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1

Urea reduction of NO\\/sub x\\/ in combustion effluents  

Microsoft Academic Search

Method is claimed for reducing NO\\/sub x\\/ in combustion effluents by introducing urea at elevated temperatures in the presence of oxygen, either as a solid or solution in amounts sufficient to reduce the NO\\/sub x\\/ concentration. Conveniently, the urea may be introduced as a solid powder or as a solution in a hydroxylic solvent, at temperatures in excess of 1300°

J. K. Arand; L. J. Muzio; J. G. Sotter

1980-01-01

2

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

3

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

4

Synthesis of alumina powder by the urea-glycine-nitrate combustion process: a mixed fuel approach to nanoscale metal oxides  

NASA Astrophysics Data System (ADS)

Main objective of present work is to study the efficiency of mixed fuel towards solution combustion synthesis of alumina powder, which otherwise prepared by single fuel and study of properties of final product with mixed fuel approach. Two different fuels, glycine and urea, along with aluminium nitrates have been used to prepare nanophase alumina powder. Different fuel to oxidizer ratios and different percentage combination of two fuels were used to prepare six samples. In all samples, nanoscale particle size obtained. Parameter which continuously changes the results of various characterisations is percentage combination of two fuels. In case where percentage of urea is higher than glycine reaction takes place with high exothermicity and hence crystallinity in product phase, whereas glycine promotes amorphous character. With mixed fuel approach, crystallinity can be enhanced easily, by calcinations of powder product at low temperature, because due to mixed urea and glycine, there is already some fraction of crystallinity observed. Overall mixed fuel approach has ability to produce nanophase alumina powder with wide range of particles size.

Sharma, Amit; Rani, Amita; Singh, Ajay; Modi, O. P.; Gupta, Gaurav K.

2014-03-01

5

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

6

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

SciTech Connect

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

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

2006-05-25

7

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

8

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

SciTech Connect

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

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

2012-03-15

9

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

10

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

SciTech Connect

The 'Freedom Car' Initiative announced by the Bush Administration has placed a significant emphasis on development of a hydrogen economy in the United States. While the hydrogen-fueled fuel-cell vehicle that is the focus of the 'Freedom Car' program would rely on electrochemical energy conversion, and despite the large amount of resources being devoted to its objectives, near-term implementation of hydrogen in the transportation sector is not likely to arise from fuel cell cars. Instead, fuel blending and ''hydrogen-assisted'' combustion are more realizable pathways for wide-scale hydrogen utilization within the next ten years. Thus, a large potential avenue for utilization of hydrogen in transportation applications is through blending with natural gas, since there is an existing market for natural-gas vehicles of various classes, and since hydrogen can provide a means of achieving even stricter emissions standards. Another potential avenue is through use of hydrogen to 'assist' diesel combustion to permit alternate combustion strategies that can achieve lower emissions and higher efficiency. This project focused on developing the underlying fundamental information to support technologies that will facilitate the introduction of coal-derived hydrogen into the market. Two paths were envisioned for hydrogen utilization in transportation applications. One is for hydrogen to be mixed with other fuels, specifically natural gas, to enhance performance in existing natural gas-fueled vehicles (e.g., transit buses) and provide a practical and marketable avenue to begin using hydrogen in the field. A second is to use hydrogen to enable alternative combustion modes in existing diesel engines, such as homogeneous charge compression ignition, to permit enhanced efficiency and reduced emissions. Thus, this project on hydrogen-assisted combustion encompassed two major objectives: (1) Optimization of hydrogen-natural gas mixture composition and utilization through laboratory studies of spark-ignition engine operation on H{sub 2}-NG and numerical simulation of the impact of hydrogen blending on the physical and chemical processes within the engine; and (2) Examination of hydrogen-assisted combustion in advanced compression-ignition engine processes. To that end, numerical capabilities were applied to the study of hydrogen assisted combustion and experimental facilities were developed to achieve the project objectives.

Andre Boehman; Daniel Haworth

2008-09-30

11

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

12

Combustion  

NASA Technical Reports Server (NTRS)

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

Bulzan, Dan

2007-01-01

13

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.

2014-01-28

14

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

15

Xenobiotic-urea conjugates; chemical or biological?  

PubMed

Abstract 1.?Although the major pathways involved in drug metabolism have been elucidated, there remain those routes that may be considered as minor, esoteric, or even artifactual. 2.?Conjugation with urea, an abundant, non-toxic, small water soluble molecule, is such a disputed and debatable Phase II pathway. 3.?The present article collates data gleaned from the literature concerning xenobiotic-urea conjugation, presents pertinent information resurrecting the controversy and poses questions as to the nature of the phenomenon. PMID:25144804

Mitchell, Stephen C

2014-12-01

16

SOURCE ASSESSMENT: UREA MANUFACTURE  

EPA Science Inventory

The report gives results of an evaluation of the potential environmental effects of air emissions from the production of urea. Urea production in the U.S. was 3.45 million metric tons in 1975. Major products were urea solution (38%), granulated solid material (53%), and prilled s...

17

Biohydrolysis of urea from urea-bearing wastewater.  

PubMed

Biological stabilization of urea is a two staged process; (i) urea hydrolysis and (ii) ammonia stripping/nitrification-denitrification. Ammonia thus produced is either stripped off by usual methods or after converting into nitrate using chemoautotrophic bacteria. On denitrification, nitrate is finally converted into nitrogen gas by means of heterotrophic bacteria. Details of stabilization of urea from urea bearing wastewater using urea biohydrolyser are presented in this paper. PMID:14672371

Pathe, Pradhyumna P; Tapas, Nandy; Kaul, Santosh N; Deshpande, Chandrasekhar V; Szpyrkowicz, Lidia

2003-01-01

18

Flash synthesis of Li2TiO3 powder by microwave-induced solution combustion  

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

19

Routing Protocols Hierarchical Routing  

E-print Network

dest's in routing tables! · routing table exchange would swamp links! administrative autonomy Hierarchical Routing · aggregate routers into regions, "autonomous systems" (AS) · routers in same AS run same this reachability AS1 needs: 2. to learn which dests are reachable through AS2 and which through info to all routers

Campbell, Andrew T.

