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1

Reductive alkylation of urea: A practical route to substituted ureas  

Microsoft Academic Search

Conditions are disclosed for the formation of either mono- or di-substituted ureas by reductive alkylation, which are readily adaptable to large scale preparations. Dehydrating agents such as acetyl chloride or trimethylsilyl chloride effectively promote the condensation of ureas and aldehydes. Reduction of the adducts affords the mono- or di-substituted ureas in high yields.

Daqiang Xu; Lech Ciszewski; Tangqing Li; Olijan Repi?; Thomas J. Blacklock

1998-01-01

2

Pulsatile urea excretion in the ureagenic toadfish Opsanus beta: an analysis of rates and routes  

PubMed

This study focused on the rates and routes of urea-N and ammonia-N excretion in the ureagenic toadfish and on the possibility that urea-N excretion occurs in pulses. Experimental approaches included the following: confinement in small individual containers with automated hourly sampling of water to follow temporal excretion patterns; divided chambers to separate excretion from the anterior and posterior parts of the fish; collection of urine and rectal fluid via chronic indwelling catheters; and gavage with [14C]-labelled polyethylene glycol 4000 to detect regurgitation of gastrointestinal fluids. When a standardized 'crowding' pre-treatment was employed to induce ureotelic behaviour, the fish exhibited significant elevations in the activity of glutamine synthetase in liver, kidney and gills, elevated plasma and bile urea-N levels, but unchanged ammonia-N and urea-N levels in most other body fluids. Unencumbered ureotelic fish confined in small containers excreted 82 % of their waste-N as urea-N and 18 % as ammonia-N; almost all (94 %) of this urea-N excretion occurred in a single pulse of less than 3 h duration about once every 24 h. This daily pulse did not occur by regurgitation of gut fluids, by excretion through prominent pores behind the pectoral fins or by discharge of rectal fluid or urine. Intestinal and urinary excretion accounted for less than 10 % of whole-body urea-N excretion and a negligible fraction of ammonia-N excretion. Pulsatile urea-N excretion occurred at the head end across the gills and/or body surface. Ammonia-N excretion, which was not pulsatile, also occurred largely through the head end. However, once the toadfish had been placed in divided chambers, urea-N excretion became continuous rather than pulsatile, and ammonia-N excretion increased greatly. A severe stress response was indicated by high levels of plasma cortisol, and the skin, which lacks scales, became a significant route of both ammonia-N and urea-N excretion. We speculate that the normal adaptive significance is that ureotelism facilitates cryptic behaviour, allowing the toadfish to virtually eliminate N-waste excretion during long periods while it remains sheltered in burrows. However, during severe stress, the effects of extremely high cortisol levels overwhelm the ammonia and urea retention mechanisms, and both substances leak across the general body surface. PMID:9319637

Wood; Hopkins; Hogstrand; Walsh

1995-01-01

3

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

4

Synthesis of Mo and W carbide and nitride nanoparticles via a simple "urea glass" route.  

PubMed

A simple, inexpensive, and versatile route for the synthesis of metal nitrides and carbides (such as Mo2N, Mo2C, W2N and WC) nanoparticles was set up. For the first time, metal carbides were obtained using urea as carbon-source. MoCl5 and WCl4 are in a first step contacted with alcohols and an appropriate amount of urea to form a polymer-like, glassy phase, which acts as the starting product for further conversions. Just by heating this phase it was possible to prepare either molybdenum and tungsten nitrides or carbides simply by changing the metal precursor/urea molar ratio. In this procedure, urea plays a double role as a nitrogen/carbon source and stabilizing agent (necessary for the nanoparticle dispersion). Molybdenum and tungsten nitride and carbides synthesized are almost pure and highly crystalline. Sizes estimated by WAXS range around 20 and 4 nm in diameter for Mo and W nitrides or carbides, respectively. The specific surface area was found between 10 and 80 m2/g, depending on the metal and the initial ratio of metal precursor to urea. PMID:19367981

Giordano, Cristina; Erpen, Christian; Yao, Weitang; Antonietti, Markus

2008-12-01

5

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

Microsoft Academic Search

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°C and completed within a short period of time. XRD spectrum of the combustion product reveals

M. Biswas; K.. Prabhakaran; N. M. Gokhale; S. C. Sharma

2007-01-01

6

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

7

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

8

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

9

Application of urea based SNCR system in the combustion effluent containing low level of baseline nitric oxide.  

PubMed

Selective Non-Catalytic Reduction (SNCR) of nitric oxide has been studied experimentally by injecting aqueous urea solution with and without additive in a pilot-scale diesel fired tunnel furnace at 3.4% excess oxygen level and with low ppm of baseline NO(x) ranging from 65 to 75 ppm within the investigated temperature range. The tests have been carried out using commercial grade urea as NO(x) reducing agent and commercial grade sodium carbonate as additive. The furnace simulated the small-scale combustion systems, where the operating temperatures are usually in the range of about 973 to 1323 K and NO(x) emission level remains below 100 ppm. With 5% plain urea solution, at Normalized Stoichiometric Ratio (NSR) of 4 as much as 54% reduction was achieved at 1128 K, whilst in the additive case the NO(x) reduction was improved to as much as 69% at 1093 K. Apart from this improvement, in the additive case, the effective temperature window as well as peak temperature of NO(x) reduction shifted towards lower temperatures. The result is quite significant, especially for this investigated level of baseline NO(x). The ammonia slip measurements showed that in both cases the slip was below 16 ppm at NSR of 4 and optimum temperature of NO(x) reduction. Finally, the investigations demonstrated that urea based SNCR is quite applicable to small-scale combustion applications and commercial grade sodium carbonate is a potential additive. PMID:15881021

Hossain, K A; Mohd-Jaafar, M N; Appalanidu, K B; Mustafa, A; Ani, F N

2005-03-01

10

Urea metabolism in plants.  

PubMed

Urea is a plant metabolite derived either from root uptake or from catabolism of arginine by arginase. In agriculture, urea is intensively used as a nitrogen fertilizer. Urea nitrogen enters the plant either directly, or in the form of ammonium or nitrate after urea degradation by soil microbes. In recent years various molecular players of plant urea metabolism have been investigated: active and passive urea transporters, the nickel metalloenzyme urease catalyzing the hydrolysis of urea, and three urease accessory proteins involved in the complex activation of urease. The degradation of ureides derived from purine breakdown has long been discussed as a possible additional metabolic source for urea, but an enzymatic route for the complete hydrolysis of ureides without a urea intermediate has recently been described for Arabidopsis thaliana. This review focuses on the proteins involved in plant urea metabolism and the metabolic sources of urea but also addresses open questions regarding plant urea metabolism in a physiological and agricultural context. The contribution of plant urea uptake and metabolism to fertilizer urea usage in crop production is still not investigated although globally more than half of all nitrogen fertilizer is applied to crops in the form of urea. Nitrogen use efficiency in crop production is generally well below 50% resulting in economical losses and creating ecological problems like groundwater pollution and emission of nitric oxides that can damage the ozone layer and function as greenhouse gasses. Biotechnological approaches to improve fertilizer urea usage bear the potential to increase crop nitrogen use efficiency. PMID:21421389

Witte, Claus-Peter

2010-12-01

11

Effect of urea and glycine fuels on the combustion reaction synthesis of Mn–Zn ferrites: Evaluation of morphology and magnetic properties  

Microsoft Academic Search

The goal of this study is to evaluate the influence of the urea and glycine fuels on the synthesis of Mn–Zn ferrite by combustion reaction. The morphology and magnetic properties of the resulting powders were investigated. The powders were characterized by X-ray diffraction (XRD), nitrogen adsorption (BET), scanning and transmission electron microscopy (SEM and TEM), and magnetic measurement of M×H

A. C. F. M. Costa; V. J. Silva; C. C. Xin; D. A. Vieira; D. R. Cornejo; R. H. G. A. Kiminami

2010-01-01

12

Modified solution combustion route for the preparation of plasma sprayable ceria powder  

Microsoft Academic Search

Plasma sprayable grade ceria powder was prepared by the solution combustion method. This is the first report on the application of solution combustion for the synthesis of plasma sprayable grade oxide powders. The fuels and fuel ratios used in the solution combustion were modified to achieve adequate flowability. It was found that when a mixture of fuels like glycine and

S. T. Aruna; K. S. Rajam

2009-01-01

13

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

SciTech Connect

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

Payette, R. [Ohio Dept. of Transportation, Jacksontown, OH (United States). District 5; Chen, X.Y.; Wolfe, W. [Ohio State Univ., Columbus, OH (United States); Beeghly, J. [Dravo Lime Co., Pittsburgh, PA (United States)

1995-12-31

14

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

15

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

NASA Astrophysics Data System (ADS)

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

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

2012-05-01

16

Nano crystalline ceria-neodymia solid solutions by combustion route: effect of agglomeration on powder properties.  

PubMed

About 8 compositions in the system Ce(1-x)Nd(x)O(2-x/2) (0.0 < or = x < or = 0.50) were prepared by the combustion process using glycine as a fuel and corresponding metal nitrates as the oxidants. The oxidant-to-fuel ratio was taken as 1:1.0. The products were characterized by X-ray diffraction (XRD), surface area, scanning electron microscopy (SEM), transmission electron microscopy (TEM), dynamic light scattering, sinterability etc. The crystallite size of powders, as obtained by the line broadening method, was typically in the range of 7 to 16 nm. The deagglomeration studies carried out showed that the average agglomerate size of these powders increases with increasing content of Nd in CeO2. The powders were sintered at 1200 degrees C to yield densities in the range of 80-95% of theoretical densities. This wide variation in the sintered density was explained based on the powder properties. An interesting observation was that the nature and size of the agglomerates plays an important role in governing properties such as sintered density and in turn ionic conductivity of nano ceramics. PMID:18019152

Bedekar, Vinila; Tyagi, A K

2007-09-01

17

Combustion synthesis of Ga 2 O 3 nanoparticles  

Microsoft Academic Search

Nanophase of Ga2O3 has potentially important applications in photocatalysis. We report the synthesis of nanophase of the metastable ?- and stable\\u000a ?-Ga2O3 and demonstrate that it is possible to prepare a continuously varying mixture starting from the pure metastable ?- to the\\u000a pure ?-phase. This is achieved by employing a facile and reliable combustion route, using urea as a fuel.

V. Srihari; V. Sridharan; H. K. Sahu; G. Raghavan; V. S. Sastry; C. S. Sundar

2009-01-01

18

Investigation of structural and luminescence properties of Ho3+ doped YAlO3 nanophosphors synthesized through solution combustion route  

NASA Astrophysics Data System (ADS)

YAlO3:Ho3+ (1-5 mol%) 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 (˜30 nm). The direct energy band gap (Eg) values estimated from Tauc's relation were found to be in the range 5.76-5.99 eV. Photoluminescence (PL) studies show green (540 and 548 nm) and red (645 and 742 nm) emissions upon excited at 452 nm wavelength. The emission peaks at ˜742 and 645 nm was associated with the transitions of 5F4 ? 5I7 and 5F5 ? 5I8 respectively. The higher energy bands located at 540 and 548 nm were associated with 5F4, 5S2 ? 5I8 transitions. Thermoluminescence (TL) studies of ?-irradiated YAlO3:Ho3+ (1-5 mol%) show two glow peaks at 223 and 325 °C recorded at a heating rate of 2.5 °C s-1. The 223 °C glow peak follow linear behavior up to 1 kGy and after that, it showed sub-linearity. Up to 1 kGy, 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.

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

19

Combustion  

NSDL National Science Digital Library

In this chemistry activity, learners discover that the weight of the product of combustion is greater than that of the starting material. Learners will compare the weight of steel wool before and after it is heated. Learners are asked to consider why the steel wool weighs more (oxidation) as well as write the balanced chemical equation for the burning of steel. This activity uses an open flame; adult supervision is recommended. The resource includes notes for educators and extension ideas.

House, The S.

2013-05-15

20

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

21

Facile Combustion Route for Low-Temperature Preparation of Sr2SiO4:Eu2+ Phosphor and Its Photoluminescence Properties  

NASA Astrophysics Data System (ADS)

Uniform and nanosized phosphors of Sr2SiO4:Eu2+ were successfully synthesized by a simple, inexpensive, and relatively low-temperature synthesis route using the combustion method. Through the chemical reaction of Sr(NO3)2, Eu(NO3)3, and fumed silica, the pure phase of nanosized Sr2SiO4:Eu2+ was obtained by sintering at 800 °C for 3 min. The crystallinity and morphology of the as-synthesized Sr2SiO4:Eu2+ powders were characterized by X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The particle size of the Sr2SiO4:Eu2+ powders was distributed in a range of 30-50 nm. Furthermore, their photoluminescence and luminescence decay properties were also systemically discussed and compared with those of Sr2SiO4:Eu2+ phosphor prepared by a conventional high-temperature solid-state reaction method. The luminescence decay curves indicated that the distribution of Eu2+ ions in the nanosized Sr2SiO4 powders was in a nearly homogeneous average local environment.

Lei, Bingfu; Machida, Ken-ichi; Horikawa, Takashi; Hanzawa, Hiromasa

2010-09-01

22

Detection of Interstellar Urea  

Microsoft Academic Search

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

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

2010-01-01

23

Combustion synthesis: a new route for repair of gas turbine components—principles and metallurgical structure in the NiAl\\/RBD61\\/superalloy junction  

Microsoft Academic Search

A new technique for repairing turbine blade materials based on combustion synthesis is described in this article. This process uses a local internal generation of heat provided by the NiAl combustion synthesis in order to rebuild damaged turbine components. In this study, a nickel base braze was inserted between a substrate of nickel base superalloy and a powders compact (Ni+Al).

C Pascal; R. M Marin-Ayral; J. C Tédenac; C Merlet

2003-01-01

24

Synthesis of nanosized bismuth ferrite (BiFeO 3 ) by a combustion method starting from Fe(NO 3 ) 3 ·9H 2 OBi(NO 3 ) 3 ·9H 2 O-glycine or urea systems  

Microsoft Academic Search

Two bismuth ferrite potential precursors systems, namely Fe(NO3)3·9H2O-Bi(NO3)3·9H2O-glycine\\/urea with different metal nitrate\\/organic compound molar ratios have been investigated in order to evaluate their\\u000a suitability as BiFeO3 precursors. The presence into the precursor of both reducing (glycine and urea) and oxidizing (NO3?) components, modifies dramatically their thermal behaviour comparative with the raw materials, both from the decomposition\\u000a stoichiometries and temperature occurrence

Carmen Paraschiv; B. Jurca; Adelina Ianculescu; Oana Carp

2008-01-01

25

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

NASA Astrophysics Data System (ADS)

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

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

2010-02-01

26

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)

1997-01-01

27

Urea Process Analytical Study.  

National Technical Information Service (NTIS)

In an effort to help determine the feasibility of the Urea process for production of the amine fuels, AFRPL established an in-house program to develop a useful analytical technique for monitoring the critical DMU to UDMH reaction. It was the absence of su...

L. A. Dee S. G. Wax

1976-01-01

28

Iron-stabilized nanocrystalline ZrO{sub 2} solid solutions: Synthesis by combustion and thermal stability  

SciTech Connect

The synthesis of Fe{sup 3+}-stabilized zirconia by the nitrate/urea combustion route was investigated. Using several characterization techniques, including X-ray diffraction, field-emission-gun scanning electron microscopy and notably Moessbauer spectroscopy, it was possible to determine the appropriate amount of urea that allows to obtain a totally stabilized Zr{sub 0.9}Fe{sub 0.1}O{sub 1.95} solid solution. The nanocrystalline zirconia solid solution is mostly tetragonal, but the presence of the cubic phase could not be ruled out. An in-depth study of the thermal stability in air showed that the Fe{sup 3+} solubility in the stabilized solid solution starts to decrease at about 875 deg. C which results in the formation of hematite (possibly containing some Zr{sup 4+}) at the surface of the zirconia grains and further provokes the progressive transformation into the monoclinic zirconia phase.

Legorreta Garcia, Felipe [Universite de Toulouse, CIRIMAT, CNRS-UPS-INP, Universite Paul-Sabatier, 31062 Toulouse cedex 9 (France); Resende, Valdirene Gonzaga de; De Grave, Eddy [NUMAT, Department of Subatomic and Radiation Physics, University of Ghent, Proeftuinstraat 86, B-9000 Gent (Belgium); Peigney, Alain; Barnabe, Antoine [Universite de Toulouse, CIRIMAT, CNRS-UPS-INP, Universite Paul-Sabatier, 31062 Toulouse cedex 9 (France); Laurent, Christophe, E-mail: laurent@chimie.ups-tlse.fr [Universite de Toulouse, CIRIMAT, CNRS-UPS-INP, Universite Paul-Sabatier, 31062 Toulouse cedex 9 (France)

2009-06-03

29

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.

30

The shape of urea  

Microsoft Academic Search

The shape of the urea molecule has been studied by analysing the microwave spectra of several isotopic species, yielding rs coordinates of all atoms except that of C, the latter being derived from first-moment equations, and by ab initio molecular-orbital calculations at the MP26-311++G(d,p) level. The derived bond lengths and angles are: r(CO), 1.221 Å; r(CN), 1.378 Å; r(NH(5)), 0.998

Peter D. Godfrey; Ronald D. Brown; Andrew N. Hunter

1997-01-01

31

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

32

Urea kinetic modeling for CRRT  

Microsoft Academic Search

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

Laurie Garred; Martine Leblanc; Bernard Canaud

1997-01-01

33

Pretreatment with Urea-Hydrochloric Acid Enhances the Isolation of Helicobacter pylori from Contaminated Specimens  

Microsoft Academic Search

Human saliva seeded with H. pylori was incubated in urea-HCl and then cultured on nonselective media. Pretreatment with 0.06 N HCl-0.08 M urea for 5 min at 37°C resulted in reproducible isolation of H. pylori, even at low inocula (<102 CFU\\/ml of saliva), despite the presence of large numbers of contaminating organisms. The transmission route and source of Helicobacter pylori

QUNSHENG SONG; GERALD W. ZIRNSTEIN; BALA SWAMINATHAN; BENJAMIN D. GOLD

2001-01-01

34

Urea transport in the kidney.  

PubMed

Urea transport proteins were initially proposed to exist in the kidney in the late 1980s when studies of urea permeability revealed values in excess of those predicted by simple lipid-phase diffusion and paracellular transport. Less than a decade later, the first urea transporter was cloned. Currently, the SLC14A family of urea transporters contains two major subgroups: SLC14A1, the UT-B urea transporter originally isolated from erythrocytes; and SLC14A2, the UT-A group with six distinct isoforms described to date. In the kidney, UT-A1 and UT-A3 are found in the inner medullary collecting duct; UT-A2 is located in the thin descending limb, and UT-B is located primarily in the descending vasa recta; all are glycoproteins. These transporters are crucial to the kidney's ability to concentrate urine. UT-A1 and UT-A3 are acutely regulated by vasopressin. UT-A1 has also been shown to be regulated by hypertonicity, angiotensin II, and oxytocin. Acute regulation of these transporters is through phosphorylation. Both UT-A1 and UT-A3 rapidly accumulate in the plasma membrane in response to stimulation by vasopressin or hypertonicity. Long-term regulation involves altering protein abundance in response to changes in hydration status, low protein diets, adrenal steroids, sustained diuresis, or antidiuresis. Urea transporters have been studied using animal models of disease including diabetes mellitus, lithium intoxication, hypertension, and nephrotoxic drug responses. Exciting new animal models are being developed to study these transporters and search for active urea transporters. Here we introduce urea and describe the current knowledge of the urea transporter proteins, their regulation, and their role in the kidney. PMID:23737200

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

2011-04-01

35

Evaporation of urea at atmospheric pressure.  

PubMed

Aqueous urea solution is widely used as reducing agent in the selective catalytic reduction of NO(x) (SCR). Because reports of urea vapor at atmospheric pressure are rare, gaseous urea is usually neglected in computational models used for designing SCR systems. In this study, urea evaporation was investigated under flow reactor conditions, and a Fourier transform infrared (FTIR) spectrum of gaseous urea was recorded at atmospheric pressure for the first time. The spectrum was compared to literature data under vacuum conditions and with theoretical spectra of monomolecular and dimeric urea in the gas phase calculated with the density functional theory (DFT) method. Comparison of the spectra indicates that urea vapor is in the monomolecular form at atmospheric pressure. The measured vapor pressure of urea agrees with the thermodynamic data obtained under vacuum reported in the literature. Our results indicate that considering gaseous urea will improve the computational modeling of urea SCR systems. PMID:21381736

Bernhard, Andreas M; Czekaj, Izabela; Elsener, Martin; Wokaun, Alexander; Kröcher, Oliver

2011-03-07

36

Studies on Eu doped Ba and Zn aluminate phosphors prepared by combustion synthesis  

NASA Astrophysics Data System (ADS)

BaAl2O4:Eu2+ and ZnAl2O4:Eu3+ phosphors were prepared by urea combustion route. The formation of crystalline aluminates was confirmed by X-ray diffraction. The X-band EPR spectra of BaAl2O4:Eu2+ showed the presence of Eu2+ ions, while in the case of ZnAl2O4:Eu3+, no signal attributable to Eu2+ was observed. The broad band UV excited luminescence of BaAl2O4:Eu2+ was observed at the blue region (?max = 439 nm) due to transitions from the 4f65d1 to the 4f7 configuration of the Eu2+ ion, whereas ZnAl2O4:Eu3+ gave an emission at 613 nm attributed to 5D0 7F2 transition of Eu3+ ions.

Singh, Vijay; Natarajan, V.; Zhu, Jun-Jie

2007-07-01

37

Combustion leftovers  

Microsoft Academic Search

Combustion processes almost never completely exhaust all of the available fuel. In this paper, we will consider three combustion scenarios (back-to-back premixed flames in stagnation point flow, travelling combustion waves, and microgravity spherical flame balls) and show how to calculate the amount of fuel which will be left over no matter how long we allow the combustion processes to continue.

R. O Weber; G. N Mercer; H. S Sidhu

2002-01-01

38

Mural Routes  

NSDL National Science Digital Library

Mural Routes is an organization dedicated to mural art which started in Toronto, Canada as a public art project in 1990. Its mission is to promote "wall art as a public art form for the general benefit of communities and artists." The Mural Routes website is considered to be the most comprehensive resource on murals on the web. Visitors will find a great interactive map of the murals across Canada on the "Mural Map of Canada" link, they will also find the route of "photographic ambassador" John Hands who has documented hundreds of outdoor murals across Canada. Visitors shouldn't miss the many murals located in Montreal, Quebec, especially "Diversitree", "Winter Haze" and "Rush of Fall". Many of the murals in Montreal emphasize its ethnic diversity and openness to newcomers. Mural Routes even gives visitors the opportunity to get their mural projects listed on the map, by clicking on the link, at the bottom of the page, next to the caricature of John Hands. Visitors interested in murals outside of Canada should click on the "International Murals" tab, to find links to murals in seven other countries, including Greece, Australia, and the United States.

39

Effect of urea supplemented and urea treated straw based diet on milk urea concentration in crossbred Karan-Fries cows  

Microsoft Academic Search

The study was undertaken to evaluate the effect of urea supplemented and urea treated straw based diet on milk urea concentration. Six multiparous crossbred Karan-Fries (Holstein Friesian ? Tharparkar) cows were blocked into three groups of nearly equal body weight, DIM, milk yield and milk fat content and were randomized into a 3 ? 3 Latin square design with 3-week

Arindam Dhali; Ram Kumar Mehla; Sunil Kumar Sirohi

2010-01-01

40

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

41

Critique of Adaptive Routing.  

National Technical Information Service (NTIS)

This report refutes claims is that adaptive routing performs better than dimension-order routing. Simulation results are presented that show dimension-order routing achieves both higher throughput and lower latency than adaptive routing. Specious claims f...

M. J. Pertel

1992-01-01

42

Triiodothyronine Administration Affects urea Synthesis in Rats  

Microsoft Academic Search

ABSTRACT The purpose of the present study was,to elucidate the mechanism,by which,thyroid hormone alters urea synthesis. The relative importance of urea cycle enzyme activities, substrate levels or the levels of urea cycle intermediates on urea production was investi gated in a set of four experiments in which rats were fed a diet supplemented with 6-propyl-2-thiouracil (PTU, a thyroid inhibitor) and

Kazotoshi Hayase; Goro Yonekawa; Akira Yoshida

43

Granulation of Urea in a Pan Granulator  

Microsoft Academic Search

Urea granulation is favored over prilling due to the problems associated with prilling. Tumbling agglomeration technique is employed in pan granulator. Product with wide size range can be produced by playing with only few parameters like binders (water and urea solution), ratio of binders, rpm of pan, granulation time and angle of inclination. Urea granulation is studied at laboratory scale

U. Irshad; M. N. Sharif; R. U. Khan; Z. H. Rizvi

44

Combustion engineering  

SciTech Connect

This book is an introduction to combustion science. It discusses general aspects of combustion processes and deals with combustion of premixed mixtures and covers basic concepts of flame propagation, including the flame structure, burning velocity, flame stability, and the Rankine-Hugoniot equations. The book also deals with diffusive combustion, covering laminar and turbulent diffusion flames. Explosions and detonations, including ideal and nonideal explosions, and detonation wave structure are addressed. The determination of the burned gas states is discussed.

Ohtake, K.; Fujiwara, T.

1985-01-01

45

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

46

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

47

How does urea really denature myoglobin?  

NASA Astrophysics Data System (ADS)

This study reports on a model for denaturation of myoglobin by urea for concentrations ranging from 0.1 M to 15 M. The experimental data from quartz crystal microbalance (QCM), circular dichroism (CD) and dilational rheology are examined with respect to a 'structure-breaking effect' of urea on the aqueous phase. Even at urea concentrations >10 M, native conformation of the protein is retained through a restabilization of the hydrophobic association. Our study shows that any proposed denaturation mechanism of large biomolecules requires very high concentrations of urea and the association of urea with protein-water system is based on enhancement of hydrophobic interactions.

Muthuselvi, L.; Miller, Reinhard; Dhathathreyan, A.

2008-11-01

48

Ontogeny of rabbit proximal tubule urea permeability.  

PubMed

Urea transport in the proximal tubule is passive and is dependent on the epithelial permeability. The present study examined the maturation of urea permeability (P(urea)) in in vitro perfused proximal convoluted tubules (PCT) and basolateral membrane vesicles (BLMV) from rabbit renal cortex. Urea transport was lower in neonatal than adult PCT at both 37 and 25 degrees C. The PCT P(urea) was also lower in the neonates than the adults (37 degrees C: 45.4 +/- 10.8 vs. 88.5 +/- 15.2 x 10(-6) cm/s, P < 0.05; 25 degrees C: 28.5 +/- 6.9 vs. 55.3 +/- 10.4 x 10(-6) cm/s; P < 0.05). The activation energy for PCT P(urea) was not different between the neonatal and adult groups. BLMV P(urea) was determined by measuring vesicle shrinkage, due to efflux of urea, using a stop-flow instrument. Neonatal BLMV P(urea) was not different from adult BLMV P(urea) at 37 degrees C [1.14 +/- 0.05 x 10(-6) vs. 1.25 +/- 0.05 x 10(-6) cm/s; P = not significant (NS)] or 25 degrees C (0.94 +/- 0.06 vs. 1.05 +/- 0.10 x 10(-6) cm/s; P = NS). There was no effect of 250 microM phloretin, an inhibitor of the urea transporter, on P(urea) in either adult or neonatal BLMV. The activation energy for urea diffusion was also identical in the neonatal and adult BLMV. These findings in the BLMV are in contrast to the brush-border membrane vesicles (BBMV) where we have previously demonstrated that urea transport is lower in the neonate than the adult. Urea transport is lower in the neonatal proximal tubule than the adult. This is due to a lower rate of apical membrane urea transport, whereas basolateral urea transport is the same in neonates and adults. The lower P(urea) in neonatal proximal tubules may play a role in overall urea excretion and in developing and maintaining a high medullary urea concentration and thus in the ability to concentrate the urine during renal maturation. PMID:11353675

Quigley, R; Lisec, A; Baum, M

2001-06-01

49

Aquaporin-9 and urea transporter-A gene deletions affect urea transmembrane passage in murine hepatocytes.  

PubMed

In mammals, the majority of nitrogen from protein degradation is disposed of as urea. Several studies have partly characterized expression of urea transporters (UTs) in hepatocytes, where urea is produced. Nevertheless, the contribution of these proteins to hepatocyte urea permeability (P(urea)) and their role in liver physiology remains unknown. The purpose of this study was to biophysically examine hepatocyte urea transport. We hypothesized that the water, glycerol, and urea channel aquaporin-9 (AQP9) is involved in hepatocyte urea release. Stopped-flow light-scattering measurements determined that the urea channel inhibitors phloretin and dimethylurea reduced urea permeability of hepatocyte basolateral membranes by 70 and 40%, respectively. In basolateral membranes isolated from AQP9(-/-) and UT-A1/3(-/-) single-knockout and AQP9(-/-):UT-A1/3(-/-) double-knockout mice, P(urea) was decreased by 30, 40, and 76%, respectively, compared with AQP9(+/-):UT-A1/3(+/-) mice. However, expression analysis by RT-PCR did not identify known UT-A transcripts in liver. High-protein diet followed by 24-h fasting affected the concentrations of urea and ammonium ions in AQP9(-/-) mouse liver and plasma without generating an apparent tissue-to-plasma urea gradient. We conclude that AQP9 and unidentified UT-A urea channels constitute primary but redundant urea facilitators in murine hepatocytes. PMID:23042941

Jelen, Sabina; Gena, Patrizia; Lebeck, Janne; Rojek, Aleksandra; Praetorius, Jeppe; Frøkiaer, Jørgen; Fenton, Robert A; Nielsen, Søren; Calamita, Giuseppe; Rützler, Michael

2012-10-04

50

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)

1999-01-01

51

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

52

Computational Combustion  

SciTech Connect

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

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

2004-08-26

53

Combustion heater  

Microsoft Academic Search

A wood burning combustion heater comprises a combustion chamber for long logs arranged to burn down from one end to the other in cigar-like fashion, an after-burner tube arrayed above and essentially parallel to the elongated logs with the air and burned gasses following an S-shaped path through the combustion chamber and out through the exhaust tube, an after-burner within

Kalenian

1980-01-01

54

Urea Transformation of Wetland Microbial Communities  

Microsoft Academic Search

Transformation of urea to ammonium is an important link in the nitrogen cycle in soil and water. Although microbial nitrogen\\u000a transformations, such as nitrification and denitrification, are well studied in freshwater sediment and epiphytic biofilm\\u000a in shallow waters, information about urea transformation in these environments is scarce. In this study, urea transformation\\u000a of sedimentary, planktonic, and epiphytic microbial communities was

Ann-Karin Thorén

2007-01-01

55

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

PubMed

The Chinese soft-shelled turtle, Pelodiscus sinensis, is well adapted to aquatic environments, including brackish swamps and marshes. It is ureotelic, and occasionally submerges its head into puddles of water during emersion, presumably for buccopharyngeal respiration. This study was undertaken to test the hypothesis that the buccophyaryngeal cavity constitutes an important excretory route for urea in P. sinensis. Results indicate that a major portion of urea was excreted through the mouth instead of the kidney during immersion. When restrained on land, P. sinensis occasionally submerged their head into water (20-100 min), during which urea excretion and oxygen extraction occurred simultaneously. These results indicate for the first time that buccopharyngeal villiform processes (BVP) and rhythmic pharyngeal movements were involved in urea excretion in P. sinensis. Urea excretion through the mouth was sensitive to phloretin inhibition, indicating the involvement of urea transporters (UTs). In addition, saliva samples collected from the buccopharyngeal surfaces of P. sinensis injected intraperitoneally with saline contained ~36 mmol N l(-1) urea, significantly higher than that (~2.4 mmol N l(-1)) in the plasma. After intraperitoneal injection with 20 ?mol urea g(-1) turtle, the concentration of urea in the saliva collected from the BVP increased to an extraordinarily high level of ~614 ?mol N ml(-1), but the urea concentration (~45 ?mol N ml(-1)) in the plasma was much lower, indicating that the buccopharyngeal epithelium of P. sinensis was capable of active urea transport. Subsequently, we obtained from the buccopharyngeal epithelium of P. sinensis the full cDNA sequence of a putative UT, whose deduced amino acid sequence had ~70% similarity with human and mouse UT-A2. This UT was not expressed in the kidney, corroborating the proposition that the kidney had only a minor role in urea excretion in P. sinensis. As UT-A2 is known to be a facilitative urea transporter, it is logical to deduce that it was localized in the basolateral membrane of the buccopharyngeal epithelium, and that another type of primary or secondary active urea transporter yet to be identified was present in the apical membrane. The ability to excrete urea through the mouth instead of the kidney might have facilitated the ability of P. sinensis and other soft-shelled turtles to successfully invade the brackish and/or marine environment. PMID:23053366

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

2012-11-01

56

Substituted Ureas. Methods of Synthesis and Applications  

NASA Astrophysics Data System (ADS)

Systematic data on the method of synthesis of ureas by the interaction of compounds containing the amino-group with organic isocyanates, of amines and alkyl halides with alkali metal cyanates, and of primary and secondary amines with phosgene, carbon dioxide, urea, or nitrourea and by the carbonylation of amines are presented. The reactions involving the alkylation of urea and its interaction with various compounds containing functional groups are considered. The advantages and disadvantages of various methods are noted. The principal and practical applications of substituted ureas, including their applications as additives to organic materials, are discussed. The bibliography includes 314 references.

