1 and y = 0·21x + 4·63 predicted plasma urea (y) from cathodal urea after 2 and 3 h, respectively. Cathodal urea concentration in controls was significantly lower than in patients with CKD after a minimum current application of 2 h (P < 0·0001), with the separation between the two groups becoming more apparent with longer application (P = 0·003). A cathodal urea cut-off of 30 ?M gave a sensitivity of 83·3% and positive predictive value of 87% CKD. During haemodialysis, the fall in cathodal urea was able to track that of blood urea. Conclusion Reverse iontophoresis is safe, can potentially discriminate patients with CKD and healthy subjects and is able to track blood urea changes on dialysis. Further development of the technology for routine use can lead to an exciting opportunity for its use in diagnostics and monitoring.

Ebah, Leonard M; Read, Ian; Sayce, Andrew; Morgan, Jane; Chaloner, Christopher; Brenchley, Paul; Mitra, Sandip

2012-01-01

453

Benefits of different urea supplementation methods on the production performances of Merino sheep.  

PubMed

The impact of urea supplementation of sheep feed was examined in two experiments. In Experiment 1, 48 8-month-old Merino wethers were randomised into three groups by liveweight and each group was fed one of three diets: (1) untreated oaten chaff hay; (2) hay treated with urea in-paddock (pre-experiment); or (3) hay treated with a 2% urea solution using a feed mixer. In Experiment 2, 48 4-month-old Merino ewes were randomised into three groups and each group received one of the following roughages: (1) untreated oaten chaff hay, (2) hay treated with a 2% urea solution in a feed mixer, or (3) a 20?kg urea lick block. Both experiments lasted 40 days, and sheep liveweight (kg), average feed intake (g/day), average daily gain (ADG) and body condition score (BCS) were recorded. Ruminal fluid and blood samples were collected on days 20 and 40 from animals in Experiment 1. Sheep supplemented with additional urea had a greater average dry matter (DM) intake (Experiment 1, P?=?0.038; Experiment 2, P?=?0.001), ADG (Experiment 1, P?=?0.043; Experiment 2, P?=?0.041) and average final liveweight (Experiment 1, P?=?0.048), compared to sheep receiving no additional supplementary urea. On both days 20 and 40 in Experiment 1, blood analyses revealed that urea supplemented sheep had elevated levels of urea, creatine kinase and total protein (P?<0.05). Urea supplementation most likely influenced blood urea and total protein concentrations, as supplemented sheep had an increased crude protein intake (through increased feed intake of urea treated roughage with a higher crude protein percentage). By providing additional urea, the DM intake of sheep in both experiments was increased and offers a practical strategy when providing supplementation to sheep. The practice can benefit sheep production by increasing the nutritional value and digestibility of low energy crop stubbles, when fed over dry summer months to help maintain BCS. PMID:24792451

Sweeny, Joshua P A; Surridge, Victoria; Humphry, Pia S; Pugh, Harriet; Mamo, Kristen

2014-06-01

454

A tool for debugging internet multicast routing  

SciTech Connect

In this paper the authors describe a debugging tool that is an effective means of analyzing problems with multicast packet routing in a network. Multicast packet routing is a source-driven distributed calculation performed by the routers in a multicast network. The routes taken by multicast packets are difficult to predict manually due to the large number of variables that must be considered. The multicast route debugging tool allows off-line investigation of the route taken by a multicast packet and the effects of network modifications on that route. The tool has already proved useful in debugging the problems that have occurred in the experimental Internet Multicast Backbone. The multicast route debugging tool currently predicts multicast routes of packets using the distance-vector truncated-broadcast algorithm implemented for Internet multicast traffic. They will be upgrading the tool to allow the user to choose other multicast routing algorithms.

Agarwal, D.; Floyd, S.

1994-03-01

455

Combustion synthesis and properties of fine particle fluorescent aluminous oxides  

Microsoft Academic Search

Fine particle fluorescent aluminous oxide materials like Cr3+-doped ?-Al2O3 (ruby), MgAl2O4, LaAlO3, Y3Al5O12 and Ce3+-doped Y3Al5O12, LaMgAl11O19, CaAl12O19 and CeMgAl11O19 have been prepared by the combustion of the corresponding metal nitrate-aluminium nitrate-urea\\/carbohydrazide mixtures at\\u000a 500°C in less than 5 min. Formation of these Cr3+- and Ce3+-doped aluminous oxides has been confirmed by their characteristic XRD, colour, UV-visible and fluorescence spectra

J J Kingsley; N Manickam; K C Patil

1990-01-01

456

Principles of combustion engineering for boilers  

SciTech Connect

A reference work for those seeking guidance on the choice of combustion equipment, as well as for those wishing to direct their research towards the critical unsolved problems of combustion equipment design. CONTENTS include: Matching the Combustion Equipment to the Boiler; The Combustion of Heavy Fuel Oils; The Combustion of Coal as Pulverised Fuel through Swirl Boilers; The Combustion of Coal-Liquid Mixtures; Cyclone Combustors; and The Combustion of Coal in Fluidised Beds.