20

Nanocrystalline pirochromite spinel through solution combustion synthesis  

Microsoft Academic Search

The production of magnesium–chromium oxides by solution combustion synthesis was investigated using glycine and urea for the first time. Ammonium dichromate, urea\\/glycine and ammonium nitrate aqueous solutions were used as the precursors of the oxides. The effect of different reaction parameters, such as fuel richness, stoichiometry and fuel leanness was evaluated; such parameters were modified by changing the reagents and

M. J. de Andrade; M. D. Lima; R. Bonadiman; C. P. Bergmann

2006-01-01

21

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

22

Chemiresistor urea sensor  

DOEpatents

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

Glass, R.S.

1997-12-16

23

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

SciTech Connect

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

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

2009-04-02

24

Urea and amphibian water economy.  

PubMed

Accumulation of urea in the body fluids enables some amphibians to tolerate high ambient salinities (Bufo viridis, Xenopus laevis, Rana cancrivora, Ambystoma tigrinum, Batrachoseps spp.) or to estivate in soil with low water potentials (Scaphiopus spp.). These species are assumed not only to accumulate urea produced in the normal metabolism, but to synthesize urea in response to water shortage. Re-examination of the data did not support the view of an osmoregulatory urea synthesis. Increased urea synthesis on exposure to high salinities in X. laevis, R. cancrivora and Batrachoseps spp. seemed to reflect reactions to an adverse environment. It is suggested that in amphibians, solute concentration in the plasma and rate of excretion of urea are coordinated so that at a certain plasma concentration, urea is excreted at the same rate at which it is produced. The higher the level of urea in the body fluids at balance between production and excretion, the higher the tolerance of the species of low external water potentials. The mechanisms that integrate the relationship between plasma solute concentration and handling of urea by the kidneys are not known. PMID:9172374

Jørgensen, C B

1997-06-01

25

Computer Routing.  

ERIC Educational Resources Information Center

Computerized bus-routing systems plot the most efficient routes, cut the time it takes to draw routes, and generate reports quickly and accurately. However, school districts often underestimate the amount of work necessary to get information into the computer database. (MLF)

Malone, Roger

1991-01-01

26

Combustion synthesis of thoria – a feasibility study  

Microsoft Academic Search

In an effort to prepare a thoria powder feed that can be compacted and sintered at lower temperatures, the feasibility of the combustion synthesis was studied. Here, preparations using thorium nitrate as oxidant and urea or citric acid as fuel were studied. The powders thus prepared were characterized for surface area and crystallite size and were compacted into pellets and

V. Chandramouli; S. Anthonysamy; P. R. Vasudeva Rao

1999-01-01

27

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

28

Relative efficiency of prilled urea and urea-supergranules in Java citronella ( Cymbopogon winterianus Jowitt)  

Microsoft Academic Search

A two-year field study was carried out to compare the efficiency of prilled urea and urea-supergranules in the cultivation of a perennial aromatic grass, citronella (Cymbopogon winterianus Jowitt) in a sandy loam soil. Application of 300kg Nha-1 year-1 increased the herb and essential oil yields. Urea-supergranules significantly increased the yields over prilled urea.

EVS Prakasa Rao; Munnu Singh; Narayana; G Chandrasekhara

1984-01-01

29

Phytotoxicity of foliar-applied urea  

PubMed Central

Recent work in our laboratory showed that the adverse effect of urea fertilizer on seed germination and seedling growth in soil is due to ammonia produced through hydrolysis of urea by soil urease (NH2CONH2 + H2O ? 2NH3 + CO2) and can be eliminated by amending the fertilizer with a small amount of a urease inhibitor such as phenylphosphorodiamidate. Because the leaf-tip necrosis often observed after foliar fertilization of plants with urea is usually attributed to ammonia formed through hydrolysis of urea by plant urease, we studied the possibility that this necrosis could be eliminated or reduced by adding phenylphosphorodiamidate to the urea fertilizer. We found that, although addition of this urease inhibitor to foliar-applied urea increased the urea content and decreased the ammonia content and urease activity of soybean [Glycine max. (L.) Merr.] leaves fertilized with urea, it increased the leaf-tip necrosis observed after fertilization. We conclude that this necrosis resulted from accumulation of toxic amounts of urea rather than from formation of toxic amounts of ammonia. This conclusion was supported by our finding that the necrotic areas of soybean leaves treated with urea or with urea and phenylphosphorodiamidate contained much higher concentrations of urea than did the nonnecrotic areas. Images PMID:16594077

Krogmeier, Michael J.; McCarty, Gregory W.; Bremner, John M.

1989-01-01

30

40 CFR 721.9892 - Alkylated urea.  

Code of Federal Regulations, 2010 CFR

...2010-07-01 2010-07-01 false Alkylated urea. 721.9892 Section 721.9892 ...Chemical Substances § 721.9892 Alkylated urea. (a) Chemical substance and significant...substance identified generically as an alkylated urea (PMN P-93-1649) is subject to...

2010-07-01

31

Streamflow Routing  

NSDL National Science Digital Library

This module offers a thorough introduction to streamflow routing methods and applications in the river forecasting process. Through the use of rich illustrations, animations, and interactions, this module explains key routing concepts, flow characteristics, and tools with a primary focus on hydrologic routing methods. As a foundation topic for the Basic Hydrologic Science Course, this module may be taken on its own or used as a supporting topic to provide factual scientific information to students as they complete the case-based forecasting modules.

Comet

2006-03-17

32

Cycle Route  

NSDL National Science Digital Library

If you're an avid cyclist or just a neophyte, you'll find this rather unique app most useful. Cycle Route can assist those with a passion for cycling plan out their route based on topography, elevation, main roads, and a range of other variables. Visitors just need to enter their origin and destination and they will be all set. The app returns a range of routes that users can take advantage of and there's also a mobile version as well. This version is compatible with all operating systems.

2013-11-07

33

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

34

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

35

Urea biosensor for hemodialysis monitoring  

DOEpatents

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

Glass, R.S.

1999-01-12

36

Combustion noise  

NASA Technical Reports Server (NTRS)

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

Strahle, W. C.