Vishnyakova, T. P.; Golubeva, I. A.; Glebova, E. V.

1985-03-01

57

Rapid urea broth test for yeasts.  

PubMed Central

A rapid, miniaturized, urea broth test useful for detecting urease activity of yeasts was compared to Christensen urea agar. All urease-producing yeasts tested were positive on both media; however, 60% were reactive in the urea R broth within 30 min, and the remainder were reactive within 4 h. This urea multiwell test may be useful as a rapid screening method for detecting urease-producing yeasts recovered from clinical specimens and as an adjunct test with other rapid methods of yeast identification. Images

Roberts, G D; Horstmeier, C D; Land, G A; Foxworth, J H

1978-01-01

58

Urea-acetylene dicarboxylic acid reaction: A likely pathway for prebiotic uracil formation  

NASA Astrophysics Data System (ADS)

A number of routes have been suggested for the prebiotic synthesis of uracil involving the reaction of urea with malic acid, propiolic acid, cyanoacetylene and others. Cyanoacetylene has been detected in the interstellar medium as well as simulated prebiotic experiments. It is therefore plausible that dicyanoacetylene and its hydrolytic product acetylene dicarboxylic acid, (ADCA) may have played a role in chemical evolution. This aspect has been examined in the present work for the synthesis of uracil from ADCA and urea reaction. It was found that when ADCA reacted with urea, uracil was formed only in the presence of phosphoric acid and phosphates. Ammonium phosphates gave higher yields of uracil than other phosphates. In the absence of phosphoric acid or phosphates no uracil formation took place. This type of synthesis could have taken place in prebiotic oceans which contained ammonium phosphates and other salts.

Subbaraman, A. S.; Kazi, Z. A.; Choughuley, A. S. U.; Chadha, M. S.

1980-12-01

59

Urea-acetylene dicarboxylic acid reaction: a likely pathway for prebiotic uracil formation.  

PubMed

A number of routes have been suggested for the prebiotic synthesis of uracil involving the reaction of urea with malic acid, propiolic acid, cyanoacetylene and others. Cyanoacetylene has been detected in the interstellar medium as well as simulated prebiotic experiments. It is therefore plausible that dicyanoacetylene and its hydrolytic product acetylene dicarboxylic acid (ADCA) may have played a role in chemical evolution. This aspect has been examined in the present work for the synthesis of uracil from ADCA and urea reaction. It was found that when ADCA reacted with urea, uracil was formed only in the presence of phosphoric acid and phosphates. ammonium phosphates gave higher yields of uracil than other phosphates. In the absence of phosphoric acid or phosphates no uracil formation took place. This type of synthesis could have taken place in prebiotic oceans which contained ammonium phosphates and other salts. PMID:7454254

Subbaraman, A S; Kazi, Z A; Choughuley, A S; Chadha, M S

1980-12-01

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

Combustion process  

SciTech Connect

A combustion catalyst containing both manganese and antimony in a temperature range of above about 1260/sup 0/ F. has been found to result in unexpactedly high CO/sub 2//CO ratios in the regenerator off-gas when CO is combusted.

McKay, D.L.

1984-07-03

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

A technique for predicting urea release from coated urea in wetland soil  

Microsoft Academic Search

A simple technique for measuring urea release from different coated urea fertilizer materials in simulated wetland soil has been developed and tested. The laboratory soil system used simulates physical, chemical, and microbiological environments of wetland soils under field conditions. Laboratory and field values for urea release are in good agreement.

N. K. Savant; J. R. Clemmons; A. F. James

1982-01-01

64

Urea in rainwater and atmospheric aerosol  

NASA Astrophysics Data System (ADS)

The measurement of urea (CO(NH 2) 2) in rainwater samples from predominantly marine-influenced locations in Bermuda, and Ireland, and in rains and aqueous aerosol extracts from a rural site at UEA, Norwich indicates that urea is not generally a major contributor to atmospheric water-soluble organic nitrogen. At UEA, where anthropogenic and natural sources of urea are expected to be most intense, urea accounts for <10% of rainwater dissolved organic nitrogen (DON), and <1% of the water-soluble fraction of aerosol organic nitrogen. The analysis of size-segregated aerosol samples indicates that the size distribution of urea is quite different from those of ammonium and nitrate. In the less anthropogenically impacted Atlantic sites, rainwater urea was below the detection limits of the colorimetric method used in this study, consistent with expected dilution processes or reaction of urea during transport. However, in a small set of rain samples collected in Tahiti, urea concentrations ranged from 1 to 8 ?mol l -1, accounting for >40% of the DON measured in those samples. This may be a consequence of strong local sources, or it could possibly result from the partial breakdown of other DON compounds to urea during sample transport and storage. However, the similarity in urea concentrations observed in Pacific samples in this present study and in a previous one ( Timperley et al., 1985, Canadian Journal of Fisheries and Aquatic Science42, 1171-1177) suggests that this may reflect a difference in rain chemistry between Atlantic and Pacific rains, perhaps resulting from differences in levels of agricultural urea usage between Asia and the rest of the world.

Cornell, S. E.; Jickells, T. D.; Thornton, C. A.

65

Combustion synthesis of gadolinia doped ceria powder  

Microsoft Academic Search

Gadolinia doped ceria (GDC) powders with different gadolinia content in the range 0–15mol% were prepared by solution combustion route using a solution of cerium nitrate, gadolinium nitrate and citric acid. In the experiments citric acid to metal nitrate molar ratio was taken as 5:6. The solution on heating formed gel before combustion. Thermal analysis of the gel precursors containing different

T. Mahata; G. Das; R. K. Mishra; B. P. Sharma

2005-01-01

66

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

67

Automated analytical biosystem for urea monitoring  

Microsoft Academic Search

The present work describes the construction and automation of a flow injection (FI) system for on-line monitoring of urea. The FI system comprises a nylon column on the wall of which the enzyme urease is covalently immobilized. Urea is hydrolyzed to ammonium and hydrogen carbonate ions in the presence of urease. The final measurement is done by an ammonium ion

M. Jurkiewicz; M. Del Valle; S. Alegret; E. Martínez-Fábregas

1996-01-01

68

Competitive Online Multicommodity Routing  

Microsoft Academic Search

In this paper we study online multicommodity routing prob- lems in networks, in which commodities have to be routed sequentially. The flow of each commodity can be split on several paths. Arcs are equipped with load dependent price functions defining routing costs, which have to be minimized. We discuss a greedy online algorithm that routes each commodity by minimizing a

Tobias Harks; Stefan Heinz; Marc E. Pfetsch

2006-01-01

69

76 FR 15339 - Solid Urea From Russia and Ukraine  

Federal Register 2010, 2011, 2012, 2013

...Review)] Solid Urea From Russia and Ukraine AGENCY: United States International Trade...duty orders on solid urea from Russia and Ukraine...duty orders on solid urea from Russia and Ukraine would be likely to lead to...

2011-03-21

70

75 FR 74746 - Solid Urea From Russia and Ukraine  

Federal Register 2010, 2011, 2012, 2013

...Review)] Solid Urea From Russia and Ukraine AGENCY: United States International Trade...duty orders on solid urea from Russia and Ukraine...duty orders on solid urea from Russia and Ukraine would be likely to lead to...

2010-12-01

71

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

NASA Astrophysics Data System (ADS)

Urea nitrate (UN) is an explosive used in improvised explosive devices. UN (CH5N2O+NO3-) can be synthesized from readily available chemicals and was the main explosive used in the 1993 bombing of the World Trade Center. Isotopic analysis of this explosive has the potential to elucidate the isotopic ratios of the starting materials and geographic information on the location of synthesis. However, depending on the synthesis of the explosive, variable amounts of residual nitric acid may remain, yielding differing contributions of the components to the bulk UN ?15N values. Since ?15N nitrate values cannot be extrapolated from a single component and the bulk value, it is critical to separate the explosive into urea° and potassium nitrate. Therefore, we developed a method to isolate the components of UN for isotopic analysis through the neutralization of urea and separation via methanol washes. The urea in the explosive is neutralized with a 1.1:1 mole ratio of potassium hydroxide:urea in water resulting in urea° and potassium nitrate. The solution is then dried and the urea and potassium nitrate are separated using methanol. Urea and nitrate were isolated from samples of pre-blast UN and the completeness of the extraction was confirmed with a urease assay and a nitrate detection assay on the appropriate components. Isotopic analysis of the isolated urea and potassium nitrate were performed using an EA-IRMS, with the addition of sucrose to the potassium nitrate to aid combustion. For samples of relatively pure UN, the bulk UN ?15N value is stoichiometrically equivalent to the measured ?15N values of the isolated urea and nitrate in a 2:1 ratio. However, some explosive samples contained an excess of nitric acid due to poor preparation. As a result, the bulk UN ?15N values were biased towards the ?15N value of the nitrate. We are conducting experiments to compare the isotopic values of the initial starting reactants in the UN synthesis and the isotopic composition of the end products in order to test the forensic utility for linking the starting reactants to recovered UN. We are also investigating the extent of oxygen isotope exchange of nitrate and water during UN synthesis. This may provide constraints on the location of UN production, which will be useful in a forensic investigation.

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

2008-12-01

72

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)

2000-01-01

73

Combustion systems  

SciTech Connect

This patent describes an external combustion engine such as a Stirling engine and the like, having an external heat system housing in which is defined a heater space, a hollow liner formed of a ceramic material disposed in the heater space and defining a combustion chamber. Biasing means are coupled to a first end of the liner and coupled with the housing so as to maintain the liner in the heater space while dampening transmission of vibration in the housing to the liner.

Kralick, J.

1986-03-04

74

Hydrothermal synthesis of Mg-Al hydrotalcites by urea hydrolysis  

SciTech Connect

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

Rao, M. Mohan [Indian Institute of Chemical Technology, Inorganic Chemistry Division, Uppal Road, Hyderabad 500007 (India)]. E-mail: mandapati@iict.res.in; Reddy, B. Ramachandra [Indian Institute of Chemical Technology, Inorganic Chemistry Division, Uppal Road, Hyderabad 500007 (India); Jayalakshmi, M. [Indian Institute of Chemical Technology, Inorganic Chemistry Division, Uppal Road, Hyderabad 500007 (India); Jaya, V. Swarna [Indian Institute of Chemical Technology, Inorganic Chemistry Division, Uppal Road, Hyderabad 500007 (India); Sridhar, B. [Indian Institute of Chemical Technology, Inorganic Chemistry Division, Uppal Road, Hyderabad 500007 (India)

2005-02-15

75

Impact of urea on detergent micelle properties.  

PubMed

Co-solvents, such as urea, can entail drastic changes in the micellization behavior of detergents. We present a systematic quantification of the impact of urea on the critical micellar concentration, the micellization thermodynamics, and the micelle size in three homologous series of commonly used non-ionic alkyl detergents. To this end, we performed demicellization experiments by isothermal titration calorimetry and hydrodynamic size measurements by dynamic light scattering on alkyl maltopyranosides, cyclohexyl alkyl maltopyranosides, and alkyl glucopyranosides at urea concentrations of 0-8 M. For all detergents studied, we found that the critical micellar concentration increases exponentially because the absolute Gibbs free energy of micellization decreases linearly over the entire urea concentration range, as does the micelle size. In contrast, the enthalpic and entropic contributions to micellization reveal more complex, nonlinear dependences on urea concentration. Both free energy and size changes are more pronounced for long-chain detergents, which bury more apolar surface area upon micelle formation. The Gibbs free energy increments per methylene group within each detergent series depend on urea concentration in a linear fashion, although they result from the entropic term for alkyl maltosides but are of enthalpic origin for cyclohexyl alkyl maltosides. We compare our results to transfer free energies of amino acid side chains, relate them to protein-folding data, and discuss how urea-induced changes in detergent micelle properties affect in vitro investigations on membrane proteins. PMID:23745835

Broecker, Jana; Keller, Sandro

2013-06-24

76

Triiodothyronine administration affects urea synthesis in rats.  

PubMed

The purpose of the present study was to elucidate the mechanism by which thyroid hormone alters urea synthesis. The relative importance of urea cycle enzyme activities, substrate levels or the levels of urea cycle intermediates on urea production was investigated in a set of four experiments in which rats were fed a diet supplemented with 6-propyl-2-thiouracil (PTU, a thyroid inhibitor) and treated with triiodothyronine (T3). Compared with that of normal or control rats, the plasma level of T3 was significantly lower in rats fed a diet containing PTU only and elevated in rats given PTU + T3. Urinary excretion of urea and the liver content of ornithine in rats given PTU + T3 were significantly lower than in rats given PTU only. The liver level of ornithine was closely correlated to the excretion of urea in the present study. Fractional rates of protein synthesis in liver, kidney and small intestine were lower in the hypothyroid group. However, most free amino acid concentrations, except ornithine in liver and plasma and the activity of hepatic argininosuccinate synthetase (EC 6.3.4.5) of hypothyroid rats, were significantly reduced as compared with those of control or hyperthyroid rats. The results indicate that the increased hepatic ornithine content in the hypothyroid rats may be one of the regulatory factors causing changes in urea synthesis. PMID:2051240

Hayase, K; Yonekawa, G; Yokogoshi, H; Yoshida, A

1991-07-01

77

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

PubMed

The objective of this study was to examine the effects of 6 days of emersion on nitrogen metabolism and excretion in the Chinese soft-shelled turtle, Pelodiscus sinensis. Despite having a soft shell with a cutaneous surface that is known to be water permeable, P. sinensis lost only ~2% of body mass and was able to maintain its hematocrit and plasma osmolality, [Na(+)] and [Cl(-)] during 6 days of emersion. During emersion, it ameliorated water loss by reducing urine output, which led to a reduction (by 29-76%) in ammonia excretion. In comparison, there was a more prominent reduction (by 82-99%) in urea excretion during emersion due to a lack of water to flush the buccopharyngeal epithelium, which is known to be the major route of urea excretion. Consequently, emersion resulted in an apparent shift from ureotely to ammonotely in P. sinensis. Although urea concentration increased in several tissues, the excess urea accumulated could only account for 13-22% of the deficit in urea excretion. Hence, it can be concluded that a decrease (~80%) in urea synthesis occurred in P. sinensis during the 6 days of emersion. Indeed, emersion led to significant decreases in the activity of some ornithine-urea cycle enzymes (argininosuccinate synthetase/argininosuccinate lyase and arginase) from the liver of P. sinensis. As a decrease in urea synthesis occurred without the accumulation of ammonia and total free amino acids, it can be deduced that ammonia production through amino acid catabolism was suppressed with a proportional reduction in proteolysis in P. sinensis during emersion. Indeed, calculated results revealed that there could be a prominent decrease (~88%) in ammonia production in turtles after 6 days of emersion. In summary, despite being ureogenic and ureotelic in water, P. sinensis adopted a reduction in ammonia production, instead of increased urea synthesis, as the major strategy to ameliorate ammonia toxicity and problems associated with dehydration during terrestrial exposure. PMID:23348951

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

2013-01-24

78

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

79

Urea release from silicate- and polymer-coated urea in water and a simulated wetland soil  

Microsoft Academic Search

Urea release rates in water (38°C) and in a simulated wetland soil system under greenhouse conditions from silicate- and polymer-coated urea (SPCU) materials have been studied. The SPCU materials were prepared by the Korea Advanced Institute of Science and Technology (KAIST), Seoul, Korea, in cooperation with the International Fertilizer Development Center (IFDC). Average urea release (\\u000a$$\\\\overline {UR} $$\\u000a)

NK Savant; AF James; GH McClellan

1983-01-01

80

Urea reduction ratio that considers effects of ultrafiltration and intradialytic urea generation  

Microsoft Academic Search

We modified the urea reduction ratio (URR) equation to correct the effects of ultrafiltration and intradialytic urea generation on the delivered dose of hemodialysis: muRR = 1?R1+2?UFBW+0.01?t×100% where mURR is modified URR, R is postdialysis plasma urea nitrogen (PUN) to predialysis PUN ratio, UF is ultrafiltrate volume in liters, BW is postdialysis body weight in kilograms, and t is dialysis

Yuk Lun Cheng; Koon Shing Choi; Ka Foon Chau; Chun Sang Li; Cheen Unn Yung; Alex W Yu; Kwan Keung Wong

2001-01-01

81

Proxies for Anonymous Routing.  

National Technical Information Service (NTIS)

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 applic...

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

1996-01-01

82

Routing problems: A bibliography  

Microsoft Academic Search

This bibliography contains 500 references on four classical routing problems: the Traveling Salesman Problem, the Vehicle Routing Problem, the Chinese Postman Problem, and the Rural Postman Problem. References are presented alphabetically under a number of subheadings.

Gilbert Laporte; Ibrahim H. Osman

1995-01-01

83

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

2013-01-04

84

Neurological implications of urea cycle disorders  

Microsoft Academic Search

Summary  The urea cycle disorders constitute a group of rare congenital disorders caused by a deficiency of the enzymes or transport\\u000a proteins required to remove ammonia from the body. Via a series of biochemical steps, nitrogen, the waste product of protein\\u000a metabolism, is removed from the blood and converted into urea. A consequence of these disorders is hyperammonaemia, resulting\\u000a in central

A. L. Gropman; M. Summar; J. V. Leonard

2007-01-01

85

Detection of Interstellar Urea with Carma  

Microsoft Academic Search

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

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

2010-01-01

86

Reversible denaturation of cyclosporin synthetase by urea  

Microsoft Academic Search

The reversible denaturation of the multifunctional polypeptide, cyclosporin synthetase, by urea was analyzed. It is possible to discriminate between at least two stages of enzyme denaturation. While at low urea concentration (up to 0.8 M) cyclosporin A formation is inhibited, synthesis of the diketopiperazine cyclo-(d-alanyl-N-methylleucyl), a molecule representing a partial sequence of cyclosporin A is still detectable. At higher concentrations

Joachim Dittmann; François Vaillant; Horst Kleinkauf; Alfons Lawen

1996-01-01

87

Ammonia and Urea Permeability of Mammalian Aquaporins  

Microsoft Academic Search

The humanaquaporins,AQP3,AQP7, AQP8,AQP9, and possibly AQP10, are permeable to ammonia, and AQP7, AQP9, and possibly AQP3,\\u000a are permeable to urea. In humans, these aquaporins supplement the ammonia transport of the Rhesus (Rh) proteins and the urea\\u000a transporters (UTs). The mechanism by which ammonium is transported by aquaporins is not fully resolved. A comparison of transport\\u000a equations, models, and experimental data

Thomas Litman; Rikke Søgaard; Thomas Zeuthen

88

Influence of urea on polyvinyl alcohol molecular superstructure formation  

NASA Astrophysics Data System (ADS)

Whiskers up to 1 cm in length were grown in polyvinyl alcohol (PVA) and urea solution. Raman and IR spectra discover an interaction between PVA and urea molecules. Optical and electronic microscopy data show that urea influences on PVA molecular superstructure formation. PVA whiskers prepared in urea solution can be used for organic semiconductors production which properties are determined by arrangement of polymer macromolecules.

Prosanov, I. Yu.; Matvienko, A. A.; Bokhonov, B. B.

2011-06-01

89

Reduction of NOx emissions from a dry process preheater kiln with calciner through the use of the urea based SNCR process  

Microsoft Academic Search

The post combustion reduction of NOx using urea has proven to be an effective method in controlling NOx from various combustion sources. Such a reduction process has been successfully demonstrated in a week-long test at Ash Grove's dry process cement kiln system located in Seattle. This system is equipped with planetary coolers, a 5-stage preheater and an air-through-the-kiln calciner, Testing

H. E. Steuch; J. Hille; W. H. Sun; M. J. Bisnett; D. K. Kirk

1995-01-01

90

Reduction of NOx emissions from a dry process preheater kiln with calciner through the use of the urea-based SNCR process  

Microsoft Academic Search

The post combustion reduction of NOx using urea has proven to be an effective method in controlling NOx from various combustion sources, such a reduction process has been successfully demonstrated in a week-long test at Ash Grove's dry process cement kiln system located in Seattle. This system is equipped with planetary coolers, a 5-stage preheater and an air-through-the-kiln calciner. Testing

Hans E. Steuch; Jon T. Hille; William H. Sun; Michael J. Bisnett; Douglas W. Kirk

1996-01-01

91

Toward Compact Interdomain Routing  

Microsoft Academic Search

Despite prevailing concerns that the current Internet inte r- domain routing system will not scale to meet the needs of the 21st century global Internet, networking research has not yet led to the construction of a new routing architecture wit h satisfactory and mathematically provable scalability cha rac- teristics. Worse, continuing empirical trends of the exist - ing routing and

Dmitri V. Krioukov; Kimberly C. Claffy

2005-01-01

92

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

93

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

94

3. VIEW WEST, ROUTE 130 SOUTH FROM ROUTE 30 EAST ...  

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

3. VIEW WEST, ROUTE 130 SOUTH FROM ROUTE 30 EAST ISLAND - White Horse Pike Rond Point, Intersection of Crescent Boulevard (U.S. Route 130), White Horse Pike (U.S. Route 30), & Clay Avenue, Collingswood, Camden County, NJ

95

12. VIEW EAST, ROUTE 30 EAST FROM ROUTE 130 SOUTH ...  

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

12. VIEW EAST, ROUTE 30 EAST FROM ROUTE 130 SOUTH ISLAND - White Horse Pike Rond Point, Intersection of Crescent Boulevard (U.S. Route 130), White Horse Pike (U.S. Route 30), & Clay Avenue, Collingswood, Camden County, NJ

96

1. VIEW NORTH, ROUTE 130 NORTH FROM ROUTE 30 EAST ...  

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

1. VIEW NORTH, ROUTE 130 NORTH FROM ROUTE 30 EAST ISLAND - White Horse Pike Rond Point, Intersection of Crescent Boulevard (U.S. Route 130), White Horse Pike (U.S. Route 30), & Clay Avenue, Collingswood, Camden County, NJ

97

4. VIEW SOUTH, ROUTE 30 EAST FROM ROUTE 130 NORTH ...  

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

4. VIEW SOUTH, ROUTE 30 EAST FROM ROUTE 130 NORTH ISLAND - White Horse Pike Rond Point, Intersection of Crescent Boulevard (U.S. Route 130), White Horse Pike (U.S. Route 30), & Clay Avenue, Collingswood, Camden County, NJ

98

2. VIEW SOUTHEAST, ROUTE 30 EAST FROM ROUTE 30 EAST ...  

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

2. VIEW SOUTHEAST, ROUTE 30 EAST FROM ROUTE 30 EAST ISLAND - White Horse Pike Rond Point, Intersection of Crescent Boulevard (U.S. Route 130), White Horse Pike (U.S. Route 30), & Clay Avenue, Collingswood, Camden County, NJ

99

13. VIEW SOUTH, ROUTE 130 SOUTH FROM ROUTE 130 SOUTH ...  

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

13. VIEW SOUTH, ROUTE 130 SOUTH FROM ROUTE 130 SOUTH ISLAND - White Horse Pike Rond Point, Intersection of Crescent Boulevard (U.S. Route 130), White Horse Pike (U.S. Route 30), & Clay Avenue, Collingswood, Camden County, NJ

100

Stratified combustion type engine  

Microsoft Academic Search

The present invention relates to a stratified combustion type engine comprising an engine cylinder, a main combustion chamber located above the cylinder, an injection nozzle for injecting auxiliary fuel towards the combustion chamber, and an open pre-combustion chamber provided within the combustion chamber for locally holding and vaporizing the flow of auxiliary fuel from the injection nozzle. The pre-combustion chamber

Kamiya

1977-01-01

101

Stratified combustion type engine  

Microsoft Academic Search

A stratified combustion type engine is described that is comprised of an engine cylinder, a main combustion chamber located above the cylinder, an injection nozzle for injecting auxiliary fuel towards the combustion chamber, and an open pre-combustion chamber provided within the combustion chamber for locally holding and vaporizing the flow of auxiliary fuel from the injection nozzle. The pre-combustion chamber

Kamiya

1978-01-01

102

Routing hazardous materials shipments  

SciTech Connect

The people who live or work near highways may be endangered by accidents which involve releases of hazardous materials. This dissertation examines two routing criteria to determine if either can reduce the threat to society from hazardous-materials releases occurring in transport. The two criteria are: routes that minimize the total length of shipment, minimizing the probability of accidents, and, routes that minimize the size of the population brought into contact with the shipment so that in the event of an accident the number of people potentially exposed to the danger are minimized. Linear programming is used to find 105 pairs of routes between 210 randomly selected points on the United States Interstate Highway System. The length and population size of each route are used in a model of accident probabilities to estimate the size of the population potentially endangered on each route. The results of the model are tested to evaluate the differences in size of the endangered populations for each route type. Minimum-population routes significantly reduce the size of the population endangered, even though these routes are longer and experience a higher probability of accidents. Multiobjective programming is then applied to the problem in order to examine a wider range of routes. The routes found using this technique are compromise routes that do not minimize either population or length. The findings of this method indicate there are routes that can reduce the size of the endangered population but do not increase the length of route to the same extent as does the absolute minimum-population route.

Robbins, J.C.

1981-01-01

103

Disparity in properties of 20-mol% Eu-doped ceria synthesized by different routes  

Microsoft Academic Search

Ce0.8Eu0.2O2?? was synthesized by conventional solid state route as well as wet chemical route (i.e. cation complexation, combustion method). The crystallite size obtained for cation complexation and combustion samples is 14 and 19nm while their surface area is 11.70 and 29.63m2g?1 respectively. Cation complexation synthesized product lead to formation of agglomerates and hence the sintered sample showed porosity compared to

R. V. K. Wandekar; B. N. Wani; S. R. Bharadwaj

2010-01-01

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

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

106

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

107

Effects of Urea on M 4Lactate Dehydrogenase from Elasmobranchs and Urea-Accumulating Australian Desert Frogs  

Microsoft Academic Search

We measured the effect of urea on M4-lactate dehydrogenase (M4-LDH) from elasmobranchs and Australian desert frogs (urea accumulators) and from two animals that do not accumulate urea, the axolotl and the rabbit. An analysis of the effect of urea on the Kd(NADH), V, V\\/Km(pyr) and V\\/Km(NADH) shows that in all cases the major effect of urea was on the binding

Caroline J Fuery; Paul V Attwood; Philip C Withers; Paul H Yancey; John Baldwin; Michael Guppy

1997-01-01

108

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

109

Factors affecting N release of urea from reactive layer coated urea  

Microsoft Academic Search

An experimental fertilizer called reactive layer coated urea (RLCU) has been developed by coating urea with a mixture of diisocyanate and polyol in the presence of a catalyst. The hard, durable layer that is formed on the granule conveys slow-release character to the product. A series of soil incubation tests were conducted under simulated upland conditions for periods up to

C. B. Christianson

1988-01-01

110

Transfer of Pasteurella ureae Jones 1962 to the Genus Actinobacillus Brumpt 1910: Actinobacillus ureae comb. nov  

Microsoft Academic Search

By using the renaturation method for deoxyribonucleic acid (DNA)-DNA hybridization (2), we have found that the species Pasteurella ureae consists of strains that are inter- related at DNA binding levels of more than 90% and that this species is confined to human hosts (9). The species most closely related to P. ureae (as revealed by DNA binding, using the same

R. MUTTERS; S. POHL

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

Evolutionary aspects of urea utilization by fungi  

PubMed Central

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

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

2009-01-01

113

Regulation of Renal Urea Transport by Vasopressin  

PubMed Central

Terrestrial life would be miserable without the ability to concentrate urine. Production of concentrated urine requires complex interactions among the nephron segments and vasculature in the kidney medulla. In addition to water channels (aquaporins) and sodium transporters, urea transporters are critically important to the theories proposed to explain the physiologic processes occurring when urine is concentrated. Vasopressin (anti-diuretic hormone) is the key hormone regulating the production of concentrated urine. Vasopressin rapidly increases water and urea transport in the terminal inner medullary collecting duct (IMCD). Vasopressin rapidly increases urea permeability in the IMCD through increases in phosphorylation and apical plasma-membrane accumulation of the urea transporter A1 (UT-A1). Vasopressin acts through two cAMP-dependent signaling pathways in the IMCD: protein kinase A and exchange protein activated by cAMP Epac. Protein kinase A phosphorylates UT-A1 at serines 486 and 499. In summary, vasopressin regulates urea transport acutely by increasing UT-A1 phosphorylation and the apical plasma-membrane accumulation of UT-A1 through two cAMP-dependent pathways.

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

2011-01-01

114

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

115

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

116

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

117

Liquid fuel combustion apparatus  

Microsoft Academic Search

This patent describes a vaporized liquid fuel combustion apparatus of the type including: a cylinder defining a combustion chamber, the cylinder having an inlet end for receipt of combustion air and an outlet end for exhausting gaseous combustion products; an end plate covering the inlet end of the cylinder; a blower, including a rotor and a casing, for supplying combustion

K. Sawada; Y. Kimijima; H. Umehara

1986-01-01

118

Gas turbine combustion  

Microsoft Academic Search

This text focuses on the fundamentals of gas turbine combustion, emphasizing combustor design and performance. The material presented is based on the latest research results. Aerodynamic and heat transfer processes in gas turbine combustors as well as the combustion performance parameters of ignition, combustion efficiency, and stability are described. Some of the topics covered are combustion fundamentals; diffusers; aerodynamics; combustion

1983-01-01

119

Pulsating Combustion Device Miniaturization.  