Lawn, C.J.

1987-01-01

457

Combustion of Gaseous Mixtures  

NASA Technical Reports Server (NTRS)

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.

Duchene, R

1932-01-01

458

Combustion engine system  

NASA Technical Reports Server (NTRS)

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.

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

1986-01-01

459

Stratified combustion engine  

SciTech Connect

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

Solheim, R.G.

1987-03-17

460

Dynamic features of combustion  

NASA Technical Reports Server (NTRS)

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.

Oppenheim, A. K.

1985-01-01

461

Nitrous oxide combustion chemistry  

SciTech Connect

To gain improved understanding of N2O combustion chemistry, experimentation and numerical modeling were performed, and are described. Principal conclusions are: (1) N2O emission is quite temperature dependent, and (2) for lean, homogeneous combustion systems with peak temperatures higher than 1200 K and without rapid cooling, N2O emission is low. Thermochemical property variations have substantial effects on calculated species profiles. Changes in enthalpies of formation of NH, NH2, and NNH resulted in large differences in predicted NO, N2, and N2O concentrations. Measurements were made in lean, premixed, and atmospheric pressure flat flames by microprobe sampling and gas chromatographic or chemiluminescence analysis. With 2000 ppm of either NH3, NO, or N2O added to the reactants, N2O was observed at moderate concentrations near the burner surface, and a monotonically decreasing concentrations downstream. With NH3 as dopant, early- and post-flame N2O concentration varied inversely with temperature, as did its decay rate. With N2O as dopant, product branching to NO and N2 was 8 and 92 percent. Sensitivity and rate data indicated the primary N2O formation and destruction reactions to be NH + NO = N2O + H and H + N2O = N2 + OH, and that H + O2 + M = HO2 + M plays an important role in trapping H atoms to enhance N2O survival. Flash-ignited combustion experiments were performed and studied. A mixture, where NH3 was primary photolysis absorber and fuel species, burned inhomogeneously. Concentration profiles of N2, NO, O2, and N2O were recorded. N2O added to the reactants disappeared during combustion. Post-flame NO and N2 concentrations were higher than previously reported NH3 flames, but their ratio agreed well with earlier results.

Martin, R.J.

1989-01-01

462

Refractivity of combustion gases  

SciTech Connect

A comprehensive survey of the refractive indices and dispersions of gases that are found in practical or laboratory combustion experiments is reported. A critical evaluation was used to obtain recommended values where experimental data are available. Where they are not, sums of atomic and bond refractivities were used. The results are tabulated as molar refractivities at common laser wavelengths and as the constants of Cauchy dispersion formulas.

Gardiner, W.C. Jr.

1981-02-01

463

Spray atomization and combustion  

NASA Technical Reports Server (NTRS)

New theoretical and experimental methods for studying sprays are reviewed. Common methods to analyze dilute sprays are described and used to interpret recent measurements of the structure of dilute sprays and related dispersed turbulent jets. Particle-laden jets, nonevaporating, evaporating, and combusting sprays, and noncondensing and condensing bubbly jets are examined and used to initially evaluate current analytical methods for a wide range of conditions. Dense sprays are briefly discussed.

Faeth, G. M.

1986-01-01

464

Combustion of viscous hydrocarbons  

Microsoft Academic Search

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° API or less, viscosity of about 1000 centipoise or greater at 212°F., a paraffin

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

1987-01-01

465

Combustion of viscous hydrocarbons  

Microsoft Academic Search

A method is described for utilizing viscous hydrocarbons as combustible fuels comprising: (A) forming a hydrocarbosol using a surfactant package in a proportion of about 1:100 to about 1:20,000 by weight based on hydrocarbon, (1) the surfactant package comprising (a) at least one water-soluble surfactant, an effective amount of which surfactant promotes emulsification of a hydrocarbon with API gravity of

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

1986-01-01

466

Combustion powered linear actuator  

DOEpatents

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.