1977-01-01

37

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. PMID:23616806

Lefranc, Julien; Minassi, Alberto

2013-01-01

38

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

39

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

40

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

41

Extraction of urea and ammonium ion  

NASA Technical Reports Server (NTRS)

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

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

1977-01-01

42

Route 66  

NSDL National Science Digital Library

Even though Route 66 hasn't formally existed in twenty years, it is part of America's love affair with cars, travel, and getting lost. This excellent travel itinerary created by the National Park Service's Heritage Education Services "aids the public to visit the historic places that recall those images and experiences that are reminders of our past and evidence of the influence of the automobile." The homepage features historic images of old motel facades and long-gone department stores along Route 66, mixed in with images of the Route today. To get a sense of the road's genealogy, visitors would do well to look through the illustrated "Essays". Here they can learn about the road's origins, its rise, decline, and renaissance over the past 85 years. Moving on, users can click on the "List of Sites" area to read about featured sites in each of the eight states that the road passes through. Finally, the "Learn More" area is a glorious cornucopia of related websites that tell the story of the places and people associated with the road, including Dell Rhea's Chicken Basket in Hinsdale, Illinois and the Seligman Historic District in Arizona.

43

40 CFR 721.9925 - Aminoethylethylene urea methacrylamide.  

Code of Federal Regulations, 2010 CFR

...2010-07-01 false Aminoethylethylene urea methacrylamide. 721.9925 Section...Substances § 721.9925 Aminoethylethylene urea methacrylamide. (a) Chemical substance...identified generically as an aminoethylethylene urea methacrylamide (PMN...

2010-07-01

44

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

45

Wavelength Routing Networks Wavelength Routing Networks -1  

E-print Network

Pag. 1 Wavelength Routing Networks Wavelength Routing Networks - 1 Optical Networks: from fiber transmission to photonic switching Wavelength-Routing Networks Fabio Neri and Marco Mellia TLC Networks Group.neri@polito.it ­ tel. 011 564 4076 marco.mellia@polito.it ­ tel. 011 564 4173 Wavelength Routing Networks - 2

Mellia, Marco

46

Intense green and red upconversion emission of Er3+,Yb3+ co-doped CaZrO3 obtained by a solution combustion reaction  

NASA Astrophysics Data System (ADS)

CaZrO3 phosphors co-doped with Er3+ and Yb3+ ions have been prepared by the urea combustion route. The formation of the orthorhombic phase of CaZrO3 was confirmed by powder x-ray diffraction. The absorption in the 280-1800 nm region and excitation spectrum corresponding to the emission at 545 nm for CaZrO3:Er3+/CaZrO3:Er3+,Yb3+ phosphors have been recorded. Upon excitation at 978 nm, the material displays strong energy transfer upconversion emission in the green and red spectral regions. The upconversion emission of the CaZrO3:Er3+,Yb3+ co-doped material shows an increased red-to-green ratio, indicating cross relaxation between Er3+ ions.

Singh, Vijay; Kumar Rai, Vineet; Haase, Markus

2012-09-01

47

Enzymatic characterization of a prokaryotic urea carboxylase.  

PubMed

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

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

2004-05-01

48

Enzymatic Characterization of a Prokaryotic Urea Carboxylase  

PubMed Central

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

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

2004-01-01

49

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

50

Pure and doped lanthanum manganites obtained by combustion method  

Microsoft Academic Search

Pure and strontium-doped lanthanum manganite nanopowders were obtained by solution combustion method using metal nitrates as oxidants and different organic compounds as fuel (?-alanine, glycine, urea and semioxamazide). Different molar ratios, fuel\\/oxidant, were chosen to study the effect of the fuel content on the phase formation and powder properties. The complex precursors isolated before ignition of the system, were characterized

D. Berger; C. Matei; F. Papa; D. Macovei; V. Fruth; J. P. Deloume

2007-01-01

51

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

Microsoft Academic Search

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

Siriwattana Banchorndhevakul

2002-01-01

52

Securing Internet Routing Securing Internet Routing  

E-print Network

Securing Internet Routing Jobtalk Securing Internet Routing Local $$ ISP Sharon Goldbergg Princeton Implement / Characterize Security vs Efficiency Implement / Tech transfer #12;Secure Routing on the Internet ll ti f A t S t (AS) The Internet (1) The Internet is a collection of Autonomous Systems (AS

Goldberg, Sharon

53

Biofuels Combustion  

NASA Astrophysics Data System (ADS)

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.

Westbrook, Charles K.

2013-04-01

54

Biofuels combustion.  

PubMed

This review describes major features of current research in renewable fuels derived from plants and from fatty acids. Recent and ongoing fundamental studies of biofuel molecular structure, oxidation reactions, and biofuel chemical properties are reviewed, in addition to combustion applications of biofuels in the major types of engines in which biofuels are used. Biofuels and their combustion are compared with combustion features of conventional petroleum-based fuels. Two main classes of biofuels are described, those consisting of small, primarily alcohol, fuels (particularly ethanol, n-butanol, and iso-pentanol) that are used primarily to replace or supplement gasoline and those derived from fatty acids and used primarily to replace or supplement conventional diesel fuels. Research efforts on so-called second- and third-generation biofuels are discussed briefly. PMID:23298249

Westbrook, Charles K

2013-01-01

55

Urea transporter knockout mice and their renal phenotypes.  

PubMed

Urea transporter gene knockout mice have been created for the study of the urine-concentrating mechanism. The major findings in studies of the renal phenotype of these mice are as follows: (1) Urea accumulation in the inner medullary interstitium is dependent on intrarenal urea recycling mediated by urea transporters; (2) urea transporters are essential for preventing urea-induced osmotic diuresis and thus for water conservation; (3) NaCl concentration in the inner medullary interstitium is not significantly affected by the absence of IMCD, descending limb of Henle and descending vasa recta urea transporters. Studies in urea transporter knockout mouse models have highlighted the essential role of urea for producing maximally concentrated urine. PMID:25298343

Fenton, Robert A; Yang, Baoxue

2014-01-01

56

Combustion & Health  

E-print Network

FFCOMBUSTION & HEALTH Winifred J. Hamilton, PhD, SM Clear Air Through Energy Efficiency (CATEE) Galveston, TX October 9?11, 2012 FFCOMBUSTION & HEALTH FFCOMBUSTION: THE THREAT ? Biggest threat to world ecosystems (and to human health...) ? Combustion of fossil fuels for ? Electricity ? Industrial processes ? Vehicle propulsion ? Cooking and heat ? Other ? Munitions ? Fireworks ? Light ? Cigarettes, hookahs? FFCOMBUSTION & HEALTH FFCOMBUSTION: THE THREAT ? SCALE (think health...