National Technical Information Service (NTIS)

The phenomenon of pulsating combustion remains one of the least understood forms of combustion. In this thesis, combustion oscillations are classified into the categories of chamber oscillations, system oscillations, and intrinsic oscillations. Two pulsat...

R. K. Crowe

1976-01-01

120

Routing of Railway Carriages  

Microsoft Academic Search

In the context of organizing timetables for railway companies the following railway carriage routing problem occurs. Given a timetable containing rail links with departure and destination times\\/stations and the composition of the trains, find a routing of railway carriages such that the required carriages are always available when a train departs. The problem is formulated as an integer multi-commodity network

Peter Brucker; Johann Hurink; Thomas Rolfes

2003-01-01

121

Minimum crosstalk channel routing  

Microsoft Academic Search

As technology advances, interconnection wires are placed in closer proximitg and circuits operate at higher frequencies. Consequently, reduction of crosstalk-s between interconnection wires becomes an important consideration in VLSI design. In this paper, we study the gm’dded channel routing problem with the objective of satisfying crosstalk constraints for the nets. We propose a new approach which utilizes extstzng channel routing

Tong Gao; C. L. Liu

1993-01-01

122

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

123

MATHEMATICAL MODELLING OF UREA PRILLING PROCESS  

Microsoft Academic Search

A mathematical model is proposed for the urea prilling process of a commercial plant. In this model the prilling process has been simulated by simultaneous solution of the continuity, hydrodynamic, mass and energy transfer equations. Particle trajectory, temperature and moisture distribution of the particles and of the cooling air along the height of the tower was calculated from the mathematical

A. ALAMDARI; A. JAHANMIRI; N. RAHMANIYAN

2000-01-01

124

Distribution of Urea in the Baltic Sea.  

National Technical Information Service (NTIS)

The vertical distribution of urea has been determined during a five-year period (from June 1976 to May 1981) at 21 different stations in the Baltic Sea on samples collected during 20 cruises. Results show pronounced seasonal variations with the highest co...

J. C. Valderrama

1983-01-01

125

Urea-catalyzed construction of oxazinanes.  

PubMed

Highly functionalized oxazinanes are efficiently prepared through urea-catalyzed formal [3 + 3] cycloaddition reactions of nitrones and nitrocyclopropane carboxylates. The reaction system is general with respect to both the nitrocyclopropane carboxylates and nitrones enabling the preparation of a large family of oxazinanes, typically in high yield. This method affords access to enantioenriched oxazinane products through chirality transfer from enantioenriched nitrocyclopropane carboxylates. PMID:23907178

Hardman, Andrea M; So, Sonia S; Mattson, Anita E

2013-08-14

126

Foliar urea fertilization of cereals: A review  

Microsoft Academic Search

It has been suggested that there are several potential benefits of providing nitrogen to cereals via the foliage as urea solution. These include: reduced nitrogen losses through denitrification and leaching compared with nitrogen fertilizer applications to the soil; the ability to provide nitrogen when root activity is impaired e.g., in saline or dry conditions, and uptake late in the season

M. J. Gooding; W. P. Davies

1992-01-01

127

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.

128

Ad Hoc Routing  

NASA Astrophysics Data System (ADS)

Chapter 1 presented multi-hop communication as one of the opportunities to reduce the energy consumption of the devices, thus extending their lifetime. The development of efficient multi-hop routing protocols is therefore a fundamental aspect for the successful deployment of wireless ad hoc networks. However, routing in wireless ad hoc networks is fundamentally different from the apparently similar problem in wired networks, because bandwidth is scarce and topology changes frequently. This raises a double challenge for multi-hop routing in wireless ad hoc networks: nodes are less powerful and routing is more difficult. Given this fact, it is not surprising to observe that multi-hop routing has been one of the most active fields of research in MANETs.

Araujo, Filipe; Miranda, Hugo

129

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

PubMed

Molecular-dynamics (MD) simulations of urea crystals of different shapes (cubic, rectangular prismatic, and sheet) have been performed using our previously published force field for urea. This force field has been validated by calculating values for the cohesive energy, sublimation temperature, and melting point from the MD data. The cohesive energies computed from simulations of cubic and rectangular prismatic urea crystals in vacuo at 300 K agreed very well with the experimental sublimation enthalpies reported at 298 K. We also found very good agreement between the melting points as observed experimentally and from simulations. Annealing the crystals just below the melting point leads to reconstruction to form crystal faces that are consistent with experimental observations. The simulations reveal a melting mechanism that involves surface (corner/edge) melting well below the melting point, and rotational disordering of the urea molecules in the corner/edge regions of the crystal, which then facilitates the translational motion of these molecules. PMID:22281810

Özp?nar, Gül Alt?nba?; Beierlein, Frank R; Peukert, Wolfgang; Zahn, Dirk; Clark, Timothy

2012-01-27

130

DENATURATION CHANGES IN EGG ALBUMIN WITH UREA, RADIATION, AND HEAT  

PubMed Central

The extent of urea denaturation depends on the concentration of protein and urea and also on the temperature of the solution. Egg albumin solutions (0.9 per cent) are not denatured by 20 per cent urea, denature slowly with 25 per cent urea, and denature rapidly with 35 per cent urea at room temperature. At a higher temperature 30 per cent urea is rapidly effective. Denaturation of the egg albumin molecule by radiation or by heat is accompanied by structural changes as evidenced by optical rotation values, but is not accompanied by association or dissociation of the molecule in the pH range outside the zone in which aggregation follows denaturation. Denaturation of the egg albumin molecule by urea produces no change in optical rotation until the concentration of urea is high enough to dissociate the molecule. In the presence of urea a urea-protein complex is formed in which the protein is denatured but cannot flocculate because of the dispersive action of the urea. This prevents flocculation of proteins exposed to radiation and subsequent heating to 40° C. as the urea-protein complex is not broken down at a temperature of 40° C. The presence of urea therefore prevents the flocculation of proteins denatured by radiation. The urea-protein complex is broken down by heating to 55–58° C. so that the molecules aggregate at a temperature below the temperature of rapid heat denaturation. This appears to be an acceleration of heat denaturation or a lowering of the heat denaturation temperature, but in reality is an effect of heat on the urea-protein complex which frees the urea-denatured protein and permits its aggregation.

Clark, Janet H.

1943-01-01

131

Influence of urea on polyvinyl alcohol molecular superstructure formation  

Microsoft Academic Search

Whiskers up to 1 cm in length were grown in polyvinyl alcohol (PVA) and urea solution. Raman and IR spectra discover an interaction\\u000a between PVA and urea molecules. Optical and electronic microscopy data show that urea influences on PVA molecular superstructure\\u000a formation. PVA whiskers prepared in urea solution can be used for organic semiconductors production which properties are determined\\u000a by

I. Yu. Prosanov; A. A. Matvienko; B. B. Bokhonov

2011-01-01

132

Sensitive Specialization Analysis of Urea in Human Blood by Surface Acoustic Wave Urea Sensor System  

Microsoft Academic Search

A novel and sensitive enzymatic method for the determination of micro amounts of urea in human blood has been developed based on the surface acoustic wave (SAW) urea sensor system, which was prepared by combining a SAW device with urease (E.C. 3.5.1.5) extracted directly from watermelon seeds. The Michaelis constant and maximum rate of the urease were estimated as 1.77

Liu Dezhong; Ge Kai; Chen Kang; Nie Lihua; Yao Shouzhuo

1996-01-01

133

21 CFR 176.320 - Sodium nitrate-urea complex.  

Code of Federal Regulations, 2013 CFR

... 3 2013-04-01 2013-04-01 false Sodium nitrate-urea complex. 176.320 Section...Components of Paper and Paperboard § 176.320 Sodium nitrate-urea complex. Sodium nitrate-urea complex may be safely...

2013-04-01

134

Adaptation of Lactating Cows to Rations Containing Urea  

Microsoft Academic Search

Effects of a progressive change in 6 wk from a urea-free concentrate to one providing .34 (medium) or .66 g (high) urea\\/kg body weight on jugular blood composition and animal performance were studied with 27 cows. Consumption of dry matter was not affected even at the high rate of urea intake. Milk produc- tion was maximum when after 6 wk

P. R. Narasimhalu; R. J. Belzile; G. J. Brisson; W. B. Holtman

1980-01-01

135

76 FR 77015 - Solid Urea From Russia and Ukraine  

Federal Register 2010, 2011, 2012, 2013

...Review)] Solid Urea From Russia and Ukraine Determination On the basis of the record...duty orders on solid urea from Russia and Ukraine would be likely to lead to continuation...entitled Solid Urea from Russia and Ukraine: Investigation Nos. 731-TA-...

2011-12-09

136

MICROWAVE-ASSISTED PREPARATION OF CYCLIC UREAS FROM DIAMINES  

EPA Science Inventory

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

137

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

138

Selective inhibition of urea transport by oxidizing agents  

Microsoft Academic Search

Summary Urea and water transport across the toad bladder epithelial cell appears to take place through independent vasopressin-stimulated pathways. Agents such as chromate, for example, when added to the luminal bathing medium, inhibit urea transport without inhibiting osmotic water flow, providing evidence for such independent pathways. In the present study, selective inhibition of urea transport is shown for permanganate and

Nicholas Franki; Roland Einhorn; Richard M. Hays

1975-01-01

139

Assessment of dialysis adequacy using the dialysate urea monitor: preliminary experience of the dialysate urea monitor.  

PubMed

Numerous studies have identified a strong linkage between the delivered dialysis dose (Kt/V) and the survival of hemodialysis (HD) patients. However, the current method used to calculate Kt/V requires multiple blood samples and the process is complex and time consuming. We evaluate the performance of a recently developed on-line monitor (Biostat 1000 dialysate urea monitor, Baxter) that measures the urea concentration in the effluent dialysate and displays Kt/V and nPCR immediately after hemodialysis. To verify the performance of the urea monitor, we selected 21 hemodialysis patients, calculated their Kt/V and nPCR values from blood samples obtained during each hemodialysis, and compared the results with data obtained using the urea monitor. The Kt/V and nPCR values calculated by the urea monitor were both significantly correlated with those obtained using blood samples (R = 0.804, p < 0.001 in Kt/V and R = 0.749, p < 0.001 in nPCR). Our results suggest that the urea monitor may be used for on-line assessment of dialysis adequacy and obviates the need for blood sampling. PMID:9415936

Lee, W C; Tsai, C J; Huang, C C; Lee, C C; Chien, Y S; Hu, S A; Wu, C H

1997-11-01

140

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

141

Incentive-Compatible Interdomain Routing.  

National Technical Information Service (NTIS)

The routing of traffic between Internet domains, or Autonomous Systems (ASes), a task known as interdomain routing, is currently handled by the Border Gateway Protocol (BGP). Using BGP, autonomous systems can apply semantically rich routing policies to ch...

J. Feigenbaum M. Schapira V. Ramachandran

2006-01-01

142

Preparation of cadmium chromite spinel: a combustion approach  

Microsoft Academic Search

The effect of preparation precursors as well as the presence and\\/or the absence of a combustion fuel, viz. urea, on the texture of Cd–Cr–O system was investigated. The phase changes accompanying the thermal treatment of three Cd–Cr–O parents were monitored using thermogravimetry, differential scanning calorimetry, X-ray diffractometry and Fourier transform infrared spectroscopy. Moreover, the surface excess charge, Cr6+ ions, was

Bahaa Mohamed Abu-Zied

2002-01-01

143

Fluidized bed combustion method  

SciTech Connect

A process is described for fluidized bed combustion of particulate combustible material in a furnace comprising feeding the particulate combustible material to the furnace and imparting a turbulent fluidized bed motion to the particulate combustible material within the furnace through the use of a vibrating screen. The screen is connected to means for vibrating the screen as the principal source of energy for imparting the turbulent fluidizing motion to the combustible material. This feeds combustion air to the fluidized bed of combustible material, discharging products of combustion from the furnace, and causing the fluidized bed to move in substantially horizontal direction so that combustible material is conveyed from the location of feed to the furnace through a combustion stage in the furnace to the location of discharge as combustible products.

Love, R.E.

1986-12-16

144

Urea transformation and the adaptability of three leafy vegetables to urea as a source of nitrogen in hydroponic culture  

Microsoft Academic Search

Substitution of urea for commonly used nitrate fertilizers in hydroponic culture of vegetables would not only avoid excessive accumulation of nitrate in plants but would also reduce the cost of production. This substitution, however, might have adverse effects, such as a dramatic decrease in solution pH, reduced nutrient uptake and possibly urea toxicity per se. Differences in adaptability to urea

Jian Luo; Zhaohuang Lian; Xiaolong Yan

1993-01-01

145

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

146

Combustion apparatus  

US Patent & Trademark Office Database

A combustion apparatus 2 has a fuel spraying nozzle 12, a feed canal 16 and a return canal 17, both the canals connected to the nozzle, with the former canal 16 feeding a fuel to the nozzle and with the latter canal 17 allowing an unsprayed portion of the fuel to flow back. An electromagnetic pump 18 disposed in the feed canal 16 serves to compress the fuel towards the nozzle 12, and an injector valve 25 is disposed in the return canal 17. A controller 40 regulates the operation of the injector valve 25 in the manner of duty-ratio control so as to adjust the flow rate of the fuel being sprayed out of the nozzle 12.

2005-06-21

147

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

Microsoft Academic Search

The aims of this study were 1) to deter- mine whether transfer of blood urea to the gastrointes- tinal tract (GIT) or the efficiency of capture of urea N within the GIT is more limiting for urea N salvage, and 2) to establish the relationship between plasma urea concentration and recycling of urea N to the GIT. We used an

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

2006-01-01

148

Onion Routing Access Configurations.  

National Technical Information Service (NTIS)

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. Thus it hides not only the data being sent, but who is talking to...

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

2000-01-01

149

Liquid fuel combustion apparatus  

Microsoft Academic Search

A liquid fuel combustion apparatus is described comprising: wall means defining a cylindrical combustion chamber; a cylindrical portion of the wall means having a first port therein for receiving an ignition device and a first nipple integral with the wall means and surrounding the first port; means for introducing fuel and combustion air into the combustion chamber and for removing

K. Sawada; K. Kikuchi

1987-01-01

150

Thermal Pulse Combustion  

Microsoft Academic Search

This paper describes theoretical and experimental observations of combustion oscillations produced in a continuously mixed, jet-stirred combustion system. This work is distinct from other investigations of pulse combustion, because it is shown both theoretically and experimentally that combustion oscillations can be produced with a steady supply of fuel and air, requiring no mechanical or aerodynamic valves. The theory is a

G. A. RICHARDS; G. J. MORRIS; D. W. SHAW; S. A. KEELEY; M. J. WELTER

1993-01-01

151

Rotary internal combustion engine  

SciTech Connect

This patent describes an internal combustion engine comprising; a rotary compressor mechanism; a rotary expander mechanism; and combustion chamber means disposed between the compressor mechanism and the expander mechanism, whereby compressed air is delivered to the combustion chamber through the compressor discharge port, and pressurized gas is delivered from the combustion chamber into the expander mechanism through the pressurized gas intake port.

Le, L.K.

1990-11-20

152

Pulse combustion apparatus  

Microsoft Academic Search

A pulse combustion apparatus is described which includes: a combustion chamber; an exhaust system including an exhaust pipe forming a resonant system with the combustion chamber and a generally cylindrical exhaust cushion chamber downstream of the exhaust pipe for receiving combustion gases from the pipe and communicating with an exhaust outlet form the apparatus; means for delivering successive fuel charges

Kitchen

1986-01-01

153

Query Routing with Ants?  

Microsoft Academic Search

In this paper we propose SemAnt, a novel ant-based algo- rithm designed for query routing in taxonomy-based peer-to-peer envi- ronments. We introduce the reader to the pheronome trail-laying-and- following behaviour observed from natural ants and show how it can be applied to query routing in peer-to-peer networks. Our proposed algo- rithm accounts for network parameters such as bandwidth and latency

Elke Michlmayr; Sabine Graf; Wolf Siberski; Wolfgang Nejdl

154

Urea formaldehyde foam insulation: defusing a timebomb  

SciTech Connect

With the onset of the energy crisis in the 1970's, thousands of homeowners insulated their homes with Urea Formaldehyde Foam Insulation (UFFI). The discovery that UFFI releases formaldehyde, a carcinogen and irritant, prompted various state and federal responses to this problem. This Note reviews those responses and concludes that a ban on the sale of UFFI, coupled with a removal and repurchase program, is the most effective solution from the standpoint of consumer health.

Fox, E.M.

1985-01-01

155

Benzobisoxazole fluorophore vicariously senses amines, ureas, anions.  

PubMed

A benzobisoxazole-based cruciform fluorophore forms fluorescent complexes with simple boronic acids. Through the changes of their fluorescence emission colours, these complexes can sense and qualitatively distinguish among structurally similar organic nitrogen compounds (amines and ureas) and small organic and inorganic anions. Preliminary results suggest that the intensity of this hybrid sensor's fluorescent response to chloride anions can be quantitatively correlated to chloride concentration. PMID:22983092

Lim, Jaebum; Miljani?, Ognjen Š

2012-10-25

156

Urea Induced Denaturation of Pre-Q1 Riboswitch  

NASA Astrophysics Data System (ADS)

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

Yoon, Jeseong; Thirumalai, Devarajan; Hyeon, Changbong

2013-01-01

157

Urea-Induced Denaturation of PreQ1-Riboswitch.  

PubMed

Urea, a polar molecule with a large dipole moment, not only destabilizes folded RNA structures but can also enhance the folding rates of large ribozymes. Unlike the mechanism of urea-induced unfolding of proteins, which is well understood, the action of urea on RNA has barely been explored. We performed extensive all-atom molecular dynamics simulations to determine the molecular underpinnings of urea-induced RNA denaturation. Urea displays its denaturing power in both secondary and tertiary motifs of the riboswitch structure. Our simulations reveal that the denaturation of RNA structures is mainly driven by the hydrogen-bonding and stacking interactions of urea with the bases. Through detailed studies of the simulation trajectories, we found that geminate pairs between urea and bases due to hydrogen bonds and stacks persist only ?0.1-1 ns, which suggests that the urea-base interaction is highly dynamic. Most importantly, the early stage of base-pair disruption is triggered by penetration of water molecules into the hydrophobic domain between the RNA bases. The infiltration of water into the narrow space between base pairs is critical in increasing the accessibility of urea to transiently disrupted bases, thus allowing urea to displace inter-base hydrogen bonds. This mechanism-water-induced disruption of base pairs resulting in the formation of a "wet" destabilized RNA followed by solvation by urea-is the exact opposite of the two-stage denaturation of proteins by urea. In the latter case, initial urea penetration creates a dry globule, which is subsequently solvated by water, leading to global protein unfolding. Our work shows that the ability to interact with both water and polar or nonpolar components of nucleotides makes urea a powerful chemical denaturant for nucleic acids. PMID:23863126

Yoon, Jeseong; Thirumalai, D; Hyeon, Changbong

2013-07-31

158

8. VIEW NORTHEAST, ROUTE 130 NORTH FROM ROUTE 30 WEST ...  

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

8. VIEW NORTHEAST, ROUTE 130 NORTH FROM ROUTE 30 WEST FROM WOODLYNNE AVENUE ISLAND - White Horse Pike Rond Point, Intersection of Crescent Boulevard (U.S. Route 130), White Horse Pike (U.S. Route 30), & Clay Avenue, Collingswood, Camden County, NJ

159

1. Intersection of US Route 4 and NH Route 143, ...  

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

1. Intersection of US Route 4 and NH Route 143, showing farmhouse on left, barn at right. Looking east. - Batchelder-Edgerly Farmstead, Barn, U.S. Route 4, southwest side, southeast corner of New Hampshire Route 43, Northwood, Rockingham County, NH

160

Stability Aware Routing: Exploiting Transient Route Availability in MANETs  

Microsoft Academic Search

The highly dynamic character of a mobile ad-hoc network (MANET) poses signican t challenges on network communications and resource manage- ment. Previous work on routing in MANETs has resulted in numerous routing protocols that aim at satisfying constraints such as minimum hop\\/distance or low energy. Existing routing protocols often fail to discover stable routes be- tween source and sink when

Pramita Mitra; Christian Poellabauer; Shivajit Mohapatra

2007-01-01

161

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

162

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

163

Combustion 2000  

SciTech Connect

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

None

2000-06-30

164

Protein stabilization by urea and guanidine hydrochloride.  

PubMed

The urea, guanidine hydrochloride, salt, and temperature dependence of the rate of dissociation of CO from a nonequilibrium state of CO-bound native ferrocytochrome c has been studied at pH 7. The heme iron of ferrocytochrome c in the presence of denaturing concentrations of guanidine hydrochloride (GdnHCl) and urea prepared in 0.1 M phosphate, pH 7, binds CO. When the unfolded protein solution is diluted 101-fold into CO-free folding buffer, the protein chain refolds completely, leaving the CO molecule bonded to the heme iron. Subsequently, slow thermal dissociation of the CO molecule yields to the heme coordination of the native M80 ligand. Thus, the reaction monitors the rate of thermal conversion of the CO-liganded native ferrocytochrome c to the M80-liganded native protein. The rate of this reaction, k(diss), shows a characteristic dependence on the presence of nondenaturing concentrations of the denaturants in the reaction medium. The rate decreases by approximately 1.9-3-fold as the concentration of GdnHCl in the refolding medium increases from nearly 0 to approximately 2.1 M. Similarly, the rate decreases by 1.8-fold as the urea concentration is raised from 0.l to approximately 5 M. At still higher concentrations of the denaturants the denaturing effect sets in, the protein is destabilized, and hence the CO dissociation rate increases sharply. The activation energy of the reaction, E(a), increases when the denaturant concentration in the reaction medium is raised: from 24.1 to 28.3 kcal mol(-1) for a 0.05-2.1 M rise in GdnHCl and from 25.2 to 26.9 kcal mol(-1) for a 0.1-26.9 M increase in urea. Corresponding to these increases in denaturant concentrations are also increases in the activation entropy, S(diss)/R, where R is the gas constant of the reaction. The denaturant dependence of these kinetic and thermodynamic parameters of the CO dissociation reaction suggests that binding interactions with GdnHCl and urea can increase the structural and energetic stability of ferrocytochrome c up to the limit of the subdenaturing concentrations of the additives. NaCl and Na(2)SO(4), which stabilize proteins through their salting-in effect, also decrease the rate with a corresponding increase in activation entropy of CO dissociation from CO-bound native ferrocytochrome c, lending support to the view that low concentrations of GdnHCl and urea stabilize proteins. These results have direct relevance to the understanding and interpretation of the free energy-denaturant relationship and protein folding chevrons. PMID:12416983

Bhuyan, Abani K

2002-11-12

165

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

166

Reversible inhibition of urea exchange in rat hepatocytes.  

PubMed Central

Urea exchange is enhanced in renal collecting duct cells and erythrocytes by transporters which can be inhibited by phloretin and urea analogs such as thiourea. In this study, evidence for a comparable transporter was found in rat livers perfused with solutions which contained no red cells and in suspensions of hepatocytes. Bolus injections containing 125I-albumin (intravascular indicator), 99mTc-DTPA (extracellular indicator), 3HOH (water indicator), and [14C]urea were administered into the portal vein and fluid was collected from the hepatic vein. Under control conditions, [14C]urea and 3HOH emerged from the hepatic vein at nearly the same rate. However when the perfusate contained 2.5 mM phloretin (equivalent to 0.058 mM phloretin not bound to albumin), the amount of [14C]urea which had been recovered in the hepatic venous outflow by the time of peak 125I-albumin concentrations exceeded 3HOH recovery by a factor of 2.31 +/- 0.23 (n = 7). When the perfusate contained 200 mM thiourea, the comparable recovery of [14C]urea from the hepatic veins exceeded that of 3HOH by a factor of 3.48 +/- 0.44 (n = 7). These effects were at least partially reversible and suggested inhibition of urea transporters in hepatocytes. This conclusion was supported by studies of unloading of [14C]urea from hepatocytes which were exposed to unlabeled solutions: in the presence of phloretin, the amount of [14C]urea remaining within hepatocytes at 4 s was approximately twice that remaining in hepatocytes which had not been exposed to phloretin. Rapid transport of urea out of hepatocytes may increase urea synthesis and minimize cellular swelling due to urea accumulation.

Effros, R M; Jacobs, E; Hacker, A; Ozker, K; Murphy, C

1993-01-01

167

Multicompartment urea kinetics in well-dialyzed children  

Microsoft Academic Search

Multicompartment urea kinetics in well-dialyzed children.BackgroundWe have reported catch-up growth with hemodialysis (HD) of approximately 15 hours\\/week. Without an equilibrated post-treatment blood urea nitrogen, the variable-volume single-pool (VVSP) model will not account for urea rebound, inflating the estimated HD dose (Kdt\\/V). A two-pool model (FVDP) predicts rebound, but requires fixed compartment volumes for the equations to be solvable in closed

Atul Sharma; Pauline Espinosa; Lorraine Bell; Alex Tom; Celia Rodd

2000-01-01

168

Urea determination using pH–enzyme electrode  

Microsoft Academic Search

A pH-membrane electrode with n-tridodecylamine (TDDA) as the hydrogen-ion-selective ionophore was used for the construction of a potentiometric biosensor for urea determination. The electrode was enzymatically modified by covalent binding of urease molecules directly to the surface of the potentiometric membrane. Incorporation of the urea biosensor into simple double-channel flow injection analysis (FIA) system allows reproducible urea determination in a

Robert Koncki; Agnieszka Chudzik; Izabela Walcerz

1999-01-01

169

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

170

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

171

9. BUILDING NO. 424, ORDNANCE FACILITY (COMBUSTIBLE CARTRIDGE CASE FACTORY), ...  

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

9. BUILDING NO. 424, ORDNANCE FACILITY (COMBUSTIBLE CARTRIDGE CASE FACTORY), VIEW EAST LOOKING AT NORTHWEST AND SOUTHWEST FACADES. BUILDING NO. 427-A, MAGAZINE, IN LEFT BACKGROUND; BUILDING NO.S 424-E, MIX HOUSE, AND 424-D, MAGAZINE, IN RIGHT BACKGROUND. - Picatinny Arsenal, 400 Area, Gun Bag Loading District, State Route 15 near I-80, Dover, Morris County, NJ

172

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

PubMed

Following the identification of trisubstituted ureas as a promising new chemical series of allosteric modulators of the calcium sensing receptor (CaSR), we further explored the SAR around the urea substitution, leading to the discovery of benzothiazole urea compound 13. This compound is a potent calcimimetic with an EC50=20 nM (luciferase assay). Evaluated in an in vivo model of chronic renal failure (short term and long term in 5/6 nephrectomized rats), benzothiazole urea 13 significantly decreased PTH levels after oral administration while keeping calcemia within the normal range. PMID:23499504

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

2013-02-08

173

Combustion 2000  

SciTech Connect

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

None

1999-12-31

174

Combustive Sound Source.  

National Technical Information Service (NTIS)

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 mi...

P. S. Wilson

1994-01-01

175

Radiative Augmented Combustion.  

National Technical Information Service (NTIS)

Radiative Augmented Combustion has been identified as a potential technique for extending aircraft operating limits associated with combustion processes. This technique is based on the fact that radiation of selected wavelengths is capable of photodissoci...

M. Lavid

1984-01-01

176

Transient Spray Combustion Computations.  

National Technical Information Service (NTIS)

Many practical combustion devices involves direct injection of liquid fuel into the combustion chamber, e.g., gas turbine engines, diesel engines, rockets and ramjet engines, and furnaces. Typically, the fuel is of sufficiently low volatility that vaporiz...

W. A. Sirignano

1986-01-01

177

Opportunities in Pulse Combustion.  

National Technical Information Service (NTIS)

In pulse combustion, burning occurs in a tube in an oscillatory manner, in contrast to the steady-state combustion used in most boilers and furnaces. With the right combination of the combustor's dimensions, valve characteristics, fuel/oxidizer combinatio...

H. J. Bomelburg D. L. Brenchley

1985-01-01

178

Stories as Route Descriptions  

Microsoft Academic Search

While navigation instructions in terms of turn instructions and distances are suitable for guiding drivers on roads, a different context of use - like pedestrian navigation - requires extended routing data and algorithms as well as adapted presentation forms to be effective. In our work we study alternative forms of navigation instructions for pedestrians in city environments. In this paper

Volker Paelke; Birgit Elias

2007-01-01

179

BGP route reflection revisited  

Microsoft Academic Search

The original BGP design requires that all BGP speakers within an autonomous system be directly connected with each other to create a full mesh, and BGP update messages be propagated to directly connected neighbors only. This requirement leads to BGP session scalability problems in networks with large numbers of BGP routers. Route reflection was proposed as a quick fix to

Jong Park; Ricardo Oliveira; Shane Amante; Danny Mcpherson; Lixia Zhang

2012-01-01

180

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

181

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

182

Vaporized liquid fuel combustion apparatus  

Microsoft Academic Search

This patent describes a vaporized liquid fuel combustion apparatus comprising: a cylinder defining a combustion chamber, the cylinder having an inlet end for receipt of combustion air, a first flange surrounding the inlet end and an outlet end for exhausting gaseous combustion products; means for introducing the fuel into the combustion chamber and ignition means exposed to the combustion chamber

Y. Kimijima; K. Kikuchi

1986-01-01

183

Route oscillations in I-BGP with route reflection  

Microsoft Academic Search

We study the route oscillation problem [16, 19] in the Internal Border Gateway Protocol (I-BGP)[18] when route reflection is used. We propose a formal model of I-BGP and use it to show that even deciding whether an I-BGP configuration with route reflection can converge is an NP-Complete problem. We then propose a modification to I-BGP and show that route reflection

Anindya Basu; Chih-Hao Luke Ong; April Rasala; F. Bruce Shepherd; Gordon Wilfong

2002-01-01

184

A routing protocol and routing algorithm for space communication  

NASA Astrophysics Data System (ADS)

The proposed research is a development a routing protocol for space that creates an infrastructure which enables routers on board spacecrafts to calculate near optimum routing tables ahead of time and on-demand when network changes occur. Our routing protocol for space communication, Space Open Shortest Path First (SOSPF), divides the routing domain (e.g., our solar system) into areas within areas which provides an orderly fashion of transmitting routing information throughout the routing domain. The concept of areas within SOSPF allows routing information of one area to be hidden within that area. In addition, since the trajectory of space crafts are either predictable (e.g., satellite constellation around Earth), preset (e.g., the International Space Station), or set on demand (e.g., a space shuttle), a router on board those spacecrafts calculates the time intervals where spacecrafts are in direct view with the calculating router and the propagation delays to those spacecrafts using the location of those spacecrafts and the local transmission capabilities. Then, those calculated values are dispersed throughout the routing domain. Also, this dissertation presents a routing algorithm which allows routers on board spacecrafts to use the received routing information (i.e., the time intervals and the propagation delay) to compute the routing table. This routing algorithm can compute shortest delay paths over conventional concurrent-link as well as intermittent-links using a store-and-forward communication scheme. Furthermore, this dissertation presents routing performance of this routing protocol in real space scenarios and shows how the SOSPF routing domain stays stable after link failures as the routing domain diameter grows to the end of our solar system.