Fischer, Gary J. (Albuquerque, NM)

2007-09-04

467

Catalytic Combustion of Syngas  

Microsoft Academic Search

The catalytic combustion of syngas\\/air mixtures over Pt has been investigated numerically in a channel-flow configuration using 2D steady and transient computer codes with detailed hetero-\\/homogeneous chemistry, transport, and heat transfer mechanisms in the solid. Simulations were carried out for syngas compositions with varying H2 and CO contents, pressures of 1 to 15 bar, and linear velocities relevant to power

John Mantzaras

2008-01-01

468

Selfish Routing in Capacitated Networks  

Microsoft Academic Search

According to Wardrop's first principle, agents in a congested network choose their routes selfishly, a behavior that is captured by the Nash equilibrium of the underlying noncooperative game. A Nash equilibrium does not optimize any global criterion per se, and so there is no apparent reason why it should be close to a solution of minimal total travel time, i.e.

José R. Correa; Andreas S. Schulz; Nicolás E. Stier Moses

2004-01-01

469

IMPROVED STAINLESS STEEL PROCESSING ROUTES  

Microsoft Academic Search

Advanced melting technology is now being employed in the manufacture of stainless steel powders. The new process currently includes electric arc furnace (EAF) technology in concert with Argon Oxygen Decarburization (AOD), High Performance Atomizing (HPA) and hydrogen annealing. The new high performance processing route has allowed Hoeganaes Corporation to provide not only a more consistent product, but has allowed enhanced

Chris Schade; Robert Causton; Tina Cimino-Corey

470

Dynamic Weather Routes Architecture Overview  

NASA Technical Reports Server (NTRS)

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.

Eslami, Hassan; Eshow, Michelle

2014-01-01

471

Pta en Route Noise Measurements.  

National Technical Information Service (NTIS)

A long-range advanced turboprop en route noise database was obtained with weather, tracking, and onboard measurements. In-flight noise directivity measurements were made. Data repeatability within a test day was excellent. Day-to-day variability existed a...

W. L. Willshire D. P. Garber

1990-01-01

472

Judaism and the Silk Route.  

ERIC Educational Resources Information Center

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)

Foltz, Richard

1998-01-01

473

Routing By Mixed Set Programming  

Microsoft Academic Search

This paper presents the solution to a routing problem (Pick-up and Delivery with Time Windows) by Mixed Set Programming which solves constraint satisfaction problems over a mixed domain of reals, integers, Booleans, references and sets (8). To illustrate the method, a complete constraint program in the NCL language (7, 9) is presented.

Jianyang Zhou

2009-01-01

474

Routes to chemical plaque control  

Microsoft Academic Search

A logical approach to the prevention of periodontal disease is through excellent supragingival plaque control. Such control is not generally achieved by mechanical oral hygiene procedures alone. Thus, there is a clear rationale for the use of antiplaque agents to augment mechanical means. The principle routes to chemical plaque control are to prevent colonization of the tooth surface, to inhibit

D. Cummins

1991-01-01

475

AODV Routing Protocol Implementation Design  

Microsoft Academic Search

To date, the majority of ad hoc routing protocol research has been done using simulation only. One of the most moti- vating reasons to use simulation is the difculty of creating a real implementation. In a simulator, the code is contained within a single logical component, which is clearly dened and accessible. On the other hand, creating an implemen- tation

Ian D. Chakeres; Elizabeth M. Belding-royer

2004-01-01

476

Daily Aircraft Routing and Scheduling  

Microsoft Academic Search

In this paper we consider the daily aircraft routing and scheduling problem (DARSP). It consists of determining daily schedules which maximize the anticipated profits derived from the aircraft of a heterogeneous fleet. This fleet must cover a set of operational flight legs with known departure time windows, durations and profits according to the aircraft type. We present two models for

Guy Desaulniers; Jacques Desrosiers; Yvan Dumas; Marius M. Solomon; François Soumis

1997-01-01

477

The Diesel Combustion Collaboratory: Combustion Researchers Collaborating over the Internet  

SciTech Connect

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.

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

2000-02-01

478

Droplet Combustion Experiment (DCE)  

NASA Technical Reports Server (NTRS)

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.