Hamilton, W.

2012-01-01

57

Turbulent combustion  

SciTech Connect

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

Talbot, L.; Cheng, R.K. [Lawrence Berkeley Laboratory, CA (United States)

1993-12-01

58

Pure and doped lanthanum cobaltites obtained by combustion method  

Microsoft Academic Search

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

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

2007-01-01

59

Combustion control  

Microsoft Academic Search

This patent describes an improved method of operating in a combustion process which is regulated by maintaining a preselected feed forward relationship of fuel input and air input. It comprises: establishing a fuel\\/air input peak relationship for the approximately stoichiometric condition which produces the maximum infrared radiation; selecting a desired operating fuel\\/air ratio based on a result of the fuel\\/air

Zabielski

1990-01-01

60

Advanced Combustion  

SciTech Connect

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

Holcomb, Gordon R. [NETL

2013-03-11

61

Urea: a comprehensive review of the clinical literature  

E-print Network

effect of salicylic acid and urea in human skin. Skinsalicylic acid alone CT Single 4-hour application on back skinsalicylic acid ointment, and paraffin-based moisturizers [17]. The beneficial effects of urea on ichthyotic skin

Pan, Michael; Heinecke, Gillian; Bernardo, Sebastian; Tsui, Cindy; Levitt, Jacob

2013-01-01

62

Aldehyde-containing urea-absorbing polysaccharides  

NASA Technical Reports Server (NTRS)

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

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

1977-01-01

63

Quantitative determination of urea concentrations in cell culture medium  

PubMed Central

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

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

2009-01-01

64

Phenol–urea–formaldehyde (PUF) co-condensed wood adhesives  

Microsoft Academic Search

The reaction of urea with methylolphenol under acidic conditions was investigated. The alternating copolymer of urea and phenol could be synthesized by the reaction of urea and 2,4,6-trimethylolphenol. The reactions of urea with polymethylolphenol mixtures also were investigated by changing the reaction conditions, such as the molar ratio and acidity. The co-condensates were analysed by carbon-13 nuclear magnetic resonance spectroscopy

Bunichiro Tomita; Chung-Yun Hse

1998-01-01

65

76 FR 15339 - Solid Urea From Russia and Ukraine  

Federal Register 2010, 2011, 2012, 2013

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

2011-03-21

66

76 FR 77015 - Solid Urea From Russia and Ukraine  

Federal Register 2010, 2011, 2012, 2013

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

2011-12-09

67

75 FR 74746 - Solid Urea From Russia and Ukraine  

Federal Register 2010, 2011, 2012, 2013

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

2010-12-01

68

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. ...

69

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

70

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

PubMed

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

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

2011-10-15

71

Routing in hybrid networks  

E-print Network

Hybrid networks are networks that have wired as well as wireless components. Several routing protocols exist for traditional wired networks and mobile ad-hoc networks. However, there are very few routing protocols designed for hybrid networks...

Gupta, Avinash

2012-06-07

72

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

73

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

74

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

75

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

76

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

77

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

78

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

79

Structural and electrochemical properties of LiCoO 2 prepared by combustion synthesis  

Microsoft Academic Search

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

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

2003-01-01

80

Neurological implications of urea cycle disorders  

PubMed Central

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

Summar, M.; Leonard, J. V.

2013-01-01

81

A longitudinal study of urea cycle disorders.  

PubMed

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

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

2014-01-01

82

Defining Dynamic Route Structure  

NASA Technical Reports Server (NTRS)

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

Zelinski, Shannon; Jastrzebski, Michael

2011-01-01

83

Safe Routing Reconfigurations with Route Redistribution  

E-print Network

mergers and acquisitions, or pragmatic reasons, e.g., a specific routing protocol not being supported domains. Splitting and merging networks, e.g., to accommodate mergers and acquisitions, are two radical

Xie, Geoffrey

84

Combustion chemistry  

SciTech Connect

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

Brown, N.J. [Lawrence Berkeley Laboratory, CA (United States)

1993-12-01

85

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

86

Combustion Fundamentals Research  

NASA Technical Reports Server (NTRS)

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

1983-01-01

87

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. PMID:8514890

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

1993-01-01

88

Contact Graph Routing  

NASA Technical Reports Server (NTRS)

Contact Graph Routing (CGR) is a dynamic routing system that computes routes through a time-varying topology of scheduled communication contacts in a network based on the DTN (Delay-Tolerant Networking) architecture. It is designed to enable dynamic selection of data transmission routes in a space network based on DTN. This dynamic responsiveness in route computation should be significantly more effective and less expensive than static routing, increasing total data return while at the same time reducing mission operations cost and risk. The basic strategy of CGR is to take advantage of the fact that, since flight mission communication operations are planned in detail, the communication routes between any pair of bundle agents in a population of nodes that have all been informed of one another's plans can be inferred from those plans rather than discovered via dialogue (which is impractical over long one-way-light-time space links). Messages that convey this planning information are used to construct contact graphs (time-varying models of network connectivity) from which CGR automatically computes efficient routes for bundles. Automatic route selection increases the flexibility and resilience of the space network, simplifying cross-support and reducing mission management costs. Note that there are no routing tables in Contact Graph Routing. The best route for a bundle destined for a given node may routinely be different from the best route for a different bundle destined for the same node, depending on bundle priority, bundle expiration time, and changes in the current lengths of transmission queues for neighboring nodes; routes must be computed individually for each bundle, from the Bundle Protocol agent's current network connectivity model for the bundle s destination node (the contact graph). Clearly this places a premium on optimizing the implementation of the route computation algorithm. The scalability of CGR to very large networks remains a research topic. The information carried by CGR contact plan messages is useful not only for dynamic route computation, but also for the implementation of rate control, congestion forecasting, transmission episode initiation and termination, timeout interval computation, and retransmission timer suspension and resumption.

Burleigh, Scott C.