Bantan, Nouman

185

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

NASA Astrophysics Data System (ADS)

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

Banchorndhevakul, Siriwattana

2002-08-01

186

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

PubMed

Studies suggest that choline has potential to be used as a dietary supplement and a drug for immune inflammatory diseases like asthma and rhinitis. But there are apprehensions regarding adverse effects of choline when given orally in high doses. To address this knowledge gap, toxicity assessment of choline chloride was carried out by intranasal (i.n.), oral and intraperitoneal (i.p.) routes in Balb/c mice for 28days. Body weight, food and water consumption of mice were recorded daily. Hematology and clinical chemistry were assessed to check hepatocellular functions and morphological alterations of the cells. Splenocyte counts were analysed for evaluating cellular immunity. Liver function test was performed by assaying different enzyme systems in serum such as, urea, blood urea nitrogen (BUN), creatinine, alanine aminotransferase (ALT), and aspartate aminotransferase (AST). Body weight, food and water consumption did not differ between mice treated with choline and the saline control group. Hematologic and biochemical variables were not affected with any increase in serum toxicity marker enzymes indicating normal liver functioning. Choline administration did not affect total cholesterol and high density lipoprotein levels as compared to their respective controls. Urea and blood urea nitrogen levels in choline treated mice were not different than controls. Creatinine level was, however, higher than control in i.p. treatment group, but other parameters were normal. In conclusion, the repeated consumption of choline chloride via i.n. and oral or i.p. routes did not cause toxicity in mice in the toxicological endpoints examined. PMID:19460409

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

2009-05-19

187

Different fuels combustion burner  

Microsoft Academic Search

This patent describes a burner for simultaneous combustion of liquid and solid fuels comprising: a liquid-fuel combustion nozzle having a liquid fuel injection port for injecting liquid fuel into the burner circumferentially of the liquid fuel nozzle along an arc subtending a predetermined angle; and a solid-fuel combustion nozzle having a solid fuel injection port for injecting a solid fuel

S. Miyamae; T. Abe

1987-01-01

188

Combustion chamber noise suppressor  

Microsoft Academic Search

A combustion chamber is described for a hot fog generating machine comprising a hollow cylindrical combustion chamber shell having a closure plate at one end and outlet means at the opposite end for directing hot combustion gasses to a fogging nozzle, air inlet means disposed adjacent the outlet means, fuel inlet means and ignition means mounted in the closure plate

1986-01-01

189

Combustion synthesis and nanomaterials  

Microsoft Academic Search

The recent developments and trends in combustion science towards the synthesis of nanomaterials are discussed. Different modifications made to conventional combustion approaches for preparation of nanomaterials are critically analyzed. Special attention is paid to various applications of combustion synthesized nanosized products.

Singanahally T. Aruna; Alexander S. Mukasyan

2008-01-01

190

Weather routing in long-distance Mediterranean routes  

NASA Astrophysics Data System (ADS)

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

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

2010-10-01

191

Predicting Catastrophic BGP Routing Instabilities.  

National Technical Information Service (NTIS)

Inter-domain routing connects individual pieces of Internet topology, creating an integral, global data delivery infrastructure. Currently, this critical function is performed by the Border Gateway Protocol (BGP) version 4 RF01771. Like all routing protoc...

L. K. Nguyen

2004-01-01

192

Method of regulating combustion in the combustion chambers of an internal combustion engine  

SciTech Connect

A method is proposed for regulating the combustion of operating mixtures in the combustion chambers of internal combustion engines. The course of the light intensity of the light resulting from combustion in the combustion chamber is detected and evaluated over the course of combustion; reference control variables derived therefrom are formed for use by subsequently disposed closed-loop control devices of the engine.

Burkel, R.; Eckert, K.; Franke, H.; Linder, E.; Maurer, H.; Moser, W.; Muller, K.; Peter, C.; Rieger, F.

1983-05-03

193

Evidence that the Adverse Effect of Urea Fertilizer on Seed Germination in Soil is Due to Ammonia Formed through Hydrolysis of Urea by Soil Urease  

Microsoft Academic Search

Studies using seeds of wheat (Triticum aestivum L.), rye (Secale cereale L.), barley (Hordeum vulgare L.), and corn (Zea mays L.) indicated that the adverse effect of urea fertilizer on seed germination in soil is due to ammonia formed through hydrolysis of urea by soil urease and is not due to urea itself, to urea fertilizer impurities such as biuret,

John M. Bremner; Michael J. Krogmeier

1989-01-01

194

Nitrification and Anammox with Urea as the Energy Source  

Microsoft Academic Search

Urea is present in many ecosystems and can be used as an energy source by chemolithotrophic aerobic ammonia oxidizing bacteria (AOB). Thus the utilization of urea in comparison to ammonia, by AOB as well as anaerobic ammonia oxidizing (Anammox) bacteria was investigated, using enrichments cultures, inoculated with activated sludge, and molecular ecological methods. In batch enrichment cultures grown with ammonia

A. Olav Sliekers; Suzanne Haaijer; Markus Schmid; Harry Harhangi; Karin Verwegen; J. Gijs Kuenen; Mike S. M. Jetten

2004-01-01

195

Final report of the safety assessment of Urea.  

PubMed

Although Urea is officially described as a buffering agent, humectant, and skin-conditioning agent-humectant for use in cosmetic products, there is a report stating that Urea also is used in cosmetics for its desquamating and antimicrobial action. In 2001, the Food and Drug Administration (FDA) reported that Urea was used in 239 formulations. Concentrations of use for Urea ranged from 0.01% to 10%. Urea is generally recognized as safe by FDA for the following uses: side-seam cements for food contact; an inhibitor or stabilizer in pesticide formulations and formulations applied to animals; internal sizing for paper and paperboard and surface sizing and coating of paper and paper board that contact water-in-oil dairy emulsions, low-moisture fats and oils, moist bakery products, dry solids with surface containing no free fats or oil, and dry solids with the surface of fat or oil; and to facilitate fermentation of wine. Urea is the end product of mammalian protein metabolism and the chief nitrogenous compound of urine. Urea concentrations in muscle, liver, and fetuses of rats increased after a subcutaneous injection of Urea. Urea diffused readily through the placenta and into other maternal and fetal organs. The half-life of Urea injected into rabbits was on the order of several hours, and the reutilization rate was 32.2% to 88.8%. Urea given to rats by a bolus injection or continuous infusion resulted in distribution to the following brain regions: frontal lobe, caudate nucleus, hippocampus, thalamus plus hypothalamus, pons and white matter (corpus callosum). The permeability constant after treatment with Urea of whole skin and the dermis of rabbits was 2.37 +/- 0.13 (x 10(6)) and 1.20 +/- 0.09 (x10(3)) cm/min, respectively. The absorption of Urea across normal and abraded human skin was 9.5% +/- 2.3% and 67.9% +/- 5.6%, respectively. Urea increased the skin penetration of other compounds, including hydrocortisone. No toxicity was observed for Urea at levels as high as 2000 mg/kg in acute oral studies using female rats or mice. No signs of toxicity were observed in male piglets dosed orally with up to 4 g/kg Urea for 5 days. Dogs dosed orally with 5 to 30 g/L Urea for 4 to 10 days had signs of toxicity, including weakness, anorexia, vomiting and retching, diarrhea and a decreased body temperature, which led to a deep torpor or coma. No significant microscopic changes were observed in the skin of male nude mice dermally exposed to 100% Urea for 24 h. No observable effect on fetal development was seen in rats and mice dosed orally with an aqueous solution of Urea (2000 mg/kg) on days 10 and 12 of gestation. The mean number of implants, live fetuses, percent fetal resorptions, mean fetal weight, and percent fetuses malformed were comparable to control group. A detergent containing 15% Urea was injected into pregnant ICR-JCl mice and dams and fetuses had no significant differences when compared to control animals. Urea given orally did not enhance the developmental toxicity of N-nitrosomethylurea. Female Sprague-Dawley rats injected in the uterine horn with 0.05 ml Urea on day 3 (preimplantation) or on day 7 (post implantation) exhibited no maternal mortality or morbidity; a dose-dependent reduction in embryo survival was seen with preimplantation treatment. Urea injected intra-amniotically induces mid-trimester abortions in humans. Urea was not genotoxic in several bacterial and mammalian assays; although in assays where Urea was used at a high concentration, genotoxicity was found, many in in vitro assays. Urea is commonly used in studies of DNA because it causes uncoiling of DNA molecules. Urea was not carcinogenic in Fisher 344 rats or C57B1/6 mice fed diets containing up to 4.5% Urea. Exposure of normal human skin to 60% Urea produced no significant irritation in one study, but 5% Urea was slightly irritating and 20% Urea was irritating in other reports. Burning sensations are the most frequently reported effect of Urea used alone or with other agents in treatment of diseased skin. Overall, there are few reports of sensiti

2005-01-01

196

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

197

A structural basis for the interaction of urea with lysozyme.  

PubMed Central

The effect of urea on the crystal structure of hen egg-white lysozyme has been investigated using X-ray crystallography. High resolution structures have been determined from crystals grown in the presence of 0, 0.7, 2, 3, 4, and 5 M urea and from crystals soaked in 9 M urea. All the forms are essentially isomorphous with the native type II crystals, and the derived structures exhibit excellent geometry and RMS differences from ideality in bond distances and angles. Comparison of the urea complex structures with the native enzyme (type II form, at 1.5 A resolution) indicates that the effect of urea is minimal over the concentration range studied. The mean difference in backbone conformation between the native enzyme and its urea complexes varies from 0.18 to 0.49 A. Conformational changes are limited to flexible surface loops (Thr 69-Asn 74, Ser 100-Asn 103), the active site loop (Asn 59-Cys 80), and the C-terminus (Cys 127-Leu 129). Urea molecules are bound to distinct sites on the surface of the protein. One molecule is bound to the active site cleft's C subsite, at all concentrations, in a fashion analogous to that of the N-acetyl substituent of substrate and inhibitor sugars normally bound to this site. Occupation of this subsite by urea alone does not appear to induce the conformational changes associated with inhibitor binding.

Pike, A. C.; Acharya, K. R.

1994-01-01

198

Urinary Urea Nitrogen as an Indicator of Pregnancy Risk.  

National Technical Information Service (NTIS)

The purpose of this investigation was to assess the amount of protein in the diets of pregnant women as reflected by the urinary urea nitrogen/cretinine nitrogen (UN/CN) and urea nitrogen/total nitrogen (UN/TN) ratios and to relate protein intake to pregn...

F. J. Zlatnik

1982-01-01

199

Factors Associated with Milk Urea Concentrations in Ontario Dairy Cows  

Microsoft Academic Search

All DHI test-day data, including milk urea concentra- tions measured by infrared test method, were collected from 60 commercial Ontario Holstein dairy herds for a 13-mo period between December 1, 1995, and December 31, 1996. The objectives of this study were to describe the relationships between milk urea concentrations and seasonal factors, sampling factors, cow factors, and test- day production

S. M. Godden; K. D. Lissemore; D. F. Kelton; K. E. Leslie; J. S. Walton; J. H. Lumsden

2001-01-01

200

Routing in a cyclic mobispace  

Microsoft Academic Search

A key challenge of routing in delay tolerant networks (DTNs) is finding routes that have high delivery rates and low end- to-end delays. When oracles are not available for future connectivity, opportunistic routing is preferred in DTNs, in which messages are forwarded to nodes with higher delivery probabilities. We observe that real objects have repetitive motions, but no prior research

Cong Liu; Jie Wu

2008-01-01

201

Deflection routing in hypercube networks  

Microsoft Academic Search

An approximate analysis of the transient and steady state behavior of deflection routing in hypercube networks is presented, under a uniform traffic model. In deflection routing congestion causes packets admitted to the network to be temporarily misrouted rather than buffered or dropped. The approximations show that deflection routing performs remarkably well in hypercube networks, for small as well as large

Albert G. Greenberg; Bruce Hajek

1992-01-01

202

Fast printed circuit board routing  

Microsoft Academic Search

This paper describes the algorithms in a printed circuit board router used for fully automatic routing of high-density circuit boards. Completely automatic routing and running times of a few minutes have resulted from a new data structure for efficient representation of the routing grid, quick searches for optimal solutions, and generalizations of Lee's algorithm.

Jeremy Dion

1987-01-01

203

Compass routing on geometric networks  

Microsoft Academic Search

this paper we study local routing algorithms on geometric networks. Formally speaking, suppose that we want to travel from a vertex s to a vertex t of a geometric network. A routing algorithm is called a local routing algorithm if it satisfies the following conditions:

Evangelos Kranakis; Harvinder Singh; Jorge Urrutia

1999-01-01

204

Simultaneous Circuit Transformation and Routing  

Microsoft Academic Search

In this paper, we propose a new methodology to integrate circuit transformation into routing. More specifically, this paper shows an approach for performing routing and wire reconnection simultaneously. To accomplish this, we introduce a new logic representation that implements all possible wire reconnections implicitly by enhancing global flow optimization techniques. Since our method takes into account circuit transformation during routing

Hiroaki Yoshida; Motohiro Sera; Masao Kubo; Masahiro Fujita

2002-01-01

205

[Irreversible inactivation of Chlorella glutamine synthetase by urea].  

PubMed

The effect of urea on Chlorella glutamine synthetase (E. C. 6.3.1.2) activity and tertiary structure is investigated. Urea is found to inhibit the activity of glutamine synthetase, the inhibitory effect being independent on the time. The enzyme molecule relax and changes its affinity to ammonium under the effect of urea at concentrations of 1.0-4.0 M. Higher concentrations of urea (5,0 M and more) produce a dissociation of the enzyme molecule into monomers without any intermediate forms. Monomers do not possess any synthetase and transferase activities. Substrates and cofactors do not protect the enzyme from the effect of urea and do not stimulate the emzyme reactivation and reaggregation after its dissotiation. The data obtained are discussed from the viewpoint of the regulation of Chlorella glutamine synthetase activity in vivo. PMID:26431

Rasulov, A S; Evstigneeva, Z G; Kretovich, W L

1978-05-01

206

Brain swelling after dialysis: old urea or new osmoles?  

PubMed

The pathogenesis of brain swelling and neurological deterioration after rapid hemodialysis (dialysis disequilibrium syndrome) is controversial. The "reverse urea hypothesis" suggests that hemodialysis removes urea more slowly from the brain than from the plasma, creating an osmotic gradient that results in cerebral edema. The "idiogenic osmole hypothesis" proposes that an osmotic gradient between brain and plasma develops during rapid dialysis because of newly formed brain osmoles. In this review, the experimental basis for the two hypotheses are critically examined. Based on what is known about the physiology of urea and water diffusion across the blood-brain barrier, and empiric observations of brain solute composition after experimental hemodialysis, we conclude that the "reverse urea hypothesis" remains a viable explanation for dialysis disequilibrium and that rapid reduction of a high urea level in and of itself predisposes to this condition. PMID:8712203

Silver, S M; Sterns, R H; Halperin, M L

1996-07-01

207

Interdomain routing and games  

Microsoft Academic Search

We present a game-theoretic model that captures many of the intricacies of interdo- main routing in today's Internet. In this model, the strategic agents are source nodes located on a network, who aim to send tra-c to a unique destination node. The interaction between the agents is dynamic and complex { asynchronous, sequential, and based on partial information. Best-reply dynamics

Hagay Levin; Michael Schapira; Aviv Zohar

2008-01-01

208

Photonic IP routing  

Microsoft Academic Search

A photonic Internet protocol (IP) routing is proposed in which the IP address, mapped onto optical code, is recognized by performing optical correlation in the time domain in a parallel manner. Preliminary experiment shows that it can process 6.5×109 packets per second. It will help overcome the bottleneck in current electrical IP routers; i.e., the time it takes to look

K.-I. Kitayama; N. Wada

1999-01-01

209

Authenticated Adversarial Routing  

Microsoft Academic Search

The aim of this paper is to demonstrate the feasibility of authenticated\\u000athroughput-efficient routing in an unreliable and dynamically changing\\u000asynchronous network in which the majority of malicious insiders try to destroy\\u000aand alter messages or disrupt communication in any way. More specifically, in\\u000athis paper we seek to answer the following question: Given a network in which\\u000athe majority

Yair Amir; Paul Bunn; Rafail Ostrovsky

2009-01-01

210

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

211

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

2011-12-02

212

Vibrational and theoretical studies of urea and magnesium-urea complexes  

Microsoft Academic Search

.   The molecular structure and IR spectra of urea, H2NCONH2, in gas phase and in acetonitrile solution, as well as of the two complexes [MgU4Cl2] and [MgU6]Cl2 have been observed. The influence of environmental changes to geometry and spectra are shown. Various basis sets have been\\u000a employed to safeguard the validity of the reported findings, using polarization functions for all

S. G. Raptis; J. Anastassopoulou; T. Theophanides

2000-01-01

213

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

214

Desymmetrization of meso-2,5-Diallylpyrrolidinyl Ureas through Asymmetric Palladium-Catalyzed Carboamination: Stereocontrolled Synthesis of Bicyclic Ureas.  

PubMed

Lost symmetry: Fused bicyclic ureas are enantioselectively obtained through Pd-catalyzed desymmetrizing carboaminations of meso-2,5-diallylpyrrolidinyl ureas. The reactions generate a C?N and a C?C bond, and afford products with three stereocenters. One of these products was transformed to a tricyclic guanidine and then to 9-epi-batzelladine?K over several steps. PMID:23824590

Babij, Nicholas R; Wolfe, John P

2013-07-03

215

Treatment of wastewater polluted with urea by counter-current thermal hydrolysis in an industrial urea plant  

Microsoft Academic Search

In this paper, the removal of urea from industrial wastewater by thermal hydrolysis was studied via modeling and simulation of counter-current urea thermal hydrolysis reactor. The features of our proposed model are (1) the use of Nakamura equation of state to predict the vapor fugacity coefficients and UNIQUAC equation to describe the non-ideality of liquid phase, (2) the use of

M. M. Barmaki; M. R. Rahimpour; A. Jahanmiri

2009-01-01

216

Analytic Validation of an Infrared Milk Urea Assay and Effects of Sample Acquisition Factors on Milk Urea Results  

Microsoft Academic Search

The objective of this study was to determine if milk samples, as they are routinely collected by Ontario Dairy Herd Improvement, would yield accurate milk urea results with an infrared assay. This investigation involved analytic validation of the infrared assay and assessment of the effect of DHI routine sample acquisi- tion factors on milk urea results. Analytic validation of an

S. M. Godden; K. D. Lissemore; D. F. Kelton; J. H. Lumsden; K. E. Leslie; J. S. Walton

2000-01-01

217

Southern States` Routing Agency Report  

SciTech Connect

The Southern States` Routing Agency Report is a compendium of 16-southern states` routing programs and authorities for high-level radioactive materials transportation. The report includes the identification of each state`s designated routing agency and state legislation and regulations pertaining specifically to the shipment routing of high-level radioactive materials. Using information collected and compiled by the Hazardous Materials Information Group at Oak Ridge National Laboratory, the report also addresses local government routing restrictions for high-level radioactive materials transportation. Whether local or state routing restrictions have been legally challenged and found to be inconsistent and preempted by the federal Hazardous Materials Transportation Act of 1974 (49 App. USC. 1801 et seq.) is noted. Finally, the state agency and contact designated by each state`s governor to receive advance notification and shipment routing information under 10 Code of Federal Regulations (CFR) Parts 71 and 73 is listed.

Not Available

1988-02-01

218

Southern States' Routing Agency Report  

SciTech Connect

The Southern States' Routing Agency Report is a compendium of 16-southern states' routing programs and authorities for high-level radioactive materials transportation. The report includes the identification of each state's designated routing agency and state legislation and regulations pertaining specifically to the shipment routing of high-level radioactive materials. Using information collected and compiled by the Hazardous Materials Information Group at Oak Ridge National Laboratory, the report also addresses local government routing restrictions for high-level radioactive materials transportation. Whether local or state routing restrictions have been legally challenged and found to be inconsistent and preempted by the federal Hazardous Materials Transportation Act of 1974 (49 App. USC. 1801 et seq.) is noted. Finally, the state agency and contact designated by each state's governor to receive advance notification and shipment routing information under 10 Code of Federal Regulations (CFR) Parts 71 and 73 is listed.

Not Available

1988-02-01

219

Boiler using combustible fluid  

DOEpatents

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

Baumgartner, H.; Meier, J.G.

1974-07-03

220

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

Microsoft Academic Search

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

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

2012-01-01

221

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

PubMed

The aims of this study were 1) to determine whether transfer of blood urea to the gastrointestinal tract (GIT) or the efficiency of capture of urea N within the GIT is more limiting for urea N salvage, and 2) to establish the relationship between plasma urea concentration and recycling of urea N to the GIT. We used an i.v. urea infusion model in sheep to elevate the urea entry rate and plasma concentrations, thus avoiding direct manipulation of the rumen environment that otherwise occurs when feeding additional N. Four growing sheep (28.1 +/- 0.6 kg of BW) were fed a low-protein (6.8% CP, DM basis) diet and assigned to 4 rates of i.v. urea infusion (0, 3.8, 7.5, or 11.3 g of urea N/d; 10-d periods) in a balanced 4 x 4 Latin square design. Nitrogen retention (d 6 to 9), urea kinetics([(15)N2]urea infusion over 80 h), and plasma AA were determined. Urea infusion increased apparent total tract digestibility of N (29.9 to 41.3%) and DM (47.5 to 58.9%), and N retention (1.45 to 5.46 g/d). The plasma urea N entry rate increased (5.1 to 21.8 g/d) with urea infusion, as did the amount of urea N entering the GIT (4.1 to 13.2 g/d). Urea N transfer to the GIT increased with plasma urea concentration, but the increases were smaller at greater concentrations of plasma urea. Anabolic use of urea N within the GIT also increased with urea infusion (1.43 to 2.98 g/d; P = 0.003), but anabolic use as a proportion of GIT entry was low and decreased (35 to 22%; P = 0.003) with urea infusions. Consequently, much (44 to 67%) of the urea N transferred to the GIT returned to the liver for resynthesis of urea (1.8 to 9.2 g/d; P < 0.05). The present results suggest that transfer of blood urea to the GIT is 1) highly related to blood urea concentration, and 2) less limiting for N retention than is the efficiency of capture of recycled urea N by microbes within the GIT. PMID:17202392

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

2007-01-03

222

Multipath routing algorithms for congestion minimization  

Microsoft Academic Search

Abstract. Unlike traditional routing schemes that route all traffic along a single path, multipath routing strategies split the traffic among several paths in order to ease congestion. It has been widely recognized that multipath routing can be fundamentally more efficient than the traditional approach of routing along single paths. Yet, in contrast to the single-path routing approach, most studies in

Ron Banner; Ariel Orda

2007-01-01

223

Novel cardiac protective effects of urea: from shark to rat  

PubMed Central

This study was carried out to investigate novel cardioprotective effects of urea and the underlying mechanisms. The cardiac functions under oxidative stress were evaluated using Langendorff perfused isolated heart.Isolated dogfish shark hearts tolerated the oxidative stress generated by electrolysis (10?mA, 1?min) of the perfusion solution (n=4), and also showed normal cardiac functions during post-ischaemia reperfusion (n=4). The high concentration of urea (350?mM) in the heart perfusate was indispensable for maintaining the normal cardiac functions of the shark heart.Urea at 3–300?mM (n=4 for each group) protected the isolated rat heart against both electrolysis-induced heart damage and post-ischaemia reperfusion-induced cardiac injury.A concentration-dependent scavenging effect of urea (3–300?mM, n=4 for each group) against electrolysis-induced reactive oxygen species was also demonstrated in vitro.Urea derivatives as hydroxyurea, dimethylurea, and thiourea had antioxidant cardioprotective effect against the electrolysis-induced cardiac dysfunction of rat heart, but were not as effective as urea in suppressing the post-ischaemia reperfusion injury.Our results suggest that urea and its derivatives are potential antioxidant cardioprotective agents against oxidative stress-induced myocardium damage including the post-ischaemia reperfusion-induced injury.

Wang, Xintao; Wu, Lingyun; Aouffen, M'hamed; Mateescu, Mircea-Alexandru; Nadeau, Reginald; Wang, Rui

1999-01-01

224

Aqueous urea solution destabilizes Abeta(16-22) oligomers.  

PubMed

We use long multiple trajectories generated by molecular dynamics simulations to probe the stability of oligomers of Abeta(16-22) (KLVFFAE) peptides in aqueous urea solution. High concentration of urea promotes the formation of beta-strand structures in Abeta(16-22) monomers, whereas in water they adopt largely compact random coil structures. The tripeptide system, which forms stable antiparallel beta-sheet structure in water, is destabilized in urea solution. The enhancement of beta-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 beta-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. PMID:15465917

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

2004-10-01

225

Combustion of Micropowdered Biomass  

NASA Astrophysics Data System (ADS)

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

Geil, Ethan; Thorne, Robert

2009-03-01

226

A sensitive method for determining nitrogen-15 isotope in urea  

Microsoft Academic Search

A method is presented in which the 15N?at.% of urea is determined with high precision on liquid samples containing as little as 10?nmol of urea. The method involves\\u000a removal of interference from NH4\\u000a \\u000a + initially present in the sample by cation exchange. Urea in the sample is subsequently hydrolyzed to NH4\\u000a \\u000a + by the enzyme urease. Liberated NH4\\u000a \\u000a + is

S. Rysgaard; N. Risgaard-Petersen

1997-01-01

227

Chroman and tetrahydroquinoline ureas as potent TRPV1 antagonists.  

PubMed

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

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

2011-01-21

228

Fluids and Combustion Facility-Combustion Integrated Rack.  

National Technical Information Service (NTIS)

This paper describes in detail the concept of performing Combustion microgravity experiments in the Combustion Integrated Rack (CIR) of the Fluids and Combustion Facility (FCF) on the International Space Station (ISS). The extended duration microgravity e...

D. R. Francisco

1998-01-01

229

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

230

Combustion Tests with Pulverized Fuels in a Cyclone Combustion Chamber.  

National Technical Information Service (NTIS)

The objective with this project has been to establish combustion conditions and characterize material handling, milling and parameters as combustibility, ashmelting, combustion efficiency and emission index, for refined and pulverized fuels from wood, pea...

L. Eriksson

1983-01-01

231

Routes of influenza transmission.  

PubMed

Remarkably little is known definitively about the modes of influenza transmission. Thus, important health policy and infection control issues remain unresolved. These shortcomings have been exposed in national and international pandemic preparedness activities over recent years. Indeed, WHO, CDC, ECDC and the U.S. Institute of Medicine have prioritised understanding the modes of influenza transmission as a critical need for pandemic planning. Studying influenza transmission is difficult; seasonality, unpredictable attack rates, role of environmental parameters such as temperature and humidity, numbers of participants required and confounding variables all present considerable obstacles to the execution of definitive studies. A range of investigations performed to date have failed to provide definitive answers and key questions remain. Reasons for this include the fact that many studies have not sought to investigate routes of transmission as a primary objective (instead, they have evaluated specific interventions) and that fieldwork in natural settings, specifically assessing the dynamics and determinants of transmission between humans, has been limited. The available evidence suggests that all routes of transmission (droplet, aerosol and contact) have a role to play; their relative significance will depend on the set of circumstances acting at a given time. Dictating the process are factors related to the virus itself, the host and the environment. PMID:24034483

Killingley, Ben; Nguyen-Van-Tam, Jonathan

2013-09-01

232

Group Combustion of Coal Particles:.  

National Technical Information Service (NTIS)

As opposed to individual particle combustion (IPC) modeling, a group combustion (GC) theory is proposed for the combustion modeling of charcarbon particles. The group behavior for a cloud of particles represents the change in the burning characteristics d...

K. Annamalai S. C. Ramalingam W. R. Ryan

1987-01-01

233

Internal combustion engine and method  

SciTech Connect

This patent describes a method of increasing performance and eliminating detonation in an internal combustion engine. It comprises: combusting, in a combustion cylinder having a piston connected by a crank arm to a crank shaft, cooled compressed air mixed with fuel to form a combustible fuel mixture having a temperature below its autoignition temperature before combustion, the air/fuel mixture being sufficiently cool to prevent detonation of the mixture ahead of the flame front during combustion, introducing the fuel into the combustion chamber at a timed rate during the combustion whereby at least a portion of the combustion has an elapsed time of combustion at substantially constant pressure over a minimum crank angle duration of 45{degrees} after top dead center, and exhausting products of combustion from the combustion cylinder.

Haring, J.M.

1992-04-14

234

The unusual routes of administration  

Microsoft Academic Search

Summary  A wide range of administration routes can be drawn on to optimise drug absorption. Though the oral route remains the favourite\\u000a one for most drugs in many disease states, other routes are routinely used. Each has its strengths and weaknesses and needs\\u000a to be selected carefully with full consideration of the drug, its target and the release pattern required. Advances

E. Beyssac

1996-01-01

235

Urea as a cosurfactant in enhanced oil recovery processes  

SciTech Connect

A surfactant system useful for oil recovery comprising salt water, a surfactant, such as a petroleum sulfonate, and urea. Optionally, a C/sub 3/ to C/sub 8/ alcohol is additionally present as a cosurfactant.

Stapp, P. R.; Chaney, M. B.

1985-01-15

236

Urea as an Ice Nucleant for Supercooled Clouds.  

National Technical Information Service (NTIS)

Urea was observed to have extraordinary ice-nucleating properties in laboratory and natural clouds. Ice nucleation was induced in laboratory clouds at temperatures as warm as +6C. The nucleation mechanism involves the high endothermic heat of solution and...

R. G. Knollenberg

1965-01-01

237

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

238

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 1:1:1mol 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

2013-08-28

239

21 CFR 862.1770 - Urea nitrogen test system.  

Code of Federal Regulations, 2013 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)...

2013-04-01

240

Urea biosensors based on PVC membrane containing palmitic acid.  

PubMed

A new urea biosensor was prepared by immobilizing urease with four different procedures on poly(vinylchloride) (PVC) ammonium membrane electrode containing palmitic acid by using nonactine as an ammonium-ionophore. The analytical characteristics were investigated and were compared those of the biosensor prepared by using carboxylated PVC. The effect of pH, buffer concentration, temperature, urease concentration, stirring rate and enzyme immobilization procedures on the response to urea of the enzyme electrode were investigated. The linear working range and sensitivity of the biosensor were also determined. The urea biosensor prepared by using the PVC membranes containing palmitic acid showed more effective performance than those of the carboxylated PVC based biosensors. Additionally, urea assay in serum was successfully carried out by using the standard addition method. PMID:16152697

Karaku?, Emine; Pekyardimci, Sule; Esma, Kiliç

2005-01-01

241

Highly sensitive urea sensing with ion-irradiated polymer foils  

NASA Astrophysics Data System (ADS)

Recently we prepared urea-sensors by attaching urease to the inner walls of etched ion tracks within thin polymer foil. Here, alternative track-based sensor configurations are examined where the enzyme remained in solution. The conductivities of systems consisting of two parallel irradiated polymer foils and confining different urea/urease mixtures in between were examined. The correlations between conductivity and urea concentration differed strongly for foils with unetched and etched tracks, which points at different sensing mechanisms - tentatively attributed to the adsorption of enzymatic reaction products on the latent track entrances and to the enhanced conductivity of reaction product-filled etched tracks, respectively. All examined systems enable in principle, urea sensing. They point at the possibility of sensor cascade construction for more sensitive or selective sensor systems.

Fink, Dietmar; Muñoz Hernandez, Gerardo; Alfonta, Lital

2012-02-01

242

Southern States` Routing Agency Report  

SciTech Connect

The Southern States` Routing Agency Report is a compendium of 16-southern states` routing program for the transportation of high-level radioactive materials. The report identifies the state-designated routing agencies as defined under 49 Code of Federal Regulations (CFR) Part 171 and provides a reference to the source and scope of the agencies` rulemaking authority. Additionally, the state agency and contact designated by the state`s governor to receive advance notification and shipment routing information under 10 CFR Parts 71 and 73 are also listed.