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

1998-01-01

479

Internal combustion engine  

SciTech Connect

An internal combustion engine is described comprising: a housing including at least one lobe having a lobe inner surface symmetrically disposed about a lobe axis and conforming to a portion of a spherical surface centered on a lobe center disposed on the lobe axis, wherein a drive shaft aperture intersecting the lobe inner surface is formed through the housing along a drive shaft axis extending radially from the lobe center at an angle to the lobe axis; a vane support ring mounted in the housing to extend circularly about the lobe axis for rotation about the lobe axis; a vane mounted on the vane support ring for pivotation about a selected diameter of the vane support ring passing through the lobe center, the vane having a sealing surface formed thereon to mate with the lobe inner surface and the sealing surface extending arcuately about the lobe center between opposite ends of the selected diameter of the vane support ring, wherein the vane support ring is characterized as including means for blocking fluid communication between opposite sides of the vane such that the vane divides the interior of the lobe into a first combustion chamber to one side of the vane and a second combustion chamber to the other side of the vane.

Fenton, J.W.

1986-05-20

480

Engine combustion chamber structure  

SciTech Connect

This patent describes a combustion chamber structure comprising an upper wall surface which is shaped like a pent-roof and into which an intake passage opens, a piston having on a head portion thereof a bulged portion conforming to the upper wall surface in shape, a first bowl portion which is formed substantially at the center of the bulged portion and which is substantially semispherical in shape, a pair of second bowl portions which respectively extend on opposite sides of the first bowl portion to the corresponding ends of the bulged portion of the piston along the edge of the bulged portion and are in communication with the first bowl portion, a swirl generating means which is adapted to generate a swirl of intake air in the combustion chamber when the engine load is light, and a spark plug disposed to substantially face the center of the first bowl portion from the upper wall surface; the swirl generating means being adapted to generate the swirl of intake air in a tangential direction in the combustion chamber; and the diameter of the first bowl portion being larger than the width of the second bowl portion.

Tanaka, H.

1988-09-13

481

Pressure-gain combustion  

SciTech Connect

Pulse combustion has been proposed for gas turbine applications in many early articles and more recently has been demonstrated to produce so-called ``pressure-gain`` in a small gas turbine. The basic concept is that the oscillatory combustion occurs as a constant-volume process, producing a gain in the stagnation pressure of air flowing through the combustor, rather than the pressure loss associated with conventional, steady combustion. If properly utilized, this pressure-gain could enhance simple-cycle gas turbine efficiency several percent, depending on the operating conditions. In addition, pulse combustors have demonstrated relatively low NO{sub x} pollutant levels in some applications. The combined potential for higher cycle efficiency and lower pollutant levels is the basis for the present investigation. Tests in progress at the Morgantown Energy Technology Center (METC) have considered a baseline pulse combustor configuration that has shown good oscillating performance, low NO{sub x} emissions, but disappointing results in terms of pressure-gain. However, a combination of numeric simulations and test data suggest that pressure-gain can be produced by a select combination of operating conditions and combustor geometry, but is especially sensitive to the combustor inlet geometry. Tests in progress will evaluate the effect of inlet geometry and operating pressure on both pollutant emissions and pressure-gain.

Richards, G.A.; Yip, J.; Gemmen, R.S.; Janus, M.C.; Norton, T. [USDOE Morgantown Energy Technology Center, WV (United States); Rogers, W.A. [EG and G Washington Analytical Services Center, Inc., Morgantown, WV (United States)

1993-11-01

482

Spray combustion modeling  

NASA Technical Reports Server (NTRS)

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.

Bellan, J.

1997-01-01

483

Device for improved combustion  

SciTech Connect

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.

Polomchak, R.W.; Yacko, M.

1988-03-08

484

Spray combustion stability  

NASA Technical Reports Server (NTRS)

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.

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

1995-01-01

485

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

SciTech Connect

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.

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

1988-09-01

486

Slow adaptive changes in urease levels of tobacco cells cultured on urea and other nitrogen sources  

SciTech Connect

Tobacco (ev. Xanthi) XD cells cultured for more than a year on urea as the sole source of nitrogen have urease activities about four times higher than cells which have been cultured on nitrate. When cells which had always been grown on nitrate were transferred to urea, the urease activity in these cells remained at a lower level for eight transfers (40 generations), then gradually increased 4-fold during the next seven to 10 transfers. Cells with high urease activity multiplied 19% more rapidly and accumulated less urea than cells with low urease activity. These findings suggest that elevated urease accelerates urea assimilation; therefore, urea limited growth. It is suggested that the molecular basis of the urease increase may be gene amplification, based on animal cell models. An alternative hypothesis, namely a specific response induced in all cells b