2011-01-01

89

Urea hydrolysis and calcium carbonate reaction fronts  

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

90

1-Methyl-3-phenyl-thio-urea  

PubMed Central

The title compound, C8H10N2S, was prepared by reaction of methyl­amine solution, KOH and phenyl-iso­thio­cyanate in ethanol. It adopts a syn-Me and anti-Ph conformation relative to the C=S double bond. The dihedral angle between the N—C(=S)—N thio­urea and phenyl planes is 67.83?(6)°. In the crystal, the mol­ecules centrosymmetrical dimers by pairs of N(Ph)—H?S hydrogen bonds. The dimers are linked by N(Me)—H?S hydrogen bonds into layers parallel to (100). PMID:24860341

Su, Hou-xiang

2014-01-01

91

Functional Nanomaterials from Bis-urea Macrocycles  

NASA Astrophysics Data System (ADS)

Self-assembly of bis-urea macrocycles usually give tubular crystals with nano-sized channels that we use as molecular container. These molecular containers alter the reactivity, stability, and chemical behavior of the reactants entrapped within them. This dissertation is focused on bulk synthesis, material characterization and applications of a self-assembled tubular molecular container. This crystalline straw-like container is developed from cyclic bis-urea macrocycles containing two C-shaped phenylethynylene units and two urea groups. These macrocycles afford a large open channel with a diameter of ˜9 A and it can accommodate larger solid guests such as coumarin and its methylated derivatives, stilbenes, acenaphthylene and styrenes. We developed the method to introduce these solid guests into the channel from its solution. We characterized the tubular host as well as different host*guest complexes by solid-state techniques including PXRD, CP MAS 13C NMR, fluorescence and UV-vis spectroscopy. These guests usually undergo non selective photoreaction in solid-state with very low percent conversion and produce different photodimers and/or isomers. Within our molecular container, a number of guests showed photo-dimerization with amazing selectivity and enhanced conversion in the solid-state. We also performed molecular modeling studies to find out the reason behind this unprecedented selectivity. We found the orientation of the guest molecules inside the channel as well as the stability of the photoproducts within the confinement determines the outcome of the reactions. We also developed a 5,5'-bipyridine containing bis-urea macrocycle and formed its complexes with metals. These complexes have potential to further assemble through dative bonds, hydrogen bonding and aryl stacking interactions to afford metal organic framework (MOF). We found the Ag complex forms oligomers and polymers. In the polymer structure it forms infinite chains comprised of "box" like unit cell. In one unit cell, two silver atoms are 3.13 A apart suggesting a very interesting Ag-Ag bond interaction. We probed the Ag-Ag interaction by solid-state spectroscopic techniques as well as ESI-MS and Raman spectroscopy. The results indicate that there is indeed an interaction between the two silver atoms and their proximity is not merely a packing artifact.

Dawn, Sandipan

92

Difatty acyl urea from corn oil: synthesis and characterization.  

PubMed

In this study, difatty acyl urea has been successfully synthesized from corn oil using sodium ethoxide as a catalyst. Ethyl fatty ester and glycerol were produced as by-products. In this reaction, corn oil was refluxed with urea in ethanol. The highest conversion percentage (78%) was obtained when the process was carried out for 8 hours using urea to corn oil ratio of 5.6: 1.0 at 78 degrees C. Both difatty acyl urea and ethyl fatty ester have been characterized using elemental analysis, Fourier transform infrared (FTIR) spectroscopy and (1)H nuclear magnetic resonance (NMR) technique. PMID:20124758

Al-Mulla, Emad A Jaffar; Yunus, Wan Md Zin Wan; Ibrahim, Nor Azowa Bt; Rahman, Mohd Zaki A

2010-01-01

93

Osmolyte counteracts urea-induced denaturation of alpha-chymotrypsin.  

PubMed

The stability of proteins is reduced by urea, which is methylamine and nonprotecting osmolyte; eventually urea destabilizes the activity and function and alters the structure of proteins, whereas the stability of proteins is raised by the osmolytes, which are not interfering with the functional activity of proteins. The deleterious effect of urea on proteins has been counteracted by methylamines (osmolytes), such as trimethylamine N-oxide (TMAO), betaine, and sarcosine. To distinctly enunciate the comparison of the counteracting effects between these methylamines on urea-induced denaturation of alpha-chymotrypsin (CT), we measured the hydrodynamic diameter (d(H)) and the thermodynamic properties (T(m), DeltaH, DeltaG(U), and DeltaC(p)) with dynamic light scattering (DLS) and differential scanning calorimeter (DSC), respectively. The present investigation compares the compatibility and counteracting hypothesis by determining the effects of methylamines and urea, as individual components and in combination at a concentration ratio of 1:2 (methylamine:urea) as well as various urea concentrations (0.5-5 M) in the presence of 1 M methylamine. The experimental results revealed that the naturally occurring osmolytes TMAO, betaine, and sarcosine strongly counteracted the urea actions on alpha-chymotrypsin. The results also indicated that TMAO counteracting the urea effects on CT was much stronger than betaine or sarcosine. PMID:19354310

Venkatesu, Pannur; Lee, Ming-Jer; Lin, Ho-Mu

2009-04-16

94

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

95

21 CFR 862.1770 - Urea nitrogen test system.  

...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)...

2014-04-01

96

An investigation of urea decomposition and selective non-catalytic removal of nitric oxide with urea  

E-print Network

of urea-water solution decomposition, for gas temperatures between 550 and 650 K, the highest concentrations were for NH3 and HNCO. On the other hand, the concentrations of CO2 were highest for gas temperatures of about 500 - 550 K. For temperatures above...

Park, Yong Hun

2004-09-30

97

An excess electron bound to urea. III. The urea dimer as an electron trap Piotr Skurski  

E-print Network

binding to urea dimers in the gas-phase was studied at the coupled cluster level with single and double.e., the nonplanar Cs-symmetry ``syn'' conformation and the planar C2V structure also form stable anions of dipole Finally, we found that the syn conformation of isourea sup- ports a dipole-bound anionic state

Simons, Jack

98

Internet Routing Instability  

Microsoft Academic Search

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

Craig Labovitz; G. Robert Malan; Farnam Jahanian

1997-01-01

99

Bendable Routing Tool  

NASA Technical Reports Server (NTRS)

Tool extends routing bit into internal cavities or passages so burrs and similar defects removed. Bent so inserted through curving channels. Copper sheath gives stiffness to flexible shaft but can itself be bent. Several types of routing bits attached to shaft.