Not Available

1990-03-01

243

Southern States' Routing Agency Report  

SciTech Connect

The Southern States' Routing Agency Report is a compendium of 16-southern states' routing program for the transportation of high-level radioactive materials. The report identifies the state-designated routing agencies as defined under 49 Code of Federal Regulations (CFR) Part 171 and provides a reference to the source and scope of the agencies' rulemaking authority. Additionally, the state agency and contact designated by the state's governor to receive advance notification and shipment routing information under 10 CFR Parts 71 and 73 are also listed.

Not Available

1990-03-01

244

Luminometric single step urea assay using ATP-hydrolyzing urease  

Microsoft Academic Search

An automatic enzyme kinetic luminometric method for determination of small quantities of urea in biological fluids and in microdialysates is presented. The method is based on the ATP-hydrolyzing urease reaction (urea amidohydrolase (ATP-hydrolyzing); EC 3.5.1.45), moni- tored by a luciferin-luciferase ATP reaction. The assay range is 100 pmol to 50 nmol with a detection limit of 5 mmol\\/L in the

Birgitta Naslund; Lars Stahle; Arne Lundin; Bjorn Anderstam; Peter Arner; Jonas Bergstrom

245

Mechanism of urea effect on percutaneous absorption of clonidine  

Microsoft Academic Search

The urea effect on skin permeation of clonidine was investigated to reduce a log time and to increase a permeability. ICR\\u000a mouse skin and human skin were used and were assumed to be a two-layer membrane consisted of stratum corneum and viable epidermis.\\u000a The urea acted as a skin denaturant and humectant in the whole epidermis. Also it enhanced the

Young Rho Byun; Seo Young Jeong; Young Ha Kim

1989-01-01

246

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

247

Reliability of haemodialysis urea kinetic modelling in children  

Microsoft Academic Search

The reliability of urea kinetic modelling (UKM) in paediatric haemodialysis was tested by comparing results of the classic variable volume model (UKM3), a recently introduced two-sample modification of this (UKM2) and direct quantification by a partial dialysate collection method (PDC). Urea generation rate (G) was also found from a 1-week collection of dialysate and urine (OWC). Nine children aged 2–18

Tom Buurl; Mark G. Bradbury; Stephen W. Smye; J. Trevor Brocklebank

1994-01-01

248

Measurement of urea and ammonium concentrations in gastric juice  

Microsoft Academic Search

AIM--To study the effect of known interference in the measurement of urea and ammonium concentrations in samples of gastric juice. METHODS--The effect of pH and ammonium concentration on the o-pthalaldehyde method, the diacetylmonoxime method, a Berthelot linked method and an enzymatic urease method for the measurement of urea in gastric juice was therefore conducted. An enzymatic method of the measurement

W D Neithercut; A M el Nujumi; K E McColl

1993-01-01

249

Agronomic performance of urea briquette applicator in transplanted rice  

Microsoft Academic Search

Field trials were conducted in the Philippines and India during 1989 and 1990 seasons to study comparative yield responses of transplanted rice (Oryza sativa L.) to pillow-shaped urea briquettes (UB) deep placed by an applicator (prototype developed by IFDC) and by hand immediately after transplanting. The applicator-placed UB consistently increased grain yields over the split-applied prilled urea, and the additional

N. K. Savant; P. S. Ongkingco; F. D. Garcia; S. S. Dhane; R. R. Khadse; S. A. Chavan; K. S. Rao

1992-01-01

250

Fractionation of urea-pretreated squid visceral oil ethyl esters  

Microsoft Academic Search

Ethyl esters of squid (Illex argentinus) visceral oil contained 11.8% eicosapentaenoic acid (EPA) and 14.9% docosahexaenoic acid (DHA). The esters were treated with\\u000a urea to increase the contents of EPA and DHA. The non-urea complexing ethyl esters of squid visceral oil contained 28.2% EPA\\u000a and 35.6% DHA. This mixture was fractionated by molecular distillation to further increase the EPA or

Lucy Sun Hwang

2001-01-01

251

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

252

Curing process of phenol-urea-formaldehyde-tannin (PUFT) adhesives  

Microsoft Academic Search

Summary  Phenol-urea-formaldehyde-tannin (PUFT) adhesives have been prepared by copolymerization at room temperature of pine bark tannins\\u000a with phenol-urea-formaldehyde (PUF) prepolymers prepared under varying operating conditions. Differential scanning calorimetry\\u000a (DSC) and dynamic mechanical analysis (DMA) have been used to analyse the curing of prepolymers and adhesives. DSC curves\\u000a were obtained at three different heating rates and, by means of the Model Free

G. Vázquez; F. López-Suevos; J. González-Alvarez; G. Antorrena

2005-01-01

253

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

254

Use of sucrose fatty acid esters in foliar application of urea  

Microsoft Academic Search

Although urea is a good source of nitrogen for foliar application of nitrogen, only a small amount of the urea supplied can be absorbed by the leaves. To increase the absorption of urea by the leaves, the surface must first be wetted to enable urea to penetrate the leaf cuticle or stomata (Frank 1967). The ability of a liquid to

Won Kae Choi; Motoki Ikeda; Yoshio Yamada

1989-01-01

255

Proteins and Amino Acids Triiodothyronine Administration Affects urea Synthesis in Rats  

Microsoft Academic Search

The purpose of the present study was to elucidate the mechanism by which thyroid hormone alters urea synthesis. The relative importance of urea cycle enzyme activities, substrate levels or the levels of urea cycle intermediates on urea production was investi gated in a set of four experiments in which rats were fed a diet supplemented with 6-propyl-2-thiouracil (PTU, a thyroid

KAZOTOSHI HAYASE; GORO YONEKAWA; AKIRA YOSHIDA

256

Highway Route Designation Criteria for Bicycle Routes: Handbook.  

National Technical Information Service (NTIS)

The Handbook is designed to simplify the task of selecting and designating streets and highways for bike routes. The topics covered include the definition of bike routes, the purpose(s) which affect suitability, approaches to planning and selecting bike r...

W. C. Wilkinson C. G. Moran

1986-01-01

257

Analytical Analysis of Vehicle Routing and Inventory Routing Problems.  

National Technical Information Service (NTIS)

The objective of the project is to perform analytical analyses of heuristics for the Vehicle Routing Problem (VRP) and apply the results in models that integrate vehicle routing with other issues important to the firm. Our major accomplishments are: (1) D...

1998-01-01

258

Combustion Integrated Rack  

NASA Video Gallery

This is one of a series of short features about some of the experiment racks on station. This video focuses on the Combustion Integrated Rack (CIR) and features the Multi-User Droplet Combustion Apparatus (MDCA) and the Flame Extinguishment Experiment (FLEX).

Mark Garcia

2013-05-13

259

Combustion chamber construction  

Microsoft Academic Search

A combustion chamber is described for use in gas turbine engines, the chamber comprising: an inlet for receiving air and fuel to be burned; an outlet for expelling products of combustion; high strength structural frame means disposed between the inlet and the outlet for supporting mechanical forces associated with the chamber; liner means cooperating with the frame and defining a

A. P. Sterman; T. G. Wakeman; J. J. Williams

1986-01-01

260

Catalytically enhanced combustion process  

SciTech Connect

This patent describes a fuel having improved combustion efficiency. It comprises a petroleum based liquid hydrocarbon; and a combustion catalyst comprising from about 18 to about 21 weight percent naphthalene, from about 75 to about 80 weight percent toluene, and from about 2.8 to about 3.2 weight percent benzyl alcohol.

Rodriguez, C.

1992-05-26

261

Opportunities in Pulse Combustion.  

National Technical Information Service (NTIS)

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...

D. L. Brenchley H. J. Bomelburg

1985-01-01

262

Sources of Combustion Irreversibility  

Microsoft Academic Search

Approximately 1\\/3 of the useful energy of the fuel is destroyed during the combustion process used in electrical power generation. This study is an attempt to clarify and categorize the reasons for the exergy destruction taking place in combustion processes. The entropy production is separated into three subprocesses: (1) combined diffusion\\/fuel oxidation, (2) “internal thermal energy exchange” (heat transfer), and

W. R. DUNBAR; N. LIOR

1994-01-01

263

Internal combustion engine  

Microsoft Academic Search

An improvement to an internal combustion engine is disclosed that has a fuel system for feeding a fuel-air mixture to the combustion chambers and an electrical generation system, such as an alternator. An electrolytic cell is attached adjacent to the engine to generate hydrogen and oxygen upon the application of a voltage between the cathode and anode of the electrolytic

Valdespino

1981-01-01

264

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

265

NiO nanoparticle-based urea biosensor.  

PubMed

NiO nanoparticles (NiO-NPs) have been exploited successfully for the fabrication of a urea biosensor. A thin film of NiO nanoparticles deposited on an indium tin oxide (ITO) coated glass substrate serves as an efficient matrix for the immobilisation of urease (Ur), the specific enzyme for urea detection. The prepared bioelectrode (Ur/NiO-NP/ITO/glass) is utilised for urea sensing using cyclic voltammetry and UV-visible spectroscopy. NiO nanoparticles act as electro-catalytic species that are based on the shuttling of electrons between Ni(2+) and Ni(3+) in the octahedral site and result in an enhanced electrochemical current response. The prepared bioelectrode (Ur/NiO-NPs/ITO/glass) exhibits a high sensitivity of 21.3 ?A/(mM (*) cm(2)) and a good linearity in a wide range (0.83-16.65 Mm) of urea concentrations with fast response time of 5s. The low value of the Michaelis-Menten constant (K(m)=0.34 mM) indicates the high affinity of Ur towards the analyte (urea). The high catalytic activity, along with the redox behaviour of NiO-NPs, makes it an efficient matrix for the realisation of a urea biosensor. PMID:22947517

Tyagi, Manisha; Tomar, Monika; Gupta, Vinay

2012-08-17

266

Urea-Water Solvation Forces on Prion Structures  

PubMed Central

Solvation forces are crucial determinants in the equilibrium between the folded and unfolded state of proteins. Particularly interesting are the solvent forces of denaturing solvent mixtures on folded and misfolded states of proteins involved in neurodegeneration. The C-terminal globular domain of the ovine prion protein (1UW3) and its analogue H2H3 in the ?-rich and ?-rich conformation were used as model structures to study the solvation forces in 4 M aqueous urea using molecular dynamics. The model structures display very different secondary structures and solvent exposures. Most protein atoms favor interactions with urea over interactions with water. The force difference between protein–urea and protein–water interactions correlates with hydrophobicity; i.e., urea interacts preferentially with hydrophobic atoms, in agreement with results from solvent transfer experiments. Solvent Shannon entropy maps illustrate the mobility gradient of the urea–water mixture from the first solvation shell to the bulk. Single urea molecules replace water in the first solvation shell preferably at locations of relatively high solvent entropy.

2012-01-01

267

Combustion Synthesis of Magnesium Aluminate  

SciTech Connect

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

Kale, M. A. [Physics Department, S.V.S.S. College of Engineering and Research, Nagpur 4411 10 (India); Joshi, C. P. [Physics Department, Ramdeobaba Engineering College, Katol Road, Nagpur 440 013 (India); Moharil, S. V. [Physics Department, RTM Nagpur University, Nagpur, 440033 (India)

2011-10-20

268

Stratified-combustion type internal combustion engine with pre-combustion-chamber  

Microsoft Academic Search

A stratified-combustion type internal combustion engine has a rich fuel-air mixture passage and an air passage both open into the main combustion chamber. A pre-combustion chamber is located adjacent to the main combustion chamber and has a connecting port to the main combustion chamber adjacent to the opening of the rich fuel-air mixture passage. The rich fuel-air mixture is supplied

Goto

1976-01-01

269

Catalyzed Decomposition of Urea. Molecular Dynamics Simulations of the Binding of Urea to Urease  

PubMed Central

We present the results of molecular dynamics simulations on the urea/urease system. The starting structure was prepared from the 2.0Å crystal structure of Benini et al. of DAP-inhibited urease (PDB code 3UBP),1 and the trimeric structure (2479 residues) resulted in 180K atoms after solvation by water. The force field parameters were derived using the bonded model approach described by Hoops et al.2 Three different systems were analyzed, each one modeling a different protonation pattern for the His320 and His219 residues. In each case, the three monomers of urease have been analyzed separately. The time averaged structures observed in the three monomers suggest that urease could follow two different competitive mechanisms. A “protein assisted proton transfer” mechanism points to Asp221 as crucial for catalysis. An “Asp mediated proton transfer” involves the transfer of a proton from the bridging OH to a NH2 moiety of urea, assisted by Asp360 in the active site. The impact of the simulation results on our understanding of urease catalysis are discussed in detail.

Estiu, Guillermina; Merz, Kenneth M.

2008-01-01

270

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

271

The influence of combustion synthesis conditions on the ?-Al 2 O 3 powder preparation  

Microsoft Academic Search

Fuel type and fuel\\/aluminium nitrate molar ratio proved to be of great importance during the preparation of ?-Al2O3 powders. A stoichiometric amount of urea (U) enabled the formation of ?-Al2O3 with a surface area of 24 m2\\/g directly from the combustion reaction. Monoethanolamine, triethylenetetramine, trishydroxymethylaminomethane, and triethanolamine\\u000a yield amorphous powders. This behaviour was explained by the reaction mechanism, which requires the

Robert Ianos; Ioan Lazau; Cornelia Pacurariu

2009-01-01

272

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

273

Anion Binding in MetalOrganic Frameworks Functionalized with Urea Hydrogen-Bonding Groups  

Microsoft Academic Search

A series of metal-organic frameworks (MOFs) functionalized with urea hydrogen-bonding groups has been synthesized and structurally analyzed by single-crystal X-ray diffraction to evaluate the efficacy of anion coordination by urea within the structural constraints of the MOFs. We found that urea-based functionalities may be used for anion binding within metal-organic frameworks when the tendency for urea{hor_ellipsis}urea self-association is decreased by

Radu Custelcean; Bruce A Moyer; Vyacheslav S. Bryantsev; Benjamin P. Hay

2006-01-01

274

Effects of Postdialysis Urea Rebound on the Quantification of Pediatric Hemodialysis  

Microsoft Academic Search

Urea rebound (UR) causes single pool urea kinetic modeling (UKM), which is based on end-dialysis urea instead of its equilibrated value (Ceq), to erroneously quantify hemodialysis (HD) treatment. We estimated the impact of postdialysis UR on the results of formal variable volume single pool (VVSP) UKM [Kt\\/V, urea distribution volume (V), urea generation rate (G), normalized protein catabolic rate (nPCR),

2000-01-01

275

How bad is selfish routing?  

Microsoft Academic Search

We consider the problem of routing traffic to optimize the performance of a congested network. We are given a network, a rate of traffic between each pair of nodes, and a latency function for each edge specifying the time needed to traverse the edge given its congestion; the objective is to route traffic such that the sum of all travel

Tim Roughgarden; Éva Tardos

2002-01-01

276

How Bad is Selfish Routing?  

Microsoft Academic Search

We consider the problem of routing traffic to optimize the performance of a con- gested network. We are given a network, a rate of traffic between each pair of nodes, and a latency function for each edge specifying the time needed to traverse the edge given its congestion; the objective is to route traffic such that the sum of all

Tim Roughgarden; Eva Tardost

2000-01-01

277

Path Diversity Aware Interdomain Routing  

Microsoft Academic Search

Abstract—As the Internet becomes the critical information infrastructure for both personal and business applications, fast and reliable routing protocols need to be designed to maintain the performance of those applications in the presence of failures. Today’s interdomain routing protocol, BGP, is known to be slow in reacting and recovering from network failures. Increasing path diversity by advertising multiple paths is

Feng Wang; Lixin Gao

2009-01-01

278

Dynamic Message Routing Using Processes  

NASA Astrophysics Data System (ADS)

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

Scheibler, Thorsten; Karastoyanova, Dimka; Leymann, Frank

279

Sybil-Resistant DHT Routing  

Microsoft Academic Search

Distributed Hash Tables (DHTs) are very ecien t distributed systems for routing, but at the same time vulnerable to disruptive nodes. Designers of such systems want them used in open networks, where an adversary can perform a sybil attack by introducing a large number of corrupt nodes in the network, considerably degrading its performance. We introduce a routing strategy that

George Danezis; Chris Lesniewski-laas; M. Frans Kaashoek; Ross J. Anderson

2005-01-01

280

Scalable routing on flat names  

Microsoft Academic Search

We introduce a protocol which routes on flat, location-independent identifiers with guaranteed scalability and low stretch. Our design builds on theoretical advances in the area of compact routing, and is the first to realize these guarantees in a dynamic distributed setting.

Ankit Singla; P. Brighten Godfrey; Kevin R. Fall; Gianluca Iannaccone; Sylvia Ratnasamy

2010-01-01

281

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

282

Securing the Nimrod Routing Architecture  

Microsoft Academic Search

This paper describes the work undertaken to secure Nimrod, a complex and sophisticated routing system that unifies interior and exterior routing functions. The focus of this work is countering attacks that would degrade or deny service to network subscribers. The work began with an analysis of security requirements for Nimrod, based on a hybrid approach that refines top-down requirements generation

Karen E. Sirois; Stephen T. Kent

1997-01-01

283

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

284

Effect of silver addition on the properties of combustion synthesized nanocrystalline LiCoO 2  

Microsoft Academic Search

Nanocrystalline (?50nm) LiCoO2 powders containing 0–10mol% of Ag have been prepared by combustion synthesis using citrate–nitrate combustion route. Thermal analyses show a sharp decomposition of the gel at ?177°C for pristine LiCoO2. With addition of silver, the decomposition becomes sluggish and it completes only above 430°C. X-ray powder diffraction analyses show an increase in lattice parameter, c, with increasing Ag

Paromita Ghosh; S. Mahanty; R. N. Basu

2008-01-01

285

Life cycle modelling and comparative assessment of the environmental impacts of oxy-fuel and post-combustion CO 2 capture, transport and injection processes  

Microsoft Academic Search

The oxy-fuel combustion CO2 capture route and post-combustion CO2 capture route involve different energy consumption rates and subsequent environmental impacts. The holistic perspective offered by Life Cycle Assessment (LCA) can help decision makers to compare alternative CO2 capture and storage technologies in a life cycle perspective. This paper, at first, introduces the principles of the dynamic LCA model developed for

Zhenggang Nie; Anna Korre; Sevket Durucan

2011-01-01

286

Thermal stability of complex oxide combustion catalyst supports  

Microsoft Academic Search

As part of a search for more thermostable supports for combustion catalysts for gas turbine applications, a series of complex oxide materials were prepared by sol-gel synthesis and two different coprecipitation routes. The materials were chosen on the basis of literature studies; two hexaaluminates (LaAlââOââ and BaMnAlââO{sub 19-a}), a perovskite (SrZrOâ), a spinel (MgAlâOâ), and a pyrochlore (LaâZrâOâ). After synthesis,

Marcus F. M. Zwinkels; Stéphanie Druesne; P. Govind Menon; E. Bjoernbom; S. G. Jaeraas

1998-01-01

287

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

288

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

289

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

2013-01-02

290

Optimum Routeing: Analytical Constraint of Search Space.  

National Technical Information Service (NTIS)

Algorithms are being developed for route optimization using the geometric constraints imposed on route geometry by zero-gradient conditions on route costs. Two related techniques are under consideration. The first takes a spatial search approach using the...

W. G. Semple

1995-01-01

291

46 CFR 45.175 - Applicable routes.  

Code of Federal Regulations, 2011 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,...

2011-10-01

292

46 CFR 45.175 - Applicable routes.  

Code of Federal Regulations, 2012 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,...

2012-10-01

293

N[sub 2]O formation in combustion systems  

SciTech Connect

The objective of this project is to characterize N[sub 2]O emissions from combustion sources emphasizing N[sub 2]O emissions from post-combustion selective gas phase NO[sub x] reduction processes and reburning. The processes to be evaluated include ammonia, urea and cyanuric acid injection and reburning. The project includes pilot-scale testing at two facilities supported by chemical kinetic modeling. Testing will be performed on both a gas-fired plug flow combustor and a pulverized-coal fired combustor. Work performed to date has included the performance of the initial detailed chemical kinetics calculations. These calculations showed that both urea and cyanuric acid produce significant quantities of N[sub 2]O, while NH[sub 3] injection produced negligible amounts. These kinetics data support limited test results reported for cyanuric acid and ammonia injection. Laboratory work to evaluate the selective gas phase NO[sub x] reduction processes listed above will begin in the gas-fired facility early in CY 1990. Testing to evaluate reburning at the coal-fired facility is currently planned to be performed in parallel with the testing at the gas-fired facility. Following completion of that work, additional kinetics calculations will be performed.

Not Available

1989-11-01

294

N[sub 2]O formation in combustion systems  

SciTech Connect

The objective of this project is to characterize N[sub 2]O emissions from combustion sources emphasizing N[sub 2]O emissions from post-combustion selective gas phase NO[sub x] reduction processes and reburning. The processes to be evaluated include selective noncatalytic NO[sub x] control (ammonia, urea and cyanuric acid injection), and reburning. The project includes pilot-scale testing at two facilities supported by chemical kinetic modeling. Testing is being performed on both a gas-fired plug flow combustor and a pulverized-coal fired combustor. Work performed to date has included the performance of the initial detailed chemical kinetics calculations. These calculations showed that both urea and cyanuric acid produce significant quantities of N[sub 2]O, while NH[sub 3] injection produced negligible amounts, These kinetics data support limited test results reported for cyanuric acid and ammonia injection. Laboratory work to evaluate the selective gas phase NO[sub x] reduction processes listed above has begun. Testing to evaluate reburning at the coal-fired facility is being performed in parallel with the testing at the gas-fired facility. Following completion of the test work, additional kinetics calculations will be performed.

Not Available

1990-03-01

295

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

2008-04-24

296

THE TEMPERATURE COEFFICIENT OF THE UREA DENATURATION OF EGG ALBUMIN  

PubMed Central

Evidence is brought forward to show that at concentrations of urea high enough to split the egg albumin molecule the solubility changes produced by urea are profoundly modified. The degree of precipitation after dialysis is the net result of two changes produced by the urea: the first, normally spoken of as denaturation, which makes the protein insoluble in dilute solution and the second, a splitting of the molecule which makes it soluble. These two reactions may proceed independently and simultaneously or the second reaction may follow the first, taking place in the denatured molecule only. In view of the decrease in the opalescence with time, the latter process is more probable. Both of these reactions have positive temperature coefficients, but as the concentration of urea increases the second reaction is more affected by increase in temperature than the first, and consequently the resulting opalescence decreases rather than increases with temperature. This accounts for and explains reports of negative temperature coefficients of denaturation, when denaturation is measured by the amount of insoluble material found on dilution. The occurrence of these two reactions, one leading to an increase and the other to a decrease in the amount of insoluble protein, should be taken into account when denaturation changes in egg albumin with urea are studied.

Clark, Janet Howell

1945-01-01

297

Measurement of urea and ammonium concentrations in gastric juice.  

PubMed Central

AIM--To study the effect of known interference in the measurement of urea and ammonium concentrations in samples of gastric juice. METHODS--The effect of pH and ammonium concentration on the o-pthalaldehyde method, the diacetylmonoxime method, a Berthelot linked method and an enzymatic urease method for the measurement of urea in gastric juice was therefore conducted. An enzymatic method of the measurement of ammonium in gastric juice was also assessed. RESULTS--The o-pthalaldehyde and the enzymatic urease methods were unaffected by a low gastric juice pH, ammonium concentrations of 10 mmol/l, and had interassay coefficients of variation of 3.9-5.6% and 2.8-10.6%, respectively, over a urea concentration of 2.5 mmol/l-20 mmol/l. The Berthelot linked method resulted in low gastric juice urea concentrations. The enzymatic method of ammonium measurement also proved suitable when the effect of low gastric juice pH was controlled. CONCLUSION--Interference by low pH did not explain the differences in reports of gastric juice urea or ammonium concentrations.

Neithercut, W D; el Nujumi, A M; McColl, K E

1993-01-01

298

Understanding Pulverised Coal Combustion,  

National Technical Information Service (NTIS)

Reviews recent literature, mainly post 1980, on the fundamental processes and mechanisms of pulverized coal combustion. Three main sections cover devolatilization, char oxidation and pollutant formation. The section on devolatilization covers the physical...

G. F. Morrison

1986-01-01

299

Combustion Species Sampling.  

National Technical Information Service (NTIS)

A combustion chamber for propellant studies was developed and molecular beam gas sampling systems were analyzed in this program. A unique laboratory combustor design provides sampling from any part of the chamber by axial movement of a gas extraction port...

J. Kahrs

1968-01-01

300

Combustible Cartridge Case Characterization.  

National Technical Information Service (NTIS)

The beater additive process for manufacturing combustible cartridge cases is superior to the solvent resin, post-impregnation process. However, the current beater additive resins do not produce as good a product as the solvent-resin system. The objective ...

R. I. Brabets

1984-01-01

301

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

302

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

303

Combustion synthesis of YAG:Ce and related phosphors  

NASA Astrophysics Data System (ADS)

YAG:Ce is an important phosphor having applications in various fields ranging from solid state lighting to scintillation detectors. YAG phosphors doped with activators are mainly synthesized by solid state reaction techniques that require high sintering temperatures (above 1500°C) to eliminate YAM and YAP phases. Though several soft chemical routes have been explored for synthesis of YAG, most of these methods are complex and phase pure materials are not obtained in one step, but prolonged annealing at temperatures around 1000°C or above become necessary. One step combustion synthesis of YAG:Ce3+ and related phosphors carried out at 500°C furnace temperature is reported here. Activation with Ce3+ could be achieved during the synthesis without taking recourse to any post-combustion thermal treatment. LEDs prepared from the combustion synthesized YAG:Ce3+, exhibited properties comparable to those produced from the commercial phosphor.

Gupta, K. V. K.; Muley, A.; Yadav, P.; Joshi, C. P.; Moharil, S. V.

2011-11-01

304

Online multicommodity routing with timewindows  

Microsoft Academic Search

Abstract. We consider a multicommodity routing problem, where de- mands,are released,online and,have,to be routed,in a network,during specified time windows.,The objective,is to minimize,a time,and,load dependent,convex,cost function,of the aggregate,arc flow. First, we study the fractional routing variant. We present two online algorithms, called Seq and Seq,. We prove that for polynomial price functions with nonnegative coecients,and maximum

TOBIAS HARKS; STEFAN HEINZ; MARC E. PFETSCH; TJARK VREDEVELD

2007-01-01

305

Crystal structure of a bacterial homologue of the kidney urea transporter  

SciTech Connect

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

Levin, Elena J.; Quick, Matthias; Zhou, Ming; (Columbia)

2010-03-19

306

Planned Route Optimization For Real-Time Vehicle Routing  

Microsoft Academic Search

This paper reviews and classifies the work done in the field of dynamic vehicle routing. We focus, in particular, on problems\\u000a where the uncertainty comes from the occurrence of new requests. Problem-solving approaches are investigated in contexts where\\u000a consolidation of multiple requests onto the same vehicle is allowed and addressed through the design of planned routes. Starting\\u000a with pure myopic

Soumia Ichoua; Michel Gendreau; Jean-Yves Potvin

307

Combustion of fuel blends  

Microsoft Academic Search

An experimental investigation of the combustion of various kerosene-diesel and alcohol-diesel fuel blends is presented. Tests are conducted in a continuous flow combustor to study the effect of fuel blends on the combustion process and pollutants in the exhaust gases. Exhaust analyses of CO, CO2, O2, NOx, HC and soot mass concentration are presented. For the ethanol alcohol-diesel blends, a

K. R. Asfar; H. Hamed

1998-01-01

308

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

309

Effect of oxygenated liquid additives on the urea based SNCR process.  

PubMed

An experimental investigation was performed to study the effect of oxygenated liquid additives, H(2)O(2), C(2)H(5)OH, C(2)H(4)(OH)(2) and C(3)H(5)(OH)(3) on NO(x) 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 with 6% excess oxygen in flue gases. The desired levels of initial NO(x) (500ppm) were achieved by doping the fuel gas with ammonia. Experiments were performed throughout the temperature range of interest, i.e. from 800 to 1200 degrees C for the investigation of the effects of the process additives on the performance of aqueous urea DeNO(x). With H(2)O(2) addition a downward shift of 150 degrees C in the peak reduction temperature from 1130 to 980 degrees C was observed during the experimentation, however, the peak reduction efficiency was reduced from 81 to 63% when no additive was used. The gradual addition of C(2)H(5)OH up to a molar ratio of 2.0 further impairs the peak NO(x) reduction efficiency by reducing it to 50% but this is accompanied by a downward shift of 180 degrees C in the peak reduction temperature. Further exploration using C(2)H(4)(OH)(2) suggested that a 50% reduction could be attained for all the temperatures higher than 940 degrees C. The use of C(3)H(5)(OH)(3) as a secondary additive has a significant effect on the peak reduction efficiency that decreased to 40% the reductions were achievable at a much lower temperature of 800 degrees C showing a downward shift of 330 degrees C. PMID:19540035

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

2009-06-21

310

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

311

Combustion synthesis and luminescent properties of a new material Li 2(Ba 0.99,Eu 0.01)SiO 4:B 3+ for ultraviolet light emitting diodes  

Microsoft Academic Search

Using urea as fuel and boric as flux, a novel bluish green emitting phosphor Li2(Ba0.99,Eu0.01)SiO4:B3+ has been successfully synthesized using a combustion method. The material has potential application as the fluorescent material for ultraviolet light-emitting diodes (UV-LEDs). The dependence of the properties of Li2(Ba0.99,Eu0.01)SiO4:B3+ phosphors upon urea concentration, boric acid doping and initiating combustion temperature were investigated. The crystallization and

Shanshan Yao; Donghua Chen

2008-01-01

312

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

PubMed

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

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

2011-01-21

313

A modified algorithm of the single pool urea kinetic model.  

PubMed

Urea Kt/V, calculated according to the variable volume single pool urea kinetic model (UKM), has been accepted as the yardstick reflecting the adequacy of haemodialysis therapy. However, the classical algorithm of UKM requires great care in dialyser urea clearance (K) measurement in order to avoid major inaccuracies in estimating the urea distribution volume (V). Thus, we suggest a modified algorithm of UKM which avoids the measurement of K. It assumes an arbitrary V value and then calculates kinetically K as a function of the assumed V value. The rationale of the modified algorithm can be derived from the knowledge that the classical algorithm imposes a proportionality ration between K and V: given a particular set of data, a change in the attributed value of K leads to a proportional change in the calculated V value, so that the ratio K/V remains nearly constant. Aims of the study were (1) to validate the modified algorithm by comparing the resulting Kt/V and normalised protein catabolic rate (NPCR) values with the homologous ones obtained using the classical algorithm in a group of 33 patients on thrice-weekly haemodialysis; plasma water urea concentrations were used with the classical algorithm (CApw) and the modified algorithm (MApw); and (2) to verify the possibility of using plasma urea concentrations with the modified algorithm (MAp) instead of the more rigorous plasma water concentrations. NPCR (g/kg per day) was 1.33 +/- 0.05 in CApw, 1.29 +/- 0.05 in MApw and 1.28 +/- 0.04 in MAp. Kt/V was 1.27 +/- 0.03 in CApw, 1.25 +/- 0.03 in MApw and 1.26 +/- 0.03 in MAp.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2113650

Casino, F G; Basile, C; Gaudiano, V; Lopez, T

1990-01-01

314

[Renal regulation of the excretion of urea in fasting camels].  

PubMed

Experiments were performed with young two-humped camels exposed to 36-hour starvation with free access to water. The renal functions were measured by the standard clearance method. In spite of the administration of 20 micrograms DDAVP, a higher urine flow rate was recorded in the camels subjected to control measurements (feed intake) than in the fasting period (1.45 +/- 0.06 vs. 0.96 +/- 0.06 ml . min-1, P less than less than 0.001). On the second day of fasting the camels had a significantly reduced glomerular filtration rate (GFR 317.5 +/- 23.2 vs. 170.2 +/- 17.4 ml . min-1, P less than 0.001), urea output (700.5 +/- 62.9 vs. 352.2 +/- 64.7 mumol . min-1, P less than 0.005), and fractional excretion of urea (26.9 +/- 2.8 vs. 17.9 +/- 1.7%, P less than 0.01), whereas their tubular resorption. of urea (Reab urea/GFR) increased (6.28 +/- 0.61 vs. 9.12 +/- 0.82 mumol . ml-1, P less than 0.02). No significant difference was found in the concentration of urea in plasma in the fed camels and in fasting camels (8.55 +/- 0.64 vs. 11.18 +/- 1.09 mmol . l-1, N. S.). The creatinine inulin clearance ratio (C creat/Cin) was 0.92 +/- 0.07 when the animals were fed and 1.17 +/- 0.05 when the animals starved (P less than 0.001); this suggests that the clearance of endogenous creatinine is not suitable for GFR measurement in camels under different conditions of nutrition. The kidneys of camels regulate the excretion of urea during short-time fasting mainly through the reduction of glomerular filtration rate and just partly through an increased tubular resorption. PMID:6438869

Leng, L; Bod'a, K; Tasenov, K T; Karinbaev, R S; Makasev, E K; Rachimberdiev, S A; Tlegenov, D K; Jurgalieva, L A

1984-09-01

315

Rethinking iBGP routing  

Microsoft Academic Search

The Internet is organized as a collection of administrative domains, knownasAutonomousSystems(ASes). TheseASesinteractthrough theBorderGatewayProtocol(BGP)thatallowsthemtosharereach- ability information. Adjacent routers in distinct ASes use external BGP (eBGP), whereas in a given AS routes are propagated over internal BGP (iBGP) sessions between any pair of routers. In large ASes where a logical full-mesh is not possible, confederations or route reflectors (RRs) are used. However,

Iuniana M. Oprescu; Mickael J. F. Meulle; Steve Uhlig; Cristel Pelsser; Olaf Maennel; Philippe Owezarski

2010-01-01

316

Cooperative Routing in Wireless Networks  

Microsoft Academic Search

The joint problem of transmission-side diversity and routing in wireless networks is studied. It is assumed that each node in the network is equipped with a single omni-directional antenna and multiple nodes are allowed to coordinate their transmissions to achieve transmission-side diversity. The problem of finding the minimum energy route under this setting is formulated. Analytical asymptotic results are obtained

Amir Ehsan Khandani; Eytan Modiano; Jinane Abounadi; Lizhong Zheng

317

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

318

Hierarchical buffered routing tree generation  

Microsoft Academic Search

This paper presents a solution to the problem of per- formance-driven buffered routing tree generation for VLSI cir- cuits. Using a novel bottom-up construction algorithm and a local neighborhood search strategy, our polynomial time algorithm finds the optimum solution in an exponential-size solution sub- space. The final output is a buffered rectilinear Steiner routing tree that connects the driver of

Amir H. Salek; Jinan Lou; Massoud Pedram

2002-01-01

319

On Conguring BGP Route Reectors  

Microsoft Academic Search

The Border Gateway Protocol (BGP) is the standard protocol for exchanging routing information between border routers of Autonomous Systems (ASes) in today's Internet. Within an AS, border routers exchange externally-learned BGP route advertisements via Internal- BGP (I-BGP) peerings. Naive solutions for these I-BGP peering sessions (e.g., based on full-mesh topologies) simply cannot scale to the sizes of modern AS networks.

Yuri Breitbart; Minos Garofalakis; Anupam Gupta; Amit Kumar; Rajeev Rastogi

320

Reverse flood routing with the inverted Muskingum storage routing scheme  

NASA Astrophysics Data System (ADS)

Motivation On occasion, flood related questions are posed in the reverse from the conventional sense, e.g.: Which inflow created the flow observed at cross-section X, or the flood profile observed along reach Y? This is a signal identification type problem (hydrologic forensics). A related question concerns the operation of a reservoir, via optimal outflow control, so as to minimise downstream flood damage. Solution of the aforementioned problems requires routing of floods in the upstream direction. This is an inverse problem, and as such it is not well posed. In routing against the wave propagation, small errors in the flow measurements, or rounding errors, are amplified leading to instability, i.e., to spurious, large changes in the response (inflow hydrograph). Therefore, for the reverse solution to be stable it must be constrained by a smoothness condition; this however does not ensure its uniqueness. Storage routing models as approximate diffusion wave models By appropriate choice of their parameter values, storage routing models approximate closely diffusion-wave (DW) behaviour, if dominant flood propagation mode is that of kinematic waves (KW), which is very often true. We solve the flood signal identification problem by reversing the Muskingum routing scheme. The Muskingum routing scheme derives from a first-order accurate FD discretisation of the KW equation yet yields second-order accurate DW solutions by matching the numerical diffusion coefficient of that KW equation solution scheme to the DW equation’s hydraulic diffusion coefficient. Formulation and testing of a reverse routing scheme based on Muskingum routing Theoretical analysis of the reversed Muskingum routing scheme yields nominal grid design rules; however, we study optimal grid design mainly by numerical experimentation. First, we reverse an exact outflow hydrograph (a single-wave solution of the convection-diffusion equation), and then demonstrate the scheme’s ability to reverse-resolve composite hydrographs, also generated analytically. In a range of grid parameters, the reverse routing scheme backtracks the wave propagation in both instances very well, regaining accurately the inflow signals. Seeding the generated field data with random error causes instability in the calculation. To cope with spurious oscillations, the reversed solutions are conditioned via smoothing, applying two methods of smoothing: (i) simple low-pass filtering and (ii) optimisation (second derivative control vs. minimum shape errors). The recovered inflow hydrographs are again of good quality. Finally, we compare our method to that of Bruen & Dooge (2007), who back-routed flow hydrographs in a prismatic channel using a scheme for the reverse solution of the St. Venant equations of flood wave motion. The reversed Muskingum routing scheme is shown to at least match the accuracy of the box-scheme for reverse routing with the St. Venant equations. This study leads us to conclude that the good fidelity of the inflow recovery rests on the simplicity of the Muskingum storage reverse routing scheme, which endows it with numerical robustness and computational efficiency.

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

2010-09-01

321

Tyrosine urea muscarinic acetylcholine receptor antagonists: achiral quaternary ammonium groups.  

PubMed

Tyrosine ureas had been identified as potent muscarinic receptor antagonists with promising in vivo activity. Controlling the stereochemistry of the chiral quaternary ammonium center had proved to be a serious issue for this series, however. Herein we describe the preparation and SAR of tyrosine urea antagonists containing achiral quaternary ammonium centers. The most successful such moiety was the 2-methylimidazo[2,1-b][1,3]thiazol-7-ium group which yielded highly potent antagonists with long duration of action in an inhaled animal model of bronchoconstriction. PMID:23099092

Jin, Qi; Davis, Roderick S; Bullion, Ann M; Jin, Jian; Wang, Yonghui; Widdowson, Katherine L; Palovich, Michael R; Foley, James J; Schmidt, Dulcie B; Buckley, Peter T; Webb, Edward F; Salmon, Michael; Belmonte, Kristen E; Sarau, Henry M; Busch-Petersen, Jakob

2012-10-02

322

Biological characterization of Actinobacillus species and Pasteurella ureae.  

PubMed

Forty-seven strains of Actinobacillus and eleven strains of Pasteurella urea were studied using 119 morphological, physiological and biochemical characters. The resulting data were subjected to numerical analysis using the complement of Gower's coefficient excluding negative matches. Clustering was by unweighted pair group average linkage. At distance level 0.30, seven phenons and five isolated strains (including one strain of "A. seminis ") were obtained. The seven phenons correspond to Actinobacillus lignieresii , A. suis, A. equuli , A. capsulatus, "A. salpingitidis ", Actinobacillus sp. (Ross) and P. ureae. The characteristics allowing identification of the seven phenons are tabulated. PMID:6721324

Bercovier, H; Escande, F; Grimont, P A

323

2-Methyl-pyridine-urea (1/1)  

PubMed Central

In the crystal structure of the title compound, C6H7N·CH4N2O, the 2-methyl­pyridine and urea mol­ecules are linked via N—H?O and N—H?N hydrogen bonds, forming ribbons extending along the a axis. The dihedral angle between the 2-methyl­pyridine and urea mean planes is 89.09?(9)°. The methyl group shows rotational disorder wherein the H atoms are located over two sets of sites with equal occupancies.

Ashurov, Jamshid; Ibragimov, Bakhtiyar; Talipov, Samat

2012-01-01

324

Reinvestigation of growth of urea thiosemicarbazone monohydrate crystal  

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

325

Combustion method for simultaneous control of nitrogen oxides and products of incomplete combustion  

Microsoft Academic Search

A method is described for combusting material with controlled generation of both nitrogen oxides and products of incomplete combustion comprising: (A) combusting material in a first combustion zone to produce gaseous exhaust containing products of incomplete combustion and products of complete combustion; (B) passing the gaseous exhaust from the first combustion zone into a second combustion zone having a width

Min-Da

1993-01-01

326

Fuel combustion system and method of operation for an Otto-cycle internal combustion engine  

Microsoft Academic Search

This paper describes a method of combusting a predetermined combustible mixture of fuel and air in an Otto-cycle internal combustion engine including a main combustion chamber, first control valve means for admitting the combustible mixture into the main combustion chamber, an auxiliary combustion chamber, second control valve means for opening and blocking fluid communication between the main combustion chamber and

Bailey

1991-01-01

327

Unsteady spray-group combustion  

SciTech Connect

An unsteady spray combustion formulation is developed for the study of group combustion in axisymmetric spray combustion systems. The focus of the study ia on the interrelation between vaporization, combustion, and transport processes in a spray combustion system and: how these processes affect the transient development and collapse of group combustion structures. The unsteady formulation is targeted to modeling of unsteadiness at convective time scales. The numerical approach chosen is fully implicit in time. The two-space dimension steady state spray combustion computer code developed by Zhou and Chiu (1983) is extended to perform computations with the unsteady model formulation. Microcomputer software is developed to process the large amounts of data generated in an unsteady spray combustion computation into gray scale encoded picture graphic representations of variable values over the combustion field. These gray scale graphic results are employed in the analysis of processes in unsteady spray group combustion mode transitions. The unsteady spray combustion computer code and supporting microcomputer software is used in a case study to assess group combustion mode transitions and cycles brought on by changing inlet droplet number density in a simple cylindrical combustor. These studies identify the stages and mechanisms of formation and dissolution of global group combustion modes and assess the effects on the process and progress of the transitions when mean droplet size, spray angle, or droplet inlet temperature are changed. A brief look at the transient group combustion modes which develop periodically during the cycling of the spray injection process is also presented.

Lottes, S.A.

1989-01-01

328

Urea is a dynamic pool of bioavailable nitrogen in coral reefs  

NASA Astrophysics Data System (ADS)

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

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

2012-03-01

329

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

PubMed

In this work, we investigated in detail the structural characteristics of mixtures of choline chloride and urea with different urea contents by performing molecular dynamic (MD) simulations, and offer possible explanations for the low melting point of the eutectic mixture of choline chloride and urea with a ratio of 1:2. The insertion of urea molecules was found to change the density distribution of cations and anions around the given cations significantly, disrupting the long-range ordered structure of choline chloride. Moreover, with increasing urea concentration, the hydrogen bond interactions between choline cations and Cl(-) anions decreased, while those among urea molecules obviously increased. From the hydrogen bond lifetimes, it was found that a ratio of 1:2 between choline chloride and urea is necessary for a reasonable strength of hydrogen bond interaction to maintain the low melting point of the mixture of choline chloride with urea. In addition, it was also deduced from the interaction energies that a urea content of 67.7 % may make the interactions of cation-anion, cation-urea and anion-urea modest, and thus results in the lower melting point of the eutectic mixture of choline chloride and urea. The present results may offer assistance to some extent for understanding the physicochemical properties of the eutectic mixture of choline chloride and urea, and give valuable information for the further development and application of deep eutectic solvents. PMID:23435478

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

2013-02-23

330

Lean staged combustion assembly  

SciTech Connect

This patent describes a lean staged combustion assembly. It comprises: means for channeling compressed air including a pilot portion and a main portion. This patent also describes an annular combustor outer liner having an upstream end and a downstream end; an annular combustor inner liner having an upstream end and a downstream end and spaced from the outer liner; means for obtaining pilot stage combustion of a fuel-air pilot mixture for generating pilot stage combustion gases between the inner and outer liners using the pilot portion of compressed air channeled to the combustor by the channeling means, a pilot combustor first liner having an upstream end and a downstream end and spaced from the outer liner to define a first pilot combustion zone; a pilot combustor second liner having an upstream end and a downstream end and spaced from the inner liner to define a second pilot combustion zone; circumferentially spaced first fuel injectors and corresponding first air swirlers extending between the first and outer liners at the upstream ends thereof; and circumferentially spaced second fuel injectors and corresponding second air swirlers extending between the second and inner liners at the upstream ends thereof.

Sabla, P.E.; Dodds, W.J.; Tucker, T.M.

1992-03-31

331

Combustion chamber noise suppressor  

SciTech Connect

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

Livingston, A.M.

1986-08-19

332

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.

333

Environmentally conscious coal combustion  

SciTech Connect

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

Hickmott, D.D.; Brown, L.F.; Currier, R.P. [and others

1997-08-01

334

Route Selection Considering Travel Time Variability  

Microsoft Academic Search

Most conventional route guidance systems select the optimal route on the basis of the minimum expected route travel time. However, as a result of the inherent variation in driving conditions, the route travel time that drivers will experience may be longer or shorter than the expected mean travel time. Drivers are likely to have a lower tolerance for experiencing travel

Bruce Hellinga; Liping Fu

335

Multicast Routing in Mobile Ad Hoc Networks  

Microsoft Academic Search

We focus on one critical issue in mobile ad hoc networks that is multicast routing. Advantages and limitations of existing routing protocols are illustrated. Optimal routes, stable links, power conservation, loop freedom, and reduced channel overhead are the main features to be addressed in a more efficient mechanism. In this paper, we propose a new on-demand multicast routing protocol, named

Hasnaa Moustafa; Houda Labiod

2004-01-01

336

Alternative flight route generator by genetic algorithms  

Microsoft Academic Search

This paper presents a new air traffic route generator based on genetic algorithms. Due to traffic growth, direct (and near direct) routes are becoming increasingly congested and there is a real need for spreading traffic on new alternative routes. Those routes have to be different from several operational criteria and must not generate too much extra distance compared to the

Sofiane Oussedik; Daniel Delahaye; Marc Schoenauer

2000-01-01

337

Flights Alternative Routes Generator by Genetic Algorithms  

Microsoft Academic Search

This paper present a new Air Traffic routes gen- erator based on Genetic Algorithms. Due to the traffic growth, direct (and near direct) routes are more and more congested and there is a real need for spreading the traffic on new alternative routes. Those routes have to be differ- ent from several operational criteria and must not gen- erate too

Daniel Delahaye; Marc Schoenauer

2000-01-01

338

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

339

Bandwidth-delay based routing algorithms  

Microsoft Academic Search

Multimedia applications often require guaranteed quality of service and resource reservation, which has raised a number of challenging technical issues for routing. We consider two new routing algorithms based on bandwidth and delay metrics. The implications of routing metrics on path computation are examined and the rationales behind the selection of bandwidth and delay metrics are discussed. Two new routing

Zheng Wang; Jon Crowcroft

1995-01-01

340

Turbulent Combustion Modeling for Turbo-Jet Combustion Chambers.  

National Technical Information Service (NTIS)

The size of the combustion chamber and the operating conditions chosen are taken into account in developing turbulent combustion models for turbojet engines. Premixed and non premixed conditions are discussed in terms of their integration in turbulence mo...

R. Borghi

1990-01-01

341

Internal combustion engine with rotary combustion chamber  

SciTech Connect

This patent describes an internal combustion engine comprising: a block having at least one cylindrical wall surrounding a piston chamber, piston means located in the piston chamber, means operable to reciprocate the piston means in the chamber, head means mounted on the block covering the chamber. The head means having an air and fuel intake passage, an exhaust gas passage, a rotary valve assembly operatively associated with the head means for controlling the flow of air and fuel into the rotary valve assembly and piston chamber and the flow of exhaust gas from rotary valve assembly and the piston chamber, the head means having a housing with a bore open to the piston chamber accommodating the rotary valve assembly. The valve assembly comprising a cylindrical sleeve located in the bore, the sleeve having an inner surface, an ignition hole, and intake and exhaust ports aligned with the intake passage and exhaust gas passage, spark generating means mounted on the housing operable to generate a spark, rotatable valving means located within the sleeve for controlling the flow of air and fuel into the rotary valve assembly and piston chamber and the flow of exhaust gases out of the rotary valve assembly and piston chamber, the rotatable valving means having a valving combustion chamber open to the piston chamber and the inner surface of the sleeve, the rotatable valving means having a valve body. The valving combustion chamber having an inner portion located in the valve body, the valve body having an outer surface spaced from the inner surface of the sleeve segment seal means mounted on the valve body.

Hansen, C.N.; Cross, P.C.

1988-09-27

342

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

Federal Register 2010, 2011, 2012, 2013

...Initiation of Antidumping and Countervailing Duty Administrative Reviews and Deferral of Initiation...See Solid Urea From the Russian Federation: Extension...exists between EuroChem and its franchisees. For...Solid Urea from the Russian...

2011-06-17

343

77 FR 42273 - Solid Urea From the Russian Federation: Preliminary Results of Antidumping Duty Administrative...  

Federal Register 2010, 2011, 2012, 2013

...Initiation of Antidumping and Countervailing Duty Administrative Reviews and Requests for Revocation...See Solid Urea From the Russian Federation: Extension...See Solid Urea from the Russian Federation: Final Results...explaining that price and quantity are not...

2012-07-18

344

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

Code of Federal Regulations, 2012 CFR

... The provisions of this subpart are applicable to the manufacture of urea. Discharges attributable to shipping losses and precipitation runoff from outside the battery limits of the urea manufacturing operations, and cooling tower blowdown are...

2012-07-01

345

Urea denaturation by stronger dispersion interactions with proteins than water implies a 2-stage unfolding  

PubMed Central

The mechanism of denaturation of proteins by urea is explored by using all-atom microseconds molecular dynamics simulations of hen lysozyme generated on BlueGene/L. Accumulation of urea around lysozyme shows that water molecules are expelled from the first hydration shell of the protein. We observe a 2-stage penetration of the protein, with urea penetrating the hydrophobic core before water, forming a “dry globule.” The direct dispersion interaction between urea and the protein backbone and side chains is stronger than for water, which gives rise to the intrusion of urea into the protein interior and to urea's preferential binding to all regions of the protein. This is augmented by preferential hydrogen bond formation between the urea carbonyl and the backbone amides that contributes to the breaking of intrabackbone hydrogen bonds. Our study supports the “direct interaction mechanism” whereby urea has a stronger dispersion interaction with protein than water.

Hua, Lan; Zhou, Ruhong; Thirumalai, D.; Berne, B. J.

2008-01-01

346

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

347

Internal combustion engine squish jet combustion chamber  

SciTech Connect

This patent describes a internal combustion engine block having a piston and cylinder head, one of which has: (a) a substantially cylindrical bowl opening into the face thereof; (b) a pair of squish jet passages having respective inlets communicating with the face thereof, and respective, transversely spaced, outlets directed substantially tangentially into the bowl, the outlet of a first one of the pair being directed upwardly, and the outlet of second one of the pair being directed downwardly from a position above the outlet of the first one, so that a counter-rotating, bilevel swirl can be produced in the bowl by the squish jet outlets.

Evans, R.L.

1986-02-25

348

Simulation of Turbulent Combustion Using Various Turbulent Combustion Models  

Microsoft Academic Search

The reynolds-averaged navier-stokes (RANS) method nowadays still is the major tool for gas turbine chamber (GTC) designers, but there is not a universal method in RANS GTC spray combustion simulation at present especially for the two- phase turbulent combustion. Usually there are two main steps in two-phase combustion: the liquid fuel evaporation and the gas mixture combustion. Thus, two widely

Fang Wang; Yong Huang; Tian Deng

2009-01-01

349

Long-term management of patients with urea cycle disorders  

Microsoft Academic Search

The long-term treatment of patients with urea cycle disorders (UCDs) includes diet treatment and use of specific medications. Guidelines are provided for patients with a severe phenotype. However, treatment must be tailored for each individual, especially with regard to residual enzyme function and in vivo metabolic capacity. This will be reflected in tests used for monitoring therapy that should be

Gerard T. Berry; Robert D. Steiner

2001-01-01

350

Reduction in slow intercompartmental clearance of urea during dialysis  

SciTech Connect

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

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

1985-04-01

351

Prebiotic formation of polyamino acids in molten urea  

NASA Astrophysics Data System (ADS)

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

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

2005-04-01

352

Aryl urea analogs with broad-spectrum antibacterial activity  

Microsoft Academic Search

The preparation and evaluation of novel aryl urea analogs as broad-spectrum antibacterial agents is described. Numerous compounds showed low micromolar minimum inhibitory concentrations (MIC) against both Gram-positive and Gram-negative bacteria. Selected analogs also exhibited in vivo efficacy in a lethal murine model of bacterial septicemia.

Punit P. Seth; Ray Ranken; Dale E. Robinson; Stephen A. Osgood; Lisa M. Risen; Elizabeth L. Rodgers; Michael T. Migawa; Elizabeth A. Jefferson; Eric E. Swayze

2004-01-01

353

Aryl urea analogs with broad-spectrum antibacterial activity.  

PubMed

The preparation and evaluation of novel aryl urea analogs as broad-spectrum antibacterial agents is described. Numerous compounds showed low micromolar minimum inhibitory concentrations (MIC) against both Gram-positive and Gram-negative bacteria. Selected analogs also exhibited in vivo efficacy in a lethal murine model of bacterial septicemia. PMID:15482926

Seth, Punit P; Ranken, Ray; Robinson, Dale E; Osgood, Stephen A; Risen, Lisa M; Rodgers, Elizabeth L; Migawa, Michael T; Jefferson, Elizabeth A; Swayze, Eric E

2004-11-15

354

Dielectric parameters of KDP single crystals added with urea  

Microsoft Academic Search

Potassium dihydrogen orthophosphate (KDP) having superior nonlinear optical properties has been exploited for variety of applications. We have grown KDP single crystals added with urea by the slow evaporation method from aqueous solutions. Dielectric measurements were carried out along both the unique axis and perpendicular directions at various temperatures ranging from 313 to 423 K by the conventional parallel plate capacitor

S. Goma; C. M. Padma; C. K. Mahadevan

2006-01-01

355

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

356

Peptidyl-urea based inhibitors of soluble epoxide hydrolases  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

357

Urea–formaldehyde (UF) adhesive resins for wood  

Microsoft Academic Search

Urea–formaldehyde (UF) resins are the most important type of adhesive resins for the production of wood based panels. They convince by their high reactivity and good performance in the production and by their low price, however they lack in water resistance of the hardened resin owing to the reversibility of the aminomethylene link and hence the susceptibility to hydrolysis. This

M. Dunky

1998-01-01

358

Corrosion testing of urea-formaldehyde foam insulating material  

Microsoft Academic Search

Two tests of the corrosiveness of urea-formaldehyde (UF) foam insulating materials were compared. One test, the Timm test, had test coupons foamed in place. In the second, the Canadian test, blocks of foam already set were placed in contact with test coupons. The Timm test uses 10 gage thick coupons, while the Canadian test specifies 3 mil thick ones. Two

R. Weil; A. Graviano; K. Sheppard

1980-01-01

359

Nitrogen Leaching from Douglas-fir Forests after Urea Fertilization  

Microsoft Academic Search

as urea) and to calculate changes in the N pools of the overstory trees, understory vegetation, and soil. At six sites on production forests in the Hood Canal watershed, Washington, tension lysimeters and estimates of the soil water fl ux were used to quantify the mobilization and leaching of NO 3 -N, NH 4 -N, and dissolved organic nitrogen below

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

2008-01-01

360

Urea-SCR catalyst research and exhaust pipe layout optimization  

Microsoft Academic Search

In this paper, the catalytic converter for SCR have been researched from these respects of carrier, coating and package. A catalyst has been designed based on these characteristics of carrier, coating, package . The reasons for the crystallization of urea in pipe are analyzed, in order to eliminate the crystallization the layout of exhaust pipe is optimized; and the best

Qian Wang; Fangyin Tu; Jun Ma; Hang Xu; Pin Qi; Xiaojing Han

2011-01-01

361

Human Utilization of Urea Nitrogen in Low Calorie Diets  

Microsoft Academic Search

To evaluate the role of calorie intake on the ability of nonprotein nitrogen to substitute for part of a high biological value protein, urea was added to the low caloric milk diets of five obese women during periods of negative nitro gen balance. In five studies, negative nitrogen balance was induced by decreasing milk nitrogen intake to 3.7 g\\/day and

DANIEL LINO GALLINA; ANDJOSE MIGUEL DOMÃ NGUEZ

362

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

363

Combustion inorganic transformations  

SciTech Connect

The overall goal of the project is to develop a unified picture of the physical and chemical changes that occur in coal inorganic matter during combustion. The research is centered on two main tasks. Task 3.2A deals with the use of laser-induced fluorescence spectroscopy (LIFS) to study the release of sodium from various model compounds and coal during combustion in a flame. The vaporized or released sodium is considered to be an important factor in the formation of ash fouling deposits in full-scale utility boilers. Task 3.2B will study changes in the morphology and chemical associations of inorganic components in coals during combustion in a drop-tube furnace designed to simulate the time-temperature profile of a pulverized coal-fired utility boiler. Results are described. 18 refs., 51 figs., 28 tabs.

Benson, S.A.; Sweeny, P.G.; Abrahamson, H.B.; Radonovich, L.J.; Zygarlicke, C.J.; Puffe, W.H.; Maldonado, M.E.

1988-04-01

364

Combustion synthesis of fullerenes  

SciTech Connect

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

Mckinnon, J.T.; Bell, W.L. (TDA Research, Inc., Wheat Ridge, CO (US)); Barkley, R.M. (Cooperative Inst. for Research on Environmental Sciences, Boulder, CO (US))

1992-01-01

365

Sub-combustion chamber of an internal combustion engine  

Microsoft Academic Search

In a cylinder head in an internal combustion engine having a cylinder body to which the cylinder head is installed, with a gasket placed therebetween, the cylinder head is described including a pre-combustion chamber having a cylindrical portion for receiving a ceramic hot plug; and a ceramic hot plug disposed in the cylindrical portion of the pre-combustion chamber. The improvement

Toeda

1987-01-01

366

The Consistent Vehicle Routing Problem  

SciTech Connect

In the small package shipping industry (as in other industries), companies try to differentiate themselves by providing high levels of customer service. This can be accomplished in several ways, including online tracking of packages, ensuring on-time delivery, and offering residential pickups. Some companies want their drivers to develop relationships with customers on a route and have the same drivers visit the same customers at roughly the same time on each day that the customers need service. These service requirements, together with traditional constraints on vehicle capacity and route length, define a variant of the classical capacitated vehicle routing problem, which we call the consistent VRP (ConVRP). In this paper, we formulate the problem as a mixed-integer program and develop an algorithm to solve the ConVRP that is based on the record-to-record travel algorithm. We compare the performance of our algorithm to the optimal mixed-integer program solutions for a set of small problems and then apply our algorithm to five simulated data sets with 1,000 customers and a real-world data set with more than 3,700 customers. We provide a technique for generating ConVRP benchmark problems from vehicle routing problem instances given in the literature and provide our solutions to these instances. The solutions produced by our algorithm on all problems do a very good job of meeting customer service objectives with routes that have a low total travel time.

Groer, Christopher S [ORNL; Golden, Bruce [University of Maryland; Edward, Wasil [American University

2009-01-01

367

Channel routing for VLSI layout  

NASA Astrophysics Data System (ADS)

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

Schory, Michael

1988-12-01

368

Anion Coordination in MetalOrganic Frameworks Functionalized with Urea Hydrogen-Bonding Groups  

Microsoft Academic Search

A series of metal-organic frameworks (MOFs) functionalized with urea hydrogen-bonding groups have been designed, synthesized, and structurally analyzed by single crystal X-ray diffraction to evaluate the efficacy of anion binding within the structural constraints of the MOFs. We found that urea-based functionalities may be used for anion binding within metal-organic frameworks when the tendency for urea???urea self-association is decreased by

Radu Custelcean; Bruce A. Moyer; Vyacheslav Bryantsev; Benjamin P. Hay

2005-01-01

369

Hemodialyzer mass transfer-area coefficients for urea increase at high dialysate flow rates  

Microsoft Academic Search

Hemodialyzer mass transfer-area coefficients for urea increase at high dialysate flow rates. The dialyzer mass transfer-area coefficient (KoA) for urea is an important determinant of urea removal during hemodialysis and is considered to be constant for a given dialyzer. We determined urea clearance for 22 different models of commercial hollow fiber dialyzers (N = ?5\\/model, total N = 107) in

John K Leypoldt; Alfred K Cheung; Lawrence Y Agodoa; John T Daugirdas; Tom Greene; Prakash R Keshaviah; Gerald J Beck

1997-01-01

370

Cluster structure in urea aqueous solution and it's effect on DNA denature  

NASA Astrophysics Data System (ADS)

The existence of large cluster structure in urea aqueous solution is proved by Small Angle Neutron Scattering (SANS). Our results indicate that urea is a water- structure-breaker, and large urea cluster will be formed when it's concentration is higher than 20 w%. This cluster is very stable, and almost do not change with temperature. The helix-to-coil denaturation transition of DNA was studied with various urea concentrations, to testify the solvent structure influence on this process.