Mayer, Walter

1987-01-01

100

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

101

Streamflow Routing: International Edition  

NSDL National Science Digital Library

Streamflow routing provides a set of methods for describing and predicting the movement of water from one point to another along a river. Typically, this process involves predicting the shape of a hydrograph downstream from a particular location in a channel, reservoir, or lake. This first requires an understanding of the basic flow regimes and how water is stored and released within a channel. From there, information and calculations based on flow and channel bed characteristics are implemented in hydrologic routing methods, which are storage-based, and hydraulic routing methods, which utilize fully-dynamic equations. This module offers a thorough introduction to these routing concepts and processes through illustrations, animations and sample exercises, with a primary focus on hydrologic routing methods.

Comet

2010-10-19

102

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.

103

Persistent route oscillations in inter-domain routing  

Microsoft Academic Search

Hop-by-hop inter-domain routing protocols, such as border gateway protocol (BGP) and inter-domain routing protocol (IDRP), use independent route selection to realize domains' local policies. A domain chooses its routes based on path attributes present in a route. It is widely believed that these inter-domain routing protocols always converge. We show that there exist domain policies that cause BGP\\/IDRP to exhibit

Kannan Varadhan; Ramesh Govindan; Deborah Estrin

2000-01-01

104

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

105

Foliar applied urea improves freezing protection to avocado and peach  

Microsoft Academic Search

The effect of foliar applied urea on freeze hardiness was evaluated under orchard and laboratory conditions. Freezing injury and senescence of avocado (Persea americana Mill.) cv. ‘Hass’ leaves in the orchard was inversely correlated to N content. Three foliar applications of 2% low-biuret urea caused a 26% nitrogen enrichment of leaves. Consequently, leaf freezing hardiness was increased and senescence retarded.

S. Zilkah; Z. Wiesmann; I. Klein; I. David

1996-01-01

106

Managing Urea-Containing Fertilizers1 Larry G. Bundy2  

E-print Network

such as ammonium nitrate, ammonium sulfate, ammonium thiosulfate, aqua ammonia, calcium nitrate and others Nitrogen fertilizer use in Wisconsin as anhydrous ammonia, urea-ammonium nitrate solutions, and urea ranged. Utilization as ammonium nitrate plus ammonium sulfate ranged from about 24,000 tons of N in 1999 to 13

Balser, Teri C.

107

Ammonium assimilation in Proteus vulgaris, Bacillus pasteurii , and Sporosarcina ureae  

Microsoft Academic Search

No active uptake of ammonium was detected in Proteus vulgaris, Bacillus pasteurii, and Sporosarcina ureae, which indicates that these bacteria depend on the passive diffusion of ammonia across the cell membrane. In P. vulgaris the glutamine synthetase-glutamate synthase (GS-GOGAT) pathway and glutamate dehydrogenase (GDH) were present, and these enzymes exhibited high affinities for ammonium. In B. pasteurii and S. ureae,

Gerhard Miirsdorf; Heinrich Kaltwasser

1989-01-01

108

Aqueous urea solution destabilizes A 1622 oligomers D. K. Klimov*  

E-print Network

considered to be the primary pathogenic agents of the Alzheimer's disease (8). The amyloidogenic pathway, formation of soluble oligomeric intermediates, and gradual accumulation of protofibrils and fibril deposits in aqueous urea solution. High concentration of urea promotes the formation of -strand structures in A 16

Straub, John E.

109

Variability of urea concentration in camel milk in Kazakhstan  

E-print Network

Note Variability of urea concentration in camel milk in Kazakhstan Bernard FAYE 1*, Gaukhar-protein nitrogen in milk. The variability of its concentration was never reported in camel milk. The present communication aimed to give some reference values on urea content in camel milk and to explore some

Paris-Sud XI, Université de

110

Spectrophotometric determination of urea in sugar cane distilled spirits.  

PubMed

Urea is an important precursor in the formation of ethyl carbamate, a known carcinogen in alcoholic beverages. Ethyl carbamate has recently been detected at high concentrations in sugar cane distilled spirits, but little is known about the concentration of urea in these beverages. The objectives of this study were to validate methodology for the determination of urea in sugar cane distilled spirits, to determine the levels in 68 samples from different regions within the state of Minas Gerais, Brazil, and to examine the relationship between the concentrations of urea and ethyl carbamate. The method, based on the reaction of urea with 1-phenyl-1,2-propanodione-2-oxime and spectrophotometric quantification at 540 nm, provided linear response from 0.5 to 15.0 mg/L. No purification of the sample was required. The limits of detection and quantification were 0.1 and 0.5 mg/L, respectively. Urea was detected in 69% of the samples at levels varying from 0.50 to 5.10 mg/L. There was no significant difference on the levels of urea in samples from different regions of the state. No significant correlation between the levels of urea and ethyl carbamate was observed for the samples analyzed. PMID:18553892

Labanca, Renata A; Glória, M Beatriz A

2008-07-01

111

ON-FARM TREATMENT OF STRAWS AND STOVERS WITH UREA  

Microsoft Academic Search

ON-FARM TREATMENT OF STRAWS AND STOVER WITH UREA. The nutritional value of cereal crop residues to ruminants is constrained by low N and high fibre contents. These constraints can be alleviated by treatment with alkali, the most suitable of which, for smallholder use, is urea. However, it has not widely been used in Africa. Whilst in some areas, cost and

T. SMITH

112

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

Code of Federal Regulations, 2010 CFR

...2010-07-01 2010-07-01 false Urea, (hexahydro-6-methyl-2-oxopyrimidinyl...Specific Chemical Substances § 721.9920 Urea, (hexahydro-6-methyl-2-oxopyrimidinyl...reporting. (1) The chemical substance urea,...

2010-07-01

113

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

Federal Register 2010, 2011, 2012, 2013

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

2011-12-20

114

Regeneration of hemofiltrate by anodic oxidation of urea.  

PubMed

Urea can be oxidized electrochemically in a chloride solution to carbon dioxide, water, and nitrogen. The microkinetics of this hypochlorite-mediated urea oxidation are elucidated. Based on this kinetic information, the optimal conditions and construction principles for an electrochemical reactor are deduced. The construction of a cheap, disposable oxidation cell and necessary auxiliary equipment are described. In vitro data are reported for urea removal. A 36-L volume was used to simulate a 60-kg patient; 18 L was recirculated through a 0.12-m2 oxidation cell. Within 3 h, 35 g urea could be removed from the system. The technical and economic possibilities as well as safety requirements for hemofiltrate regeneration to a reinfusable substitution solution by anodic urea oxidation are discussed critically. Although the process does not appear to be economically practical for discontinuous hemofiltration, it might be desirable for continuous (24 h/day) treatment. PMID:6307234

Köster, K; Wendt, H; Gallus, J; Krisam, G; Lehmann, H D

1983-05-01

115

Structure and permeation mechanism of a mammalian urea transporter  

SciTech Connect

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

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

2012-09-17

116

Residual renal function and post dialysis urea rebound.  

PubMed

Kt/v is used to estimate haemodialysis prescription and treatment adequacy and usually does not include evaluation of urea rebound. In addition urea clearance provided by the presence of residual renal function (RRF) is additive to dialytic urea clearance. Rebound is a phenomenon involving other molecules such as creatinine and phosphorus. The aim of this study was to investigate the role of RRF on post dialysis urea, creatinine and phosphorus rebounds. We investigated 7 patients with RRF (group 1) and 7 uraemic anuric patients (group 2). Urea rebound was lower in group 1 than group 2: 9.5 +/- 4% vs 18 +/- 7% (p = 0.04). Creatinine rebound and phosphorus rebound were similar in both groups 15.2 +/- 9% group 1 vs 14.6 +/- 5% group 2 (p = NS) and 16.7 +/- 7% group 1 vs 20 +/- 7% group 2 (p = NS) respectively. Our data suggest Kt/v calculated without considering rebound overestimates haemodialysis efficacy. PMID:10531872

Carofei, O; Taratufolo, A; Atti, S; Fringuello, F; Alaimo, M

1999-01-01

117

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

PubMed

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

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

2014-09-30

118

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

119

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

120

The combustion process  

NASA Technical Reports Server (NTRS)

The effect of thermodynamic, chemical, and physical properties on the combustion of materials is discussed. The mechanisms which produce and support combustion of various materials are examined. The effects of free radical reactions, convection and gravitational effects on combustion rates, and changes in flame propagation due to size and shape of surfaces are described.

Downs, W. R.

1971-01-01

121

BOOK REVIEW: Turbulent Combustion  

Microsoft Academic Search

The book Turbulent Combustion by Norbert Peters is a concise monograph on single-phase gaseous low Mach number turbulent combustion. It is compiled from the author's review papers on this topic plus some additional material. Norbert Peters characterizes turbulent combustion both by the way fuel and air are mixed and by the ratio of turbulent and chemical time scales. This approach

Norbert Peters

2001-01-01

122

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

123

On Routing and \\  

Microsoft Academic Search

An inherent capability of packet-switched networks is the speed at which they can be reconfigured; various dynamic or adaptive routing techniques have been conceived to exploit this capability. In this study, existing techniques are described and an \\

H. Rudin

1976-01-01

124

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

125

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

126

Trehalose protects urea-induced unfolding of ?-chymotrypsin.  

PubMed

Trehalose, a naturally occurring osmolyte, appears to be one of the most effective protectants for enzymes under various stress conditions while urea, a classical denaturant, destabilizes the activity, function, and alters the native structure of proteins. Herein, we have characterized the counteracting effects of trehalose on the deleterious effect of urea on ?-chymotrypsin (CT) through the calorimetric data (transition temperature (T(m)), enthalpy change (?H), heat capacity change (?C(p)) and Gibbs free energy of unfolding (?G(u)) by using differential scanning calorimeter (DSC) and circular dichroism (CD) techniques, respectively, at a 1:2 ratio of trehalose and urea, as well as various urea concentration (up to 6 M) in the presence of 1 M trehalose. Our parallel experimental results explicitly elucidate that trehalose strongly offset the deleterious actions of urea on CT at 1:2 molar ratio of trehalose and urea, however, trehalose (1 M) some how failed to counteract the perturbation effects of urea (3-6 M) on CT. PMID:20691724

Kumar, Awanish; Attri, Pankaj; Venkatesu, Pannuru

2010-11-01

127

Modeling Routing Overhead Generated by Wireless Proactive Routing Protocols  

E-print Network

In this paper, we present a detailed framework consisting of modeling of routing overhead generated by three widely used proactive routing protocols; Destination-Sequenced Distance Vector (DSDV), Fish-eye State Routing (FSR) and Optimized Link State Routing (OLSR). The questions like, how these protocols differ from each other on the basis of implementing different routing strategies, how neighbor estimation errors affect broadcast of route requests, how reduction of broadcast overhead achieves bandwidth, how to cope with the problem of mobility and density, etc, are attempted to respond. In all of the above mentioned situations, routing overhead and delay generated by the chosen protocols can exactly be calculated from our modeled equations. Finally, we analyze the performance of selected routing protocols using our proposed framework in NS-2 by considering different performance parameters; Route REQuest (RREQ) packet generation, End-to-End Delay (E2ED) and Normalized Routing Load (NRL) with respect to varyi...

Javaid, Nadeem; Javaid, Akmal; Malik, Shahzad A

2011-01-01

128

Modeling Routing Overhead Generated by Wireless Reactive Routing Protocols  

E-print Network

In this paper, we have modeled the routing over- head generated by three reactive routing protocols; Ad-hoc On-demand Distance Vector (AODV), Dynamic Source Routing (DSR) and DYnamic MANET On-deman (DYMO). Routing performed by reactive protocols consists of two phases; route discovery and route maintenance. Total cost paid by a protocol for efficient routing is sum of the cost paid in the form of energy consumed and time spent. These protocols majorly focus on the optimization performed by expanding ring search algorithm to control the flooding generated by the mechanism of blind flooding. So, we have modeled the energy consumed and time spent per packet both for route discovery and route maintenance. The proposed framework is evaluated in NS-2 to compare performance of the chosen routing protocols.

Javaid, Nadeem; Javaid, Akmal; Malik, Shahzad A

2011-01-01

129

Urea encapsulation in modified starch matrix for nutrients retention  

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

130

Routing Slips from the Computer  

ERIC Educational Resources Information Center

To facilitate the routing of periodicals, a computerized system of printing and updating routing lists was designed to replace a manual one. A computer program generates a data base of staff routing choices and prints out routing slips for each periodical. (Author/NH)

Blair, Joan

1972-01-01

131

14 CFR 221.41 - Routing.  

Code of Federal Regulations, 2010 CFR

... 4 2010-01-01 2010-01-01 false Routing. 221.41 Section 221.41 Aeronautics and...REGULATIONS TARIFFS Contents of Tariff § 221.41 Routing. (a) Required routing. The route or routes over which each...

2010-01-01

132

Formation of urea and guanidine by irradiation of ammonium cyanide.  

NASA Technical Reports Server (NTRS)

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

Lohrmann, R.

1972-01-01

133

Urea photosynthesis inside polyelectrolyte capsules: effect of confined media.  

PubMed

The influence of the restricted volume of poly(styrene sulfonate)/poly(allylamine hydrochloride) capsules of different size (2.2, 4.2, and 8.1 microm) on the TiO2-assisted photosynthesis of urea from inorganic precursors (CO2 and NO(3-)) in aqueous solution was demonstrated. Poly(vinyl alcohol) was employed as electron donor to facilitate the photosynthetic process. Decreasing the size of the confined microvolume of polyelectrolyte capsules accelerates the NO(3-) photoreduction, which is a limiting stage of the urea photosynthesis and, correspondingly, increases the efficiency of urea production. The highest yield of urea photosynthesis (37%) was achieved for Cu-modified TiO2 nanoparticles encapsulated inside 2.2 microm poly(styrene sulfonate)/poly(allylamine hydrochloride) capsules. PMID:15924493

Shchukin, Dmitry G; Möhwald, Helmuth

2005-06-01

134

IRIS Toxicological Review of Urea (Interagency Science Discussion Draft)  

EPA Science Inventory

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

135

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

NASA Technical Reports Server (NTRS)

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

Geiger, P. J.

1969-01-01

136

IRIS TOXICOLOGICAL REVIEW OF UREA (EXTERNAL REVIEW DRAFT)  

EPA Science Inventory

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

137

67 FR 78713 - Urea: Revocation of Tolerance Exemptions  

Federal Register 2010, 2011, 2012, 2013

...This exemption is for its use as an adjuvant/intensifer for herbicides. 3. Another exemption from the requirement...d) the entry for urea ``use as an adjuvant/intensifier for herbicides.'' iii. Removing from the table...

2002-12-26

138

Crystal Structure of Urea Carboxylase Provides Insights into the Carboxyltransfer Reaction*S  

E-print Network

in many bacteria, algae, and fungi and catalyzes the conversion of urea to allophanate, an essential step, fungi, algae, and bacteria possess an enzymatic activity that converts urea to ammonium, enabling them to uti- lize urea as a nitrogen source (1­3). In agriculture, urea is widely used as a fertilizer

Tong, Liang

139

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

140

UREA LEVELS AND SUPPLEMENTAL ENERGY SOURCES IN SUGARCANE DIETS I  

Microsoft Academic Search

Two experiments, each involving a digestion-N balance trial and a feedlot trial, determined the replacement value of urea-corn meal (UC) for cottonseed meal (CSM) and the value of mo- lasses in sugarcane diets. Steers fed 70% sugarcane-30% concentrate diets with O, 28 or 56% of the dietary N as urea had a slight reduction (P<.28) in dry matter (DM) intake

F. M. Pate; P. M. Fairhurst; J. T. K. Munthali

141

Influence of herbicides on transformations of urea nitrogen in soil  

Microsoft Academic Search

The influence of 28 formulated herbicides on transformations of urea nitrogen in soil was studied by determining the effects of 5 and 50 mg active ingredient kg soil of each herbicide on the amounts of urea hydrolyzed and the amounts of nitrite and nitrate produced when samples of two coarse?textured soils and two fine?textured soils were incubated aerobically at 20°C

D. A. Martens; J. M. Bremner

1993-01-01

142

Structural changes in urea-formaldehyde resins during storage  

Microsoft Academic Search

13  C NMR spectroscopy. The three-step synthesis produces the resin consisting of two parts: the polymeric part from condensation\\u000a of formaldehyde with first amount of urea, and monomeric part formed after addition of second part of urea. Some differences\\u000a in structure depending on details of synthesis are of temporary character and level mainly in transhydroxymethylation from\\u000a polymeric to monomeric part of

P. Christjanson; K. Siimer; T. Pehk; I. Lasn

2002-01-01

143

Sensitivity to Urea Fertilization in Three Amphibian Species  

Microsoft Academic Search

Forest fertilization with granular urea is a well-established management practice in many forested regions of the world. We\\u000a hypothesize that chemical forest fertilizers may be affecting forest-dwelling wildlife. In the laboratory, we studied the\\u000a effects of fertilization doses of granular urea on three species of forest-dwelling amphibians (Plethodon vehiculum, Rhyacotriton variegatus, and Taricha granulosa). In avoidance experiments, the three species

A. Marco; D. Cash; L. K. Belden; A. R. Blaustein

2001-01-01

144

Urea secretion by the straight segment of the proximal tubule.  

PubMed Central

Studies utilizing in vitro microperfusion were designed to examine whether urea is actively or passively transported across superficial and juxtamedullary straight segments of rabbit proximal tubules. With perfusate and bath solutions containing 1 mM urea and electrolytes similar to normal plasma, the efflux (lumen-to-bath) isotopic permeability (X 10(-5) cm s-1) of superficial segments was 1.37 +/- 0.16 and of juxtamedullary segments was 2.14 +/- 0.20. In the same tubules, the influx (bath-to-lumen) isotopic permeability was 3.70 +/- 0.35 in superficial segments and 4.75 +/- 0.37 in juxtamedullary segments. Despite net water movement in the opposite direction (0.5 nl mm-1 min-1), the influx rate was significantly higher than the efflux rate of urea in both groups. With a low perfusion rate (2 nl/min) and equivalent specific activities of [14C]urea in bath and perfusate, the collected-to-perfused ratio of [14C]urea, corrected for volume marker change, was 1.07 +/- 0.01 in superficial and 1.09 +/- 0.01 in juxtamedullary nephrons, thus indicating net secretion in both segments. In separate studies urea influx was inhibited by hypothermia (decrease from 37 degrees to 28 degrees C), by phloretin (0.1 mM in bath), by cyanide (1 mM), but not by probenecid (0.2 mM). In each case the inhibition was highly significant and reversible. These data suggest