Cheng, He; Han, Charles C.; Hammouda, Boualem

2009-03-01

371

Adequacy in hemodialysis: New concepts derived from online urea monitoring1  

Microsoft Academic Search

Adequacy in hemodialysis: New concepts derived from online urea monitoring.BackgroundThe estimation of urea kinetic parameters [urea generation rate (Gu), normalized protein catabolic rate (NPCR), and dialysis dose (Kt\\/V)] is routinely performed during a single hemodialysis session as a representative sample of a stable series. To ascertain whether the stability assumption is tenable and to estimate the variability of urea kinetic

Girolamo Arrigo; Alessandra Beltrame; Giuliano Colasanti

2000-01-01

372

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

373

Alpha-Glucosidase Folding During Urea Denaturation: Enzyme Kinetics and Computational Prediction  

Microsoft Academic Search

In this study, we investigated structural changes in alpha-glucosidase during urea denaturation. Alpha-glucosidase was inactivated\\u000a by urea in a dose-dependent manner. The inactivation was a first-order reaction with a monophase process. Urea inhibited alpha-glucosidase\\u000a in a mixed-type reaction. We found that an increase in the hydrophobic surface of this enzyme induced by urea resulted in\\u000a aggregation caused by unstable folding

Xue-Qiang Wu; Jun Wang; Zhi-Rong Lü; Hong-Min Tang; Sang-Ho Oh; Jong Bhak; Long Shi; Yong-Doo Park; Fei Zou

2010-01-01

374

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

375

Wheel + Ring = Reel: the Impact of Route Filtering on the Stability of Policy Routing  

Microsoft Academic Search

BGP allows providers to express complex routing policies preserving high degrees of autonomy. However, unrestricted routing policies can adversely impact routing stability. A key concept to understand the interplay between autonomy and expressiveness on one side, and stability on the other side, is safety under filtering, i.e., guaranteed stability under autonomous usage of route filters. BGP route filters are used

Luca Cittadini; Giuseppe Di Battista; Massimo Rimondini; Stefano Vissicchio

2009-01-01

376

Wheel + Ring = Reel: The Impact of Route Filtering on the Stability of Policy Routing  

Microsoft Academic Search

Border Gateway Protocol (BGP) allows providers to express complex routing policies preserving high degrees of autonomy. However, unrestricted routing policies can adversely impact routing stability. A key concept to understand the interplay between autonomy and expressiveness on one side, and stability on the other side, is safety under filtering, i.e., guaranteed stability under autonomous usage of route filters. BGP route

Luca Cittadini; Giuseppe Di Battista; Massimo Rimondini; Stefano Vissicchio

2011-01-01

377

An Anonymous On Demand Routing Protocol with Untraceable Routes for Mobile Ad-hoc Networks  

Microsoft Academic Search

In hostile environments, the enemy can launch traffic analys is 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

Jiejun Kong; Xiaoyan Hong; Mario Gerla

378

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

379

Internal combustion chamber  

SciTech Connect

In combination with a high-powered reciprocating piston internal combustion engine, an internal combustion cylinder assembly is described comprising: a cylinder head made of weldable material; a cylinder liner for containing and guiding a reciprocating piston of the engine, a coolant jacket adapted to receive a cooling fluid, mounted on and surrounding the cylinder liner, the jacket being attached to the cylinder head and detachably supported by the cylinder liner, and forming a cooling chamber around the cylinder liner; means to supply the cooling fluid to the cooling chamber and to discharge the cooling fluid therefrom.

Schmitz, D.L.

1988-03-08

380

Thermal ignition combustion system  

DOEpatents

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

Kamo, Roy (Columbus, IN); Kakwani, Ramesh M. (Columbus, IN); Valdmanis, Edgars (Columbus, IN); Woods, Melvins E. (Columbus, IN)

1988-01-01

381

Thermal ignition combustion system  

DOEpatents

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

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

1988-04-19

382

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...

383

Combustible Cartridge Case Ballistic Characterization.  

National Technical Information Service (NTIS)

The combustible cartridge case is widely used in modern ammunition systems. Its mechanical strength allows it to replace metallic packaging in the handling, storage, and loading phases, while its combustible nature eliminates the logistical burden of disp...

F. W. Robbins J. W. Colburn

1990-01-01

384

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

385

Nitrous oxide sampling, analysis, and emission measurements from various combustion systems  

SciTech Connect

Nitrous oxide (N[sub 2]O) emissions from various combustion systems was measured by use of two analytical methods, the performance of which was evaluated together with the sampling procedures. One analytical method is grab sampling followed by analysis by gaschromatography (GC). This procedure was found to give accurate results, provided SO[sub 2] and H[sub 2]O were removed during sampling in order to avoid N[sub 2]O formation in the sample. An evaluation of a continuous infrared N[sub 2]O analyzer shows that it is a useful instrument if measures are taken to eliminate or adjust for interferences from CH[sub 4], SO[sub 2], H[sub 2]O and to a minor extent also from NH[sub 3]. A considerable formation of N[sub 2]O was found when a gas containing SO[sub 2] and NO was scrubbed in a weak acid solution. The sampling program from a variety of combustion systems reveals that N[sub 2]O emissions usually are low (0-5 ppm) from the combustion of pulverized coal. The results from a gas turbine, a laboratory gas-fired fiber burner, and a domestic oil combustor are also in the very low range, whereas emissions from combustion of straw or wood were slightly higher. Even higher emissions were observed from circulating fluidized bed combustion (CFBC), from which the level of emissions increased with decreasing combustion temperature and increasing excess air levels. Sampling inside the CFBC reactor showed that N[sub 2]O formation is particularly rapid at the transition from reducing to oxidizing conditions at the secondary air inlet. Pilot plant experiments with the selective non-catalytic reduction of NO by urea or ammonia resulted in a large increase in N[sub 2]O emissions during the injection of urea, whereas almost no increase was found during the injection of ammonia. 31 refs., 10 figs., 2 tabs.

Hulgaard, T.; Dam-Johansen, K. (Technical Univ. of Denmark, Lyngby (Denmark))

1992-11-01

386

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

387

Synthesis and properties of a novel 2',4'-BNA bearing a urea bridged structure.  

PubMed

Three kinds of novel bridged nucleic acid (BNA) monomers bearing carbamate or urea bridged structures, were designed and synthesized. One of these monomers, a urea-type BNA monomer was successfully incorporated into oligodeoxynucleotides (ODNs), and properties of the ODNs were evaluated. The ODNs containing the urea-type BNA monomers showed RNA selective hybridizing profiles and significant enzymatic stability. PMID:19749235

Yahara, Aiko; Nishida, Masaru; Baba, Takeshi; Kodama, Tetsuya; Imanishi, Takeshi; Obika, Satoshi

2009-01-01

388

Synthesis of Unsymmetrical Diaryl Ureas via Pd-Catalyzed C-N Cross-Coupling Reactions  

PubMed Central

A facile synthesis of unsymmetrical N,N?-diaryl ureas is described. The utilization of the Pd-catalyzed arylation of ureas enables the synthesis of an array of diaryl ureas in good to excellent yields from benzylurea via a one-pot arylation-deprotection protocol, followed by a second arylation.

Breitler, Simon; Oldenhuis, Nathan J.; Fors, Brett P.; Buchwald, Stephen L.

2011-01-01

389

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

Federal Register 2010, 2011, 2012, 2013

...EPA-HQ-OPP-2010-0650; FRL-8855-5] Propionic Acid and Salts, Urea Sulfate, Methidathion, and Methyl...decisions for the pesticides propionic acid and salts, case no. 4078, urea sulfate, case...the table below--propionic acid and salts, case 4078, urea sulfate, case...

2010-12-15

390

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

391

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). 721.10533...721.10533 Amine-modified urea-formaldehyde polymer (generic). (a) Chemical...generically as amine-modified urea-formaldehyde polymer (PMN P-12-182) is...

2013-07-01

392

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

Code of Federal Regulations, 2010 CFR

...Urea-formaldehyde resins in molded articles. 177.1900 Section...Urea-formaldehyde resins in molded articles. Urea-formaldehyde...the food-contact surface of molded articles intended for use in...may be mixed with refined wood pulp and the mixture may...

2009-04-01

393

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

Code of Federal Regulations, 2010 CFR

...Urea-formaldehyde resins in molded articles. 177.1900 Section...Urea-formaldehyde resins in molded articles. Urea-formaldehyde...the food-contact surface of molded articles intended for use in...may be mixed with refined wood pulp and the mixture may...

2010-01-01

394

The Comparative Benefits of the Fractional Excretion of Urea and Sodium in Various Azotemic Oliguric States  

Microsoft Academic Search

Background: The fractional excretion of urea (FeUrea) may result in more reliable in the determination of renal function than sodium in the presence of oliguric azotemia; however, its usefulness remains controversial, perhaps due to an evolving understanding of urea transport within the kidney. Methods: This was a prospective observational study of 100 consecutive patients referred to the nephrology service for

Charles J. Diskin; Thomas J. Stokes; Linda M. Dansby; Lautrec Radcliff; Thomas B. Carter

2010-01-01

395

Cordwood gasification and gas combustion  

Microsoft Academic Search

The purpose of this project was to demonstrate to farmers and potential manufacturing interests a cord wood combustion system for providing thermal energy for curing flue-cured tobacco. Two stage combustion technology which offers advantages of clean and efficient combustion and a modulatable output was utilized. In 1980 a 1.0 GJ\\/h cord wood gasifier-combustor was designed and tested. Two-staged combustion of

1983-01-01

396

Low emission internal combustion engine  

Microsoft Academic Search

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

Karaba; Albert M

1979-01-01

397

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

398

Proceedings of the Combustion Institute. Volume 30  

SciTech Connect

Papers discussed combustion theory and modelling, turbulent combustion, laser diagnostics and control, chemical kinetics, computational combustion, flames, detonations, droplet combustion, catalysis/materials synthesis, pulse detonations engines, diagnosis, engine combustion, heterogeneous combustion, pollutants (PAH and soot), kinetics, flame diagnosis, propulsion, laminar diffusion flames, lifted turbulent flames, nanoparticles, premixed turbulent flames, solid oxide fuel cells, laminar flames, stationary power systems, and plasma supported flames.

NONE

2005-01-15

399

Reversed flow fluidized-bed combustion apparatus  

DOEpatents

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

Shang, Jer-Yu (Fairfax, VA); Mei, Joseph S. (Morgantown, WV); Wilson, John S. (Morgantown, WV)

1984-01-01

400

Impinging air jet combustion apparatus  

Microsoft Academic Search

A combustion liner for a gas turbine combustion apparatus or the like has a head wall and a side wall extending downstream to an outlet for combustion products. A reaction zone is contained within the upstream end of the side wall and a dilution zone downstream. A barrier ring extends inwardly from the side wall to provide a constricted path

J. R. Arvin; A. J. Verdouw

1976-01-01

401

Combustion characteristics of boron nanoparticles  

Microsoft Academic Search

An experimental investigation of the combustion characteristics of boron nanoparticles in the post flame region of a flat flame burner has been conducted. Boron is attractive as a fuel or a fuel supplement in propellants and explosives due to its high heats of combustion on both a gravimetric and volumetric basis. A relatively large database exists for combustion characteristics of

Gregory Young; Kyle Sullivan; Michael R. Zachariah; Kenneth Yu

2009-01-01

402

Combustion Systems for Biomass Fuel  

Microsoft Academic Search

Biomass is one of humanity's earliest sources of energy. Traditionally, biomass has been utilized through direct combustion, and this process is still widely used in many parts of the world. Biomass thermo-chemical conversion investigations are certainly not the most important options at present; combustion is responsible for over 97% of the world's bio-energy production. Biomass combustion is a series of

Ayhan Demirbas

2007-01-01

403

Feed forward combustion control system  

Microsoft Academic Search

A feed forward control system maximizes combustion efficiency in a combustion system, by controlling the amount of excess air supplied to the burner. The feed forward control system includes flow sensors for sensing the flow of air and fuel to the burner. Based upon the fuel flow measurement, a digital computer determines the correct stoichiometric amount of combustion air required

R. C. Hanson; L. C. Hanson

1985-01-01

404

Ventilation effects on combustion products  

Microsoft Academic Search

The effects of fire ventilation on combustion products are expressed in terms of relationship between concentration of products and equivalence ratio, ?. For well-ventilated fires, ? < 1.0, where mostly heat and products of complete combustion (such as CO2 and water) are generated. For ventilation-controlled fires, ? > 1.0, where mostly products of incomplete combustion are generated with very high

A Tewarson

1996-01-01

405

FLAMELESS COMBUSTION AND ITS APPLICATIONS  

Microsoft Academic Search

Flameless Combustion was first developed to suppress thermal NOx formation in burners for heating industrial furnaces using preheated combustion air. While this technique is applied in large numbers now, there are a number of other applications emerging. This presentation will give an introduction into flameless combustion and then show industrial applications and applications which are at a research stage. -

Joachim G. Wünning

406

Light Duty Efficient, Clean Combustion  

Microsoft Academic Search

Cummins has successfully completed the Light Duty Efficient Clean Combustion (LDECC) cooperative program with DoE. This program was established in 2007 in support of the Department of Energy's Vehicles Technologies Advanced Combustion and Emissions Control initiative to remove critical barriers to the commercialization of advanced, high efficiency, emissions compliant internal combustion (IC) engines for light duty vehicles. Work in this

Donald Stanton

2010-01-01

407

Combustion Synthesis of BaCO3 and Its Application for Eu(III) Adsorption From Aqueous Solution  

Microsoft Academic Search

A combustion method using urea as fuel and barium nitrate as oxidant was applied for the synthesis of barium carbonate, which was characterized by XRD, IR, SEM and BET. A batch technique was employed to study the Eu(III) adsorption from an aqueous solution using BaCO3. It was found that the adsorption process attains equilibrium within 3 hours and depends upon

F. Granados-Correa; M. Jiménez-Reyes

2011-01-01

408

Dur3 is the major urea transporter in Candida albicans and is co-regulated with the urea amidolyase Dur1,2  

PubMed Central

Hemiascomycetes, including the pathogen Candida albicans, acquire nitrogen from urea using the urea amidolyase Dur1,2, whereas all other higher fungi use primarily the nickel-containing urease. Urea metabolism via Dur1,2 is important for resistance to innate host immunity in C. albicans infections. To further characterize urea metabolism in C. albicans we examined the function of seven putative urea transporters. Gene disruption established that Dur3, encoded by orf 19.781, is the predominant transporter. [14C]Urea uptake was energy-dependent and decreased approximately sevenfold in a dur3? mutant. DUR1,2 and DUR3 expression was strongly induced by urea, whereas the other putative transporter genes were induced less than twofold. Immediate induction of DUR3 by urea was independent of its metabolism via Dur1,2, but further slow induction of DUR3 required the Dur1,2 pathway. We investigated the role of the GATA transcription factors Gat1 and Gln3 in DUR1,2 and DUR3 expression. Urea induction of DUR1,2 was reduced in a gat1? mutant, strongly reduced in a gln3? mutant, and abolished in a gat1? gln3? double mutant. In contrast, DUR3 induction by urea was preserved in both single mutants but reduced in the double mutant, suggesting that additional signalling mechanisms regulate DUR3 expression. These results establish Dur3 as the major urea transporter in C. albicans and provide additional insights into the control of urea utilization by this pathogen.

Navarathna, Dhammika H. M. L. P.; Das, Aditi; Morschhauser, Joachim; Nickerson, Kenneth W.; Roberts, David D.

2011-01-01

409

ARTICULOS DEL CONO SUR - CHILE Evaluación de la diálisis peritoneal crónica mediante el modelo de cinética de urea 1 Evaluation of chronic peritoneal dialysis using urea kinetic modeling  

Microsoft Academic Search

Objectives: Currently, urea kinetic modeling is routinely accepted to evaluate peritoneal dialysis (PD) through the calculation of Kt\\/V (normalized whole body urea clearence) and nPNA (normalized protein equivalent of total nitrogen appearence). In paediatrics, the exact meaning and target values for these parameters are still under debate. Objective: to evaluate the mean values and correlation between ureaKt\\/V and nutritional parameters

Francisco Cano Sch

2006-01-01

410

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

411

Internal combustion engine  

SciTech Connect

This patent describes an internal combustion engine. It comprises: an engine block, fuel injection means; rotatable shaft means; a wobbler member; a spider assembly; a pair of bearing members; a connecting rod; means for fixing the outer end of each connection rod; means for connecting the inner end of each connecting rod; and lubrication means.

Lacy, J.W.

1991-01-22

412

Lean staged combustion assembly  

Microsoft Academic Search

This patent describes a lean staged combustion assembly. It comprises: means for channeling compressed air including a pilot portion and a main portion. This patent also describes an annular combustor outer liner having an upstream end and a downstream end; an annular combustor inner liner having an upstream end and a downstream end and spaced from the outer liner; means

P. E. Sabla; W. J. Dodds; T. M. Tucker

1992-01-01

413

Auxiliary combustion chamber  

SciTech Connect

An auxiliary combustion chamber is described for an internal combustion engine, the chamber comprises: (a) a chamber liner formed of a ceramic material that is an effective thermal insulator, the chamber liner having substantially hemispherical internal and external surfaces; (b) an outer metal member cast around the chamber liner, the outer member including a substantially hemispherical portion contacting the outer surface of the chamber liner and imparting a compressive stress to the chamber liner; the metal member further includes a substantially cylindrical portion contiguous with the open end of the hemispherical portion and extending beyond the chamber liner; the cylindrical portion has an inner surface of a predetermined inside diameter at ambient temperature; and (c) a substantially cup-shaped nozzle portion formed of a heat-resistant ceramic material and having an orifice disposed in the bottom to provide flow communication from a main combustion chamber to the interior of the auxiliary combustion chamber, the nozzle portion includes a substantially cylindrical outer surface having a diameter greater than predetermined inside diameter of cylindrical portion of the metal member; the nozzle portion is shrink-fit within the cylindrical portion of the outer metal member with the cylindrical outer surface of the ceramic nozzle contacting the inner surface of the cylindrical portion of the metal member. The bottom of the nozzle portion is disposed away from the hemispherical portion of the metal member.

Kawamura, M.; Taniguchi, M.

1987-06-30

414

Combustible dust tests  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

415

Pulse combustion space heater  

Microsoft Academic Search

This patent describes a pulse combustion space heater for heating air in a space to be temperature conditioned. It comprises: a cabinet having exterior walls providing a cabinet volume for enclosing and supporting the heater, interior housing means located within the cabinet volume including walls providing a substantially closed heat transfer chamber having inlet and outlet openings through which air

W. H. Thrasher; C. M. Pavlik; L. Moon

1990-01-01

416

Combustion Synthesis of Nanostructures  

NASA Astrophysics Data System (ADS)

Novel carbon and inorganic 1D nanostructures were prepared by combustion of metal-polytetrafluoroethylene (PTFE) systems in a calorimetric bomb. The high carbon yield from silicon-containing PTFE starting materials is due to the production and volatility of SiF4.

Huczko, A.; Lange, H.; Chojecki, G.; Cudzi??o, S.; Zhu, Y. Q.; Walton, D. R. M.; Kroto, H. W.; Presz, A.; Diduszko, R.

2002-10-01

417

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

PubMed

Gulf toadfish (Opsanus beta) use a unique pulsatile urea excretion mechanism that allows urea to be voided in large pulses via the periodic insertion or activation of a branchial urea transporter. The precise cellular and subcellular location of the facilitated diffusion mechanism(s) remains unclear. An in vitro basolateral membrane vesicle (BLMV) preparation was used to test the hypothesis that urea movement across the gill basolateral membrane occurs through a cortisol-sensitive carrier-mediated mechanism. Toadfish BLMVs demonstrated two components of urea uptake: a linear element at high external urea concentrations, and a phloretin-sensitive saturable constituent (K(m) = 0.24 mmol/l; V(max) = 6.95 micromol x mg protein(-1) x h(-1)) at low urea concentrations (<1 mmol/l). BLMV urea transport in toadfish was unaffected by in vitro treatment with ouabain, N-ethylmaleimide, or the absence of sodium, conditions that are known to inhibit sodium-coupled and proton-coupled urea transport in vertebrates. Transport kinetics were temperature sensitive with a Q(10) > 2, further suggestive of carrier-mediated processes. Our data provide evidence that a basolateral urea facilitated transporter accelerates the movement of urea between the plasma and gills to enable the pulsatile excretion of urea. Furthermore, in vivo infusion of cortisol caused a significant 4.3-fold reduction in BLMV urea transport capacity in lab-crowded fish, suggesting that cortisol inhibits the recruitment of urea transporters to the basolateral membrane, which may ultimately affect the size of the urea pulse event in gulf toadfish. PMID:19458274

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

2009-05-20

418

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

PubMed

The effects of a 6 versus 24h ruminal urea infusion in lactating dairy cows fed a basal diet deficient in N on ruminal ammonia concentration, arterial urea-N concentration, net portal-drained viscera (PDV) urea-N flux, arterial urea-N extraction across the PDV, and renal urea-N kinetics were investigated. Three Danish Holstein cows fitted with ruminal cannulas and permanent indwelling catheters in major splanchnic blood vessels were randomly allocated to a 3 × 3 Latin square design with 21-d periods. Treatments were ventral ruminal infusion of water for 24h (water INF), 24-h infusion of 15 g of urea/kg of dry matter intake (DMI; 24-h INF), and 6-h infusion of 15 g of urea/kg of DMI (6-h INF). The 6-h INF was initiated 0.5h after the afternoon feeding, and ran until 2230 h. Eight sample sets of arterial, portal, and hepatic blood, ruminal fluid, and urine were obtained at 0.5h before the morning feeding and 0.5, 1.5, 2.5, 3.5, 4.5, 5.5, and 6.5h after feeding (i.e., 9 to 15.5h after the 6h infusion was terminated). A substantial decrease in DMI for 6-h INF compared with 24-h INF and water INF was observed, and it has to be recognized that DMI may have confounding effects. However, the experimental setting plan was met (i.e., to cause changes in the daily pattern of ruminal ammonia and blood urea-N concentrations). The arterial urea-N concentration for 24-h INF and 6-h INF were greater than the arterial urea-N concentration with water INF throughout the sampling window. However, the arterial urea-N concentration for 6-h INF decreased steadily with sampling time reflecting a carryover effect from the ruminal urea infusion. The ruminal ammonia concentration and net portal flux of ammonia for 6-h INF were not different from water INF; hence, no carryover effect on ruminal ammonia concentration was observed. The portal flux of urea-N was not affected by treatment (i.e., even the combination of low ruminal ammonia and high arterial urea-N concentration with 6-h INF was not used by the cow to increase the uptake of urea-N across the PDV). Arterial urea-N extraction across the PDV was increased with water INF especially from 0.5 to 3.5h postprandial relative to the urea infusion treatments, reflecting increased epithelial permeability for urea-N. This indicates that daily ruminal peak of ammonia or blood urea-N concentrations overruled potential signals from low ruminal ammonia concentration observed during the sampling window. In conclusion, dairy cows appear unable to increase transport of urea-N from blood to gut in periods with low ruminal ammonia concentrations, even in a situation with infrequent N supply and apparent carryover effects on blood urea-N. It is speculated that mechanisms responsible for downregulation of epithelial urea-N transport based on daily maximum concentrations of ammonia in the rumen or urea-N in the blood suppresses any short-term signal from low ruminal ammonia during periods with low ruminal N supply. PMID:22365222

Røjen, B A; Kristensen, N B

2012-03-01

419

Rethinking iBGP routing  

Microsoft Academic Search

The Internet is organized as a collection of administrative domains, known as Autonomous Systems (ASes). These ASes interact through the Border Gateway Protocol (BGP) that allows them to share reachability information. Adjacent routers in distinct ASes use external BGP (eBGP), whereas in a given AS routes are propagated over internal BGP (iBGP) sessions between any pair of routers. In large

Iuniana M. Oprescu; Mickael Meulle; Steve Uhlig; Cristel Pelsser; Olaf Maennel; Philippe Owezarski

2010-01-01

420

Rethinking iBGP routing  

Microsoft Academic Search

The Internet is organized as a collection of administrative domains, known as Autonomous Systems (ASes). These ASes interact through the Border Gateway Protocol (BGP) that allows them to share reachability information. Adjacent routers in distinct ASes use external BGP (eBGP), whereas in a given AS routes are propagated over internal BGP (iBGP) sessions between any pair of routers. In large

Iuniana M. Oprescu; Mickael Meulle; Steve Uhlig; Cristel Pelsser; Olaf Maennel; Philippe Owezarski

2011-01-01

421

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

422

Origin authentication in interdomain routing  

Microsoft Academic Search

Attacks against Internet routing are increasing in number and severity. Contributing greatly to these attacks is the absence of origin authentication: there is no way to validate claims of address ownership or location. The lack of such services enables not only attacks by malicious entities, but indirectly allow seemingly inconsequential miconfigurations to disrupt large portions of the Internet. This paper

William Aiello; John Ioannidis; Patrick Drew McDaniel

2003-01-01

423

ROFL: routing on flat labels  

Microsoft Academic Search

It is accepted wisdom that the current Internet architecture conates network locations and host identities, but there is no agreement on how a future architecture should distinguish the two. One could sidestep this quandary by routing directly on host identities them- selves, and eliminating the need for network-layer protocols to in- clude any mention of network location. The key to

Matthew Caesar; Tyson Condie; Jayanthkumar Kannan; Karthik Lakshminarayanan; Ion Stoica

2006-01-01

424

Roots/Routes: Part II  

ERIC Educational Resources Information Center

This narrative acts as an articulation of a journey of many routes. Following Part I of the same research journey of rootedness/routedness, it debates the nature of transformation and transcendence beyond personal and political paradoxes informed by neoliberalism and related repressive globalizing discourses. Through a more personal, descriptive,…

Swanson, Dalene M.

2009-01-01

425

A new channel routing problem  

Microsoft Academic Search

In this paper, we present a new model for channel routing. This model generalizes of the model previously studied in the literature. Informally, our model allow the possibility of connecting, for any given net, only some but not all of the pins that belongs to that net. An algorithm for this model was designed and implemented. Experimental results showed that

H. W. Leong; C. L. Liu

1983-01-01

426

Gigabit IP Routing on Raw  

Microsoft Academic Search

Network processors afford a great degree of flexibility to current day routers, yet they still have followed the trend of being largely specialized to the domain of route table look-up. By using a processor architecture that is more gen- eral purpose, routers can gain from economies of scale and increased programmatic flexibility. We propose the use of the Raw Processor

Gleb Chuvpilo; David Wentzlaff; Saman Amarasinghe

2002-01-01

427

Quantifying why urea is a protein denaturant, whereas glycine betaine is a protein stabilizer  

PubMed Central

To explain the large, opposite effects of urea and glycine betaine (GB) on stability of folded proteins and protein complexes, we quantify and interpret preferential interactions of urea with 45 model compounds displaying protein functional groups and compare with a previous analysis of GB. This information is needed to use urea as a probe of coupled folding in protein processes and to tune molecular dynamics force fields. Preferential interactions between urea and model compounds relative to their interactions with water are determined by osmometry or solubility and dissected using a unique coarse-grained analysis to obtain interaction potentials quantifying the interaction of urea with each significant type of protein surface (aliphatic, aromatic hydrocarbon (C); polar and charged N and O). Microscopic local-bulk partition coefficients Kp for the accumulation or exclusion of urea in the water of hydration of these surfaces relative to bulk water are obtained. Kp values reveal that urea accumulates moderately at amide O and weakly at aliphatic C, whereas GB is excluded from both. These results provide both thermodynamic and molecular explanations for the opposite effects of urea and glycine betaine on protein stability, as well as deductions about strengths of amide NH—amide O and amide NH—amide N hydrogen bonds relative to hydrogen bonds to water. Interestingly, urea, like GB, is moderately accumulated at aromatic C surface. Urea m-values for protein folding and other protein processes are quantitatively interpreted and predicted using these urea interaction potentials or Kp values.

Guinn, Emily J.; Pegram, Laurel M.; Capp, Michael W.; Pollock, Michelle N.; Record, M. Thomas

2011-01-01

428

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

429

Effect of urea on the ?-hairpin conformational ensemble and protein denaturation mechanism.  

PubMed

Despite the daily use of urea to influence protein folding and stability, the molecular mechanism with which urea acts is still not well understood. Here the use of combined parallel tempering and metadynamics simulation allows us to study the free-energy landscape associated with the folding/unfolding of ?-hairpin GB1 equilibrium in 8 M urea and pure water. The nature of the unfolded state in both solutions has been analyzed: in urea solution the addition of denaturants acts to expand the denatured state, while in pure water solution the unfolded state is noticeably more compact. For what concerns the mechanism by which urea acts as a denaturant, a preferential direct interaction between urea molecules and protein backbone has been found. However, the bias toward urea solvation is largest at intermediate values of the gyration radius. PMID:21854002

Berteotti, Anna; Barducci, Alessandro; Parrinello, Michele

2011-10-06

430

A Potential Based Routing Protocol for Mobile Ad Hoc Networks  

Microsoft Academic Search

In this paper, we propose a novel proactive routing protocol, referred to as potential management based proactive routing (PMPR), for mobile ad hoc networks. Unlike other proactive routing protocols, PMPR performs request based routing recovery for proactive route maintenance. When a node has lost the routing information, it attempts a local route recovery by broadcasting a request message to neighbor

Dai Yong Kwon; Jae-hwa Chung; Taeweon Suh; Won-gyu Lee; Kyeong Hury

2009-01-01

431

Energy-Efficient Localized Routing in Random Multihop Wireless Networks  

Microsoft Academic Search

A number of energy-aware routing protocols were proposed to seek the energy efficiency of routes in multihop wireless networks. Among them, several geographical localized routing protocols were proposed to help making smarter routing decision using only local information and reduce the routing overhead. However, all proposed localized routing methods cannot guarantee the energy efficiency of their routes. In this paper,

Yu Wang; Xiang-Yang Li; Wen-Zhan Song; Minsu Huang; Teresa A. Dahlberg

2011-01-01

432

Novel symmetrical ureas as modulators of protein arginine methyl transferases.  

PubMed

Methylation of histone arginine residues is an epigenetic mark related to gene expression that is implicated in a variety of biological processes and can be reversed by small-molecule modulators of protein arginine methyltransferases (PRMTs). A series of symmetrical ureas, designed as analogues of the known PRMT1 inhibitor AMI-1 have been synthesized using Pd-catalyzed Ar-N amide bond formation processes or carbonylation reactions as key steps. Their inhibitory profile has been characterized. The enzymatic assays showed a weak effect on PRMT1 and PRMT5 activity for most of the compounds. The acyclic urea that exhibited the strongest effect on the inhibition of the PRMT1 activity also showed the greatest effect on the expression of some androgen receptor target genes (TMPRSS2 and FKBP5), which may be related with its enzymatic activity. Surprisingly, AMI-1 behaved as an activator of PRMT5 activity, a result not reported so far. PMID:23395110

Fontán, Noelia; García-Domínguez, Patricia; Álvarez, Rosana; de Lera, Ángel R

2013-01-22

433

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

NASA Astrophysics Data System (ADS)

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

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

2011-06-01

434

Glycohaemoglobin measurement: methodological differences in relation to interference by urea  

Microsoft Academic Search

The aim of this study was to investigate the agreement between a cation-exchange HPLC method and a boronate affinity method\\u000a 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)\\u000a renal function, and non-diabetic

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

2002-01-01

435

A RAPID AND PRECISE METHOD FOR THE DETERMINATION OF UREA  

PubMed Central

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 volume, reagents, and equipment.

Fawcett, J. K.; Scott, J. E.

1960-01-01

436

Effect of Kapalabhati on blood urea, creatinine and tyrosine.  

PubMed

The present study conducted on twelve normal healthy male subjects showed decrease in blood urea, increase in creatinine and tyrosine after one minute of Kapalabhati, a fast-breathing technique of Hatha Yoga (120 respiratory strokes (min.). From biochemical point of view the practice of Kapalabhati seems to promote decarboxylation and oxidation mechanisms due to which quieting of respiratory centres is achieved, which is also the prerequisite for the practice of Pranayama, another important technique of Yoga. PMID:2399804

Desai, B P; Gharote, M L

1990-06-01

437

Iron oxide-chitosan nanobiocomposite for urea sensor  

Microsoft Academic Search

Urease (Ur) and glutamate dehydrogenase (GLDH) have been co-immobilized onto superparamegnatic iron oxide (Fe3O4) nanoparticles-chitosan (CH) based nanobiocomposite film deposited onto indium-tin-oxide (ITO) coated glass plate via physical adsorption for urea detection. The magnitude of magnetization (60.9emu\\/g) of Fe3O4 nanoparticles (?22nm) estimated using vibrating sample magnetometer (VSM) indicates superparamagnetic behaviour. It is shown that presence of Fe3O4 nanoparticles results in

Ajeet Kaushik; Pratima R. Solanki; Anees A. Ansari; G. Sumana; Sharif Ahmad; Bansi D. Malhotra

2009-01-01

438

Dialysis disequilibrium syndrome (DDS) in the rat: role of the "reverse urea effect".  

PubMed

DDS is characterized by neurologic deterioration and cerebral edema which occurs after hemodialysis. To investigate the pathogenesis of DDDS, we studied the effects of rapid hemodialysis on plasma and brain electrolytes, urea, and osmolality in the rat. Forty-two hours after bilateral nephrectomy, nine uremic rats were hemodialyzed for 90 minutes against dialysate without urea (model of DDS), yielding a decrease in plasma urea from 72 +/- 2 mM to 34 +/- 2 mM (P less than 0.01) and an 8% (29 mOsm/kg) decrease in plasma osmolality. This group was compared to three control groups: 11 uremic animals dialyzed against a bath with urea added so that no fall in plasma urea occurred, and 15 uremic and 12 nonuremic animals that were not dialyzed. In animals dialyzed without urea, compared to uremic non-dialyzed animals, there was a 6% increase in brain water (3.89 +/- 0.04 liter/kg dry wt vs. 3.67 +/- 0.03, P less than 0.01) and an increase in the brain to plasma (urea) ratio (1.30 +/- 0.06 vs. 0.79 +/- 0.05, P less than 0.01). Comparison of these parameters in animals dialyzed without urea versus other control groups yielded similar results. In animals dialyzed without urea, the 53% decrease in plasma urea was associated with only a 13% decrease in brain urea content. Brain content of sodium and potassium was not significantly different among groups. Retention of brain urea despite the large decrease in plasma urea was able to account for the increased brain water observed in animals dialyzed without urea.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:1635345

Silver, S M; DeSimone, J A; Smith, D A; Sterns, R H

1992-07-01

439

State Route 44 from Interstate Route 95 to U.S. Route 1 in New Smyra Beach, Volusia County, Florida.  

National Technical Information Service (NTIS)

The project is for the proposed relocation and reconstruction of State Route 44 from the intersection with Interstate Route 95 eastwardly to the intersection with U.S. Route 1 in the City of New Smyrna Beach, Volusia County, Florida, a distance of 3.5 mil...

1973-01-01

440

Effect of urea on degradation of terbuthylazine in soil.  

PubMed

Pesticide and nitrate contamination of soil and groundwater from agriculture is an environmental and public health concern worldwide. The herbicide terbuthylazine (CBET) has replaced atrazine in Italy and in many other countries because the use of the latter has been banned because of its adverse environmental impacts. Unlike atrazine, knowledge about the fate of CBET in soil is still not extensive, especially regarding its transformation products, but recent monitoring data show its occurrence and that of its main metabolite, desethyl-terbuthylazine (CBAT), in groundwater above the limit of 0.1 microg/L established by European Union Directive and Italian legislation. The objective of this work was to investigate if the presence of the fertilizer urea affects CBET degradation in the soil. Laboratory CBET degradation experiments in the presence/absence of urea were performed with microbiologically active soil and sterilized soil. Terbuthylazine degradation rates under the different experimental conditions were assessed, and the formation, degradation, and transformation of the metabolite CBAT were also studied. Terbuthylazine degradation was affected by the presence of urea, in terms both of a higher disappearance time of 50% of the initial concentration and of a lower amount of CBAT formed. These findings have practical implications for the real-life assessment of the environmental fate of triazine herbicides in agricultural areas since these herbicides are frequently applied to soils receiving ureic fertilizers. PMID:16110979

Caracciolo, Anna Barra; Giuliano, Giuseppe; Grenni, Paola; Cremisini, Carlo; Ciccoli, Roberto; Ubaldi, Carla

2005-05-01

441

Differential stability of the bovine prion protein upon urea unfolding  

PubMed Central

Prion diseases, or transmissible spongiform encephalopathies, are a group of infectious neurological diseases associated with the structural conversion of an endogenous protein (PrP) in the central nervous system. There are two major forms of this protein: the native and noninfectious cellular form, PrPC; and the misfolded, infectious, and proteinase K-resistant form, PrPSc. The C-terminal domain of PrPC is mainly ?-helical in structure, whereas PrPSc in known to aggregate into an assembly of ?-sheets, forming amyloid fibrils. To identify the regions of PrPC potentially involved in the initial steps of the conversion to the infectious conformation, we have used high-resolution NMR spectroscopy to characterize the stability and structure of bovine recombinant PrPC (residues 121 to 230) during unfolding with the denaturant urea. Analysis of the 800 MHz 1H NMR spectra reveals region-specific information about the structural changes occurring upon unfolding. Our data suggest that the dissociation of the native ?-sheet of PrPC is a primary step in the urea-induced unfolding process, while strong hydrophobic interactions between helices ?1 and ?3, and between ?2 and ?3, stabilize these regions even at very high concentrations of urea.

Julien, Olivier; Chatterjee, Subhrangsu; Thiessen, Angela; Graether, Steffen P; Sykes, Brian D

2009-01-01

442

Conformational control of hydrogen-bonded aromatic bis-ureas.  

PubMed

The phenylurea moiety is a ubiquitous synthon in supramolecular chemistry because it contains strong complementary hydrogen bonding groups and is synthetically very accessible. Here we investigate the possibility to strengthen self-association by conformational preorganization of the phenylurea moiety. In fact, we show that it is possible to strongly enhance intermolecular interactions between hydrogen bonded aromatic bis-ureas by substitution at the ortho positions of the phenylurea groups. Ortho substituents enforce a noncoplanar conformation of the urea and phenyl moieties better suited for hydrogen bonding. Substitution by methyl groups is more efficient than with larger groups, probably because of reduced steric hindrance. These effects have been demonstrated in the case of two different supramolecular architectures, which points to the probable generality of the phenomenon. In addition, this study has led to the discovery of a new bis-urea able to form very stable self-assembled nanotubes in toluene up to high temperatures (boiling point) or low concentrations (10(-7) M) and in chloroform down to 3 × 10(-4) M. PMID:22510107

Isare, Benjamin; Pembouong, Gaëlle; Boué, François; Bouteiller, Laurent

2012-05-02

443

Arginine affects urea synthesis in rats treated with thyroid hormone.  

PubMed

The purpose of the present study was to determine whether the regulation of urea synthesis was mediated through the activation of N-acetylglutamate synthesis by arginine and whether the concentration of glutamate or activity of N-acetylglutamate synthetase might control N-acetylglutamate concentration when the thyroid status was manipulated. Three groups of rats were given 6-propyl-2-thiouracil (PTU, thyroid inhibitor) without triiodothyronine (T3) treatment, treated with PTU + T3 or treated with neither PTU nor T3 (control). Urinary excretion of urea, liver concentration of N-acetylglutamate and plasma concentration of arginine in rats given PTU + T3 were significantly lower than in rats given PTU alone. Liver concentration of N-acetyl-glutamate was correlated with plasma concentration of arginine (r = 0.842, P < 0.001). The activity of N-acetylglutamate synthetase and glutamate concentration in liver of the PTU + T3-treated group were significantly higher than in the group treated with PTU alone. Arginine administration (0.5 mmol/100 g body wt) elevated the liver concentration of N-acetylglutamate in all three groups. The results suggest that the greater concentration of arginine in the hypothyroid (PTU alone) rats is likely to increase the N-acetylglutamate concentration and stimulate urea synthesis. PMID:8094095

Hayase, K; Yonekawa, G; Yoshida, A

1993-02-01

444

Vaginal route: a gynaecological route for much more than hysterectomy.  

PubMed

Vaginal hysterectomy is the method of choice for gynaecologists who carry out hysterectomies. Undertaking this procedure regularly will enhance the gynaecologist's level of skill and enable conditions such as ovarian cysts, broad ligament fibroids and other adnexal pathology to be dealt with vaginally during hysterectomy surgery without abdominal invasion. It is also important as the vaginal route allows access to the posterior cul-de-sac, which can facilitate surgery or offer an alternative route to achieving the desired outcome. In this chapter, we look at the main indications for vaginal surgery, and also at other conditions in which vaginal surgery may be suitable (e.g. benign and malignant conditions). We believe that gynaecologists who include vaginal surgery in their armamentarium are better equipped to serve their patients. PMID:21349773

Sheth, Shirish S; Paghdiwalla, Kurush P; Hajari, Anju R

2011-02-23

445

Mössbauer and magnetization studies of nickel ferrite nanoparticles synthesized by the microwave-combustion method  

NASA Astrophysics Data System (ADS)

Nanocrystalline nickel ferrite was synthesized from its stoichiometric metal nitrates and urea mixtures, using a microwave assisted combustion method. The process was a convenient, inexpensive and an efficient method for formation of NiFe2O4 nanomaterials. Effect of urea/metal nitrates ratio on the obtained phases, particle size and magnetic properties has been investigated by various techniques. Saturation magnetization of 50 emu/g was observed at room temperature for larger particles, and it decreases with decreasing particle size. The coercivity attains a maximum value of 170 Oe when the particle size was ~20 nm, and decreases with increasing particle size. Mössbauer spectra measured at RT for some representative samples show a combination of ordered and superparamagnetic behavior, whereas those collected at 20 K elucidate the nature of the obtained phases and cation distribution.

Mahmoud, M. H.; Elshahawy, A. M.; Makhlouf, Salah A.; Hamdeh, H. H.

2013-10-01

446

Heuristic Routing for Solid Waste Collection Vehicles.  

National Technical Information Service (NTIS)

The development and successful application of a heuristic procedure for routing solid waste collection vehicles is described. Topics include (1) the value of routing, (2) reasons for rerouting, (3) advantages of the heuristic approach, (4) heuristic rules...

K. A. Shuster D. A. Schur

1974-01-01

447

Aiming at a general routing strategy  

Microsoft Academic Search

A general method for automatic routing, based on a channel splitting approach, is presented. A weighted graph depicting multilayer partitions and allowing expected channel occupancy estimation is introduced. Problems and algorithms related to the detailed routing phase are briefly reviewed.

J. Heinisch; Honeywell Bull

1981-01-01

448

Progress and Developments of Ocean Weather Routing.  

National Technical Information Service (NTIS)

The present day possibilities of the ocean weather routing of merchant ships were investigated. To this end the feasibility of minimum time ship routing was studied, involving weather forecast uncertainties and ship performance data. The advantages of min...

C. Dewit

1974-01-01

449

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

450

Combustion chamber construction  

SciTech Connect

This patent describes a combustion chamber for use in gas turbine engines is provided with a liner formed of a high temperature material. The liner includes a plurality of annular rings of high temperature material mounted by means of flexible mounting arrangement upon a high strength structural frame. As a result of this mounting arrangement, the liner is substantially isolated from structural forces associated with the combustion chamber, while the frame is substantially isolated from thermal stresses associated with the liner. The individual liner rings may be easily removed for repair or replacement without disassembling the frame and associated components. Furthermore, the decoupling of thermal and structural stresses provides longer life and more dependable operation.

Maclin, H.M.

1989-04-03

451

Combustion chamber construction  

SciTech Connect

A combustion chamber for use in gas turbine engines is provided with a liner formed of a high temperature material. The liner includes a plurality of panels of the material mounted by means of a lost motion mounting arrangement upon a high strength structural frame. As a result of this mounting arrangement, the liner is substantially isolated from structural forces associated with the combustion chamber, while the frame is substantially isolated from thermal stresses associated with the liner. For the purpose of supplying cooling air to the liner panels and frame and cooling air is passed into a plenum to cool the radially outward side of the panels. Transfer means are provided for directing the same air from the plenum to the liner inner surfaces in a cooling film. The liner mounting arrangement disclosed herein is particularly useful with difficult-to-weld liner materials (e.g., oxide dispersion strengthened materials), but its advantages commend its use with other materials also.

Maclin, H.M.

1984-11-06

452

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

453

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

454

Synthesis and properties of degradable poly(urethane urea)s to be used for ligament reconstructions.  

PubMed

In the present study we describe the synthesis, wet spinning, mechanical testing, and degradation of poly(urethane urea)s (PUURs) intended for clinical use in anterior cruciate ligament (ACL) reconstruction. The effects of soft segment chemical composition and molar mass and the kind of diamine chain extender on the material properties were investigated. It was found that the fibers made of PUUR with polycaprolactone diol (PCL530) as soft segment and MDI/1,3-DAP as hard segment (PCL530-3) have high tensile strength and high modulus and when degraded keep their tensile strength for the time demanded for the application. In conclusion, from a chemical and mechanical point of view PUUR fibers of PCL530-3, ARTELON, are suitable for designing a degradable ACL device. PMID:12217040

Gisselfält, Katrin; Edberg, Bengt; Flodin, Per

455

Decoupling policy from mechanism in Internet routing  

Microsoft Academic Search

Routing is a black art in today's Internet. End users and ISPs alike have little control over how their packets are handled outside of their networks, stemming in part from limitations of the current wide-area routing protocol, BGP. We believe that many of these constraints are due to policy-based restrictions on route-exportation. Separating forwarding policy from route discovery would allow

Alex C. Snoeren; Barath Raghavan

2004-01-01

456

Source selectable path diversity via routing deflections  

Microsoft Academic Search

We present the design of a routing system in which end-systems set tags to select non-shortest path routes as an alternative to explicit source routes. Routers collectively generate these routes by using tags as hints to independently deflect packets to neighbors t hat lie off the shortest-path. We show how this can be done simply, by local extensions of the

Xiaowei Yang; David Wetherall

2006-01-01

457

Overview of QoS Routing  

Microsoft Academic Search

Abstract QoS routing has been recognized as an important part in the evolution of QoS service offerings in the network. The goal of routing solutions is twofold: (1) satisfying the QoS requirements for every admitted connection, and (2) achieving global efficiency in resource utilization [1]. This paper describes some of QoS-based routing issues and requirements, and presents different routing strategies,

Bin Deng; Hao Liu; Minghua Zheng

458

Fault-tolerant wormhole routing in tori  

Microsoft Academic Search

We present a method to enhance wormhole routing algorithms for deadlock-free fault-tolerant routing in tori. We consider arbitrarily-located faulty blocks and assume only local knowledge of faults. Messages are routed via shortest paths when there are no faults, and this constraint is only slightly relaxed to facilitate routing in the presence of faults. The key concept we use is that,

Suresh Chalasani; Rajendra V. Boppana

1994-01-01

459

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

460

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

461

Urea for Lactating Dairy Cattle. III. Nutritive Value of Rations of Corn Silage Plus Concentrate Containing Various Levels of Urea[1] and [2  

Microsoft Academic Search

Four mature Holstein cows were used simultaneously in a 4 X 4 Latin-square design (balanced for residual effects) to evaluate rations containing various pro- portions of concentrate urea. Corn silage was fed ad libitnm as the sole forage. All concentrates were isocalo,rie and isoni- trogenous, each containing the same amounts of every ingredient except soybean oil meal, urea, and hominy.

J. B. Holter; N. F. Colovos; H. A. Davis; W. E. Urban Jr.

1968-01-01

462

Ammonia and urea excretion in the tidepool sculpin ( Oligocottus maculosus ): sites of excretion, effects of reduced salinity and mechanisms of urea transport  

Microsoft Academic Search

Tidepool sculpins live in a variable environment where water temperature, salinity, gas tensions, and pH can change considerably with the daily tide cycle. Tidepool sculpins are primarily ammoniotelic, with 8–17% of nitrogen wastes excreted as urea. The majority of net ammonia (Jnetamm; 85%) and urea (Jneturea; 74%) excretion occurred across the gill, with the remainder excreted across the skin, the

P. A. Wright; P. Part; C. M. Wood

1995-01-01

463

Completing high-quality global routes  

Microsoft Academic Search

To ensure chip manufacturability, all routes must be completed without violations. Furthermore, the chip's power consumption and performance are determined by the length of its routed wires. Therefore, our work focuses on minimizing wirelength. Our key innovations include: (1) a novel branch-free representation (BFR) for routed nets, (2) a trigonometric penalty function (TPF), (3) dynamic adjustment of Lagrange multipliers (DALM),

Jin Hu; Jarrod A. Roy; Igor L. Markov

2010-01-01

464

MARTEL'S ROUTES IN MAMMOTH CAVE, KENTUCKY, 1912  

Microsoft Academic Search

SUMMARY Martel's own copy of the Hovey 1912 guidebook to Mammoth Cave has his routes marked faintly in pencil on the printed cave plans. These plans are reproduced here, with his routes indicated on them. He generally followed the four standard tourist routes which now includ- ed Kaemper's 1908 discoveries to Violet City, but instead of visiting the Maelstrom he

Trevor R. SHAW

465

How much can taxes help selfish routing?  

Microsoft Academic Search

We study economic incentives for influencing selfish behavior in networks. We consider a model of selfish routing in which the latency experienced by network traffic on an edge of the network is a function of the edge congestion, and network users are assumed to selfishly route traffic on minimum-latency paths. The quality of a routing of traffic is historically measured

Richard Cole; Yevgeniy Dodis; Tim Roughgarden

2003-01-01

466

On characterizing BGP routing table growth  

Microsoft Academic Search

The sizes of the BGP routing tables have increased by an order of magnitude over the last six years. This dramatic growth of the routing table can decrease the packet forwarding speed and demand more router memory space. In this paper, we explore the extent that various factors contribute to the routing table size and characterize the growth of each

Tian Bu; Lixin Gao; Donald F. Towsley

2004-01-01

467

Gossip-based ad hoc routing  

Microsoft Academic Search

Many ad hoc routing protocols are based on (some variant of) flooding. Despite various optimizations, many routing messages are propagated unnecessarily. We propose a gossiping-based approach, where each node for- wards a message with some probability, to reduce the over- head of the routing protocols. Gossiping exhibits bimodal behavior in sufficiently large networks: in some executions, the gossip dies out

Zygmunt J. Haas; Joseph Y. Halpern; Erran L. Li

2002-01-01

468

Gossip-based ad hoc routing  

Microsoft Academic Search

Abstract: Many ad hoc routing protocols are based on some variant offlooding. Despite various optimizations, many routing messages are propagatedunnecessarily. We propose a gossiping-based approach, where eachnode forwards a message with some probability, to reduce the overhead ofthe routing protocols. Gossiping exhibits bimodal behavior in sufficientlylarge networks: in some executions, the gossip dies out quickly and hardlyany node gets the

Zygmunt J. Haas; Joseph Y. Halpern; Li Li

2006-01-01

469

The case for separating routing from routers  

Microsoft Academic Search

Over the past decade, the complexity of the Internet's routing infrastructure has increased dramatically. This complexity and the problems it causes stem not just from various new demands made of the routing infrastructure, but also from fundamental limitations in the ability of today's distributed infrastructure to scalably cope with new requirements.The limitations in today's routing system arise in large part

Nick Feamster; Hari Balakrishnan; Jennifer Rexford; Aman Shaikh; Jacobus van der Merwe

2004-01-01

470

Risk assessment of alternative proliferation routes  

Microsoft Academic Search

Multi-Attribute Decision Theory is applied to rank II alternative routes to nuclear proliferation in order of difficulty in acquiring nuclear weapons by nonnuclear countries. The method is based on reducing the various variables affecting the decision to a single function providing a measure for the proliferation route. The results indicate that the most difficult route to obtain atomic weapons is

S. Ahmed; A. A. Husseiny

1982-01-01

471

Modeling environments from a route perspective  

Microsoft Academic Search

Environment attributes are perceived or remembered differently according to the perspective used. In this study, two different perspectives, a survey perspective and a route perspective, are explained and discussed. This paper proposes an approach for modeling human environments from a route perspective, which is the perspective used when a human navigates through the environment. The process for route perspective semi-autonomous

Luis Yoichi Morales Saiki; Satoru Satake; Takayuki Kanda; Norihiro Hagita

2011-01-01

472

Stable internet routing without global coordination  

Microsoft Academic Search

The Border Gateway Protocol (BGP) allows an autonomous system (AS) to apply diverse local policies for selecting routes and propagating reachability information to other domains. However, BGP permits ASs to have conflicting policies that can lead to routing instability. This paper proposes a set of guidelines for an AS to follow in setting its routing policies, without requiring coordination with

Lixin Gao; Jennifer Rexford

2001-01-01

473

Stable Internet routing without global coordination  

Microsoft Academic Search

The Border Gateway Protocol (BGP) allows an autonomous system (AS) to apply diverse local policies for selecting routes and propagating reachability information to other domains. However, BGP permits ASes to have conflicting policies that can lead to routing instability. This paper proposes a set of guidelines for an AS to follow in setting its routing policies, without requiring coordination with

Lixin Gao; Jennifer Rexford

2000-01-01

474

Inherently Safe Backup Routing with BGP  

Microsoft Academic Search

IP routing requires the cooperation of a large number of Autonomous Systems (ASes) via the Border Gateway Protocol (BGP). Each AS applies lo- cal policies for selecting routes and propagating routes to others, with important implications for the reliability and stability of the global system. In and of itself, BGP does not ensure that every pair of hosts can communi-

Lixin Gao; Timothy Griffin; Jennifer Rexford

2001-01-01

475

HARP - HYBRID AD HOC ROUTING PROTOCOL  

Microsoft Academic Search

This paper presents a bandwidth- efficient low-delay routing protocol for mobile ad hoc networks called HARP - hybrid ad hoc rout- ing protocol. HARP is a hybrid scheme combin- ing reactive and proactive approaches. The routing is performed on two levels: intra-zone and inter- zone, depending on whether the destination be- longs to the same zone as the forwarding node.

Navid Nikaein; Christian Bonnet; Neda Nikaein

476

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

477

An emergency response mobile robot for operations in combustible atmospheres  

NASA Astrophysics Data System (ADS)

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

Stone, Henry W.; Ohm, Timothy R.

1993-11-01

478

Nitrous oxide emissions from fossil-fuel combustion  

SciTech Connect

The role of coal combustion as a significant global source of nitrous oxide (N2O) emissions was reexamined through on-line emission measurements from six pulverized-coal-fired utility boilers and from laboratory and pilot-scale combustors. The full-scale utility boilers yielded direct N2O emission levels of less than 5 ppm. The sub-scale combustor test data were consistent with full-scale data, and also showed N2O emission levels not exceeding 5 ppm, although these levels increased slightly when various combustion modifications to lower NO emissions were employed. These on-line emission measurements are very different from previously published data. The discrepancy is shown to be due to a sampling artifact by which significant quantities of N2O can be produced in sample containers which have been used in establishing the prevously employed N2O data base. Consequently, it was concluded that N2O emissions bear no direct relationship to NO emissions from these combustion sources, and that the direct source of N2O is negligible. Other indirect routes for the conversion of NO into N2O outside the combustor and other combustion sources not examined by the study, however, cannot be ruled out. (Copyright (c) 1990 by the American Geophysical Union.)

Linak, W.P.; McSorley, J.A.; Hall, R.E.; Ryan, J.V.; Wendt, J.O.L.

1990-01-01

479

An EnergyBalance Multipath Routing Based on Rumor Routing for Wireless Sensor Networks  

Microsoft Academic Search

These nodes have limited energy supply in wireless sensor networks. Thus energy consumption is the main concern while developing routing algorithm in wireless sensor networks. In this paper, we propose a multi-path routing algorithm based on Rumor Routing, called EBMRR (Energy-Balance Multipath Rumor Routing), which is probabilistic approach that attempts to find multipath according to residual energy and energy usage

Lu Hong; Jing Yang

2009-01-01

480

Arctic routing: Challenges and opportunities  

Microsoft Academic Search

Responding to the world’s growing demand for oil and gas, Arctic resources have been given much attention by the energy and\\u000a shipping industries. In addition, global warming has accelerated oil and gas development in the Arctic, particularly in its\\u000a western region. Ice-diminishing Arctic has inspired the world’s shipping industry to explore the feasibility of the historical\\u000a Arctic routes, the Northwest

Hiromitsu Kitagawa

2008-01-01

481

Airy beam induced optical routing  

NASA Astrophysics Data System (ADS)

We present an all-optical routing scheme based simultaneously on optically induced photonic structures and the Airy beam family. The presented work utilizes these accelerating beams for the demonstration of an all-optical router with individually addressable output channels. In addition, we are able to activate multiple channels at the same time providing us with an optically induced splitter with configurable outputs. The experimental results are corroborated by corresponding numerical simulations.

Rose, Patrick; Diebel, Falko; Boguslawski, Martin; Denz, Cornelia

2013-03-01

482

Routing in Wireless Sensor Networks  

Microsoft Academic Search

\\u000a Wireless sensor networks are formed by small sensor nodes communicating over wireless links without using a fixed network\\u000a infrastructure. Sensor nodes have a limited transmission range, and their processing and storage capabilities as well as their\\u000a energy resources are also limited. Routing protocols for wireless sensor networks have to ensure reliable multi-hop communication\\u000a under these conditions. We describe design challenges

Hannes Frey; Stefan Rührup; Ivan Stojmenovi?

483

Routing in Extremely Mobile Networks  

Microsoft Academic Search

To become realistically untethered, wireless communication networks need to be self-organised, rapidly deployable, infrastructureless\\u000a and mobile. Existing protocols are efficient in routing data dynamically between mobile nodes that belong to the same connected\\u000a component. Concrete applications such as Defence and Disaster-Relief cannot always assume that the network is connected (i.e., not partitionned). However, even if the network is continuously partitioned,

Géraud Allard; Philippe Jacquet; Bernard Mans

484

ENSURING THE AVAILABILITY AND RELIABILITY OF UREA DOSING FOR ON-ROAD AND NON-ROAD  

SciTech Connect

The purpose of this presentation is to address two important issues. The first issue is nationwide availability of urea. The second is assurance by the engine maker that the engine cannot operate without urea. In regard to the first issue, North American urea production can support SCR needs for the Heavy Duty truck industry. The existing distribution methods, pathways and technology could be utilized for urea supply with no new invention required. Urea usage and storage capacity on vehicles would support long distances between tank refills, as SCR could be initially rolled out with a limited infrastructure. The price of urea should be less than diesel fuel and urea SCR should have a fuel economy advantage over competing technologies. It can be in place by 2007. In regard to the second issue, sensor technology exists to monitor urea tank level and verify that the fluid in the tank is urea. NOx sensors are available to monitor tailpipe NOx, ensuring the entire SCR system is functioning properly, and inferring that urea is in the system. The monitoring system could be used to monitor compliance, record faults, and initiate enforcement actions as necessary. The monitoring system could initiate actions to encourage compliance.

Barton, G; Lonsdale, B

2003-08-24

485

Analysis of the stability of urea in dried blood spots collected and stored on filter paper.  

PubMed

The ability to use dry blood spots (DBSs) on filter paper for the analysis of urea levels could be an important diagnostic tool for areas that have limited access to laboratory facilities. We developed a method for the extraction and quantification of urea from DBSs that were stored on 3M Whatman filter paper and investigated the effect of long-term storage on the level of urea in DBSs. DBSs of 4.5 mm in diameter were used for our assay, and we determined the urea levels in blood using a commercially available enzymatic kit (UV GLDH-method; Randox laboratories Ltd., UK). The DBSs on filter discs were stored at 4? or at 37? for 120 days. The mean intra- and inter-assay coefficient of variance for our method of urea extraction from dried blood was 4.2% and 6.3%, respectively. We collected 75 fresh blood samples and compared the urea content of each fresh sample with the urea content of DBSs taken from corresponding fresh blood samples. Regression analysis reported a regression coefficient (r) value of 0.97 and a recovery of urea from dried spots was 102.2%. Urea concentrations in DBSs were stable for up to 120 and 90 days when stored at 4? and 37?, respectively. Our results show that urea can be stored and quantitatively recovered from small volumes of blood that was collected on filter paper. PMID:23667845

Quraishi, Rizwana; Lakshmy, Ramakrishnan; Mukhopadhyay, Ashok Kumar; Jailkhani, Bansi Lal

2013-04-17

486

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

487

Synergistic behavior of glycine betaine-urea mixture: A molecular dynamics study.  

PubMed

Glycine betaine (GB) is one of the most important osmolyte which is known to stabilize proteins as well as counteract the denaturing effect of urea. There have been many studies indicating protein stabilization and counteraction of the effect of urea by GB. However, the exact mechanism of counteraction is still debated and is of important research interest. In this study, distribution functions, hydrogen bonds, and energetics were analysed to understand different interactions between GB and urea, and their solvation properties in presence of each other. The results show that in the GB-urea mixture, GB acted as a stronger osmolyte and urea became a weaker denaturing agent than its individual counterparts. The increase in the solvation of urea and GB in GB-urea mixture and their mutual interactions through hydrogen bonding and coulombic energy resulted in more involvement of GB and urea with solvent as well as with themselves. This might result in the increase of the exclusion of GB from protein surface and decrease in the protein-urea interactions in the mixture. This synergistic behavior might be the prime reason for the counteraction of denaturing effect of urea by GB. PMID:24070312

Kumar, Narendra; Kishore, Nand

2013-09-21

488

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

489

Analysis of the Stability of Urea in Dried Blood Spots Collected and Stored on Filter Paper  

PubMed Central

The ability to use dry blood spots (DBSs) on filter paper for the analysis of urea levels could be an important diagnostic tool for areas that have limited access to laboratory facilities. We developed a method for the extraction and quantification of urea from DBSs that were stored on 3M Whatman filter paper and investigated the effect of long-term storage on the level of urea in DBSs. DBSs of 4.5 mm in diameter were used for our assay, and we determined the urea levels in blood using a commercially available enzymatic kit (UV GLDH-method; Randox laboratories Ltd., UK). The DBSs on filter discs were stored at 4? or at 37? for 120 days. The mean intra- and inter-assay coefficient of variance for our method of urea extraction from dried blood was 4.2% and 6.3%, respectively. We collected 75 fresh blood samples and compared the urea content of each fresh sample with the urea content of DBSs taken from corresponding fresh blood samples. Regression analysis reported a regression coefficient (r) value of 0.97 and a recovery of urea from dried spots was 102.2%. Urea concentrations in DBSs were stable for up to 120 and 90 days when stored at 4? and 37?, respectively. Our results show that urea can be stored and quantitatively recovered from small volumes of blood that was collected on filter paper.

Lakshmy, Ramakrishnan; Mukhopadhyay, Ashok Kumar; Jailkhani, Bansi Lal

2013-01-01

490

Synergistic behavior of glycine betaine-urea mixture: A molecular dynamics study  

NASA Astrophysics Data System (ADS)

Glycine betaine (GB) is one of the most important osmolyte which is known to stabilize proteins as well as counteract the denaturing effect of urea. There have been many studies indicating protein stabilization and counteraction of the effect of urea by GB. However, the exact mechanism of counteraction is still debated and is of important research interest. In this study, distribution functions, hydrogen bonds, and energetics were analysed to understand different interactions between GB and urea, and their solvation properties in presence of each other. The results show that in the GB-urea mixture, GB acted as a stronger osmolyte and urea became a weaker denaturing agent than its individual counterparts. The increase in the solvation of urea and GB in GB-urea mixture and their mutual interactions through hydrogen bonding and coulombic energy resulted in more involvement of GB and urea with solvent as well as with themselves. This might result in the increase of the exclusion of GB from protein surface and decrease in the protein-urea interactions in the mixture. This synergistic behavior might be the prime reason for the counteraction of denaturing effect of urea by GB.

Kumar, Narendra; Kishore, Nand

2013-09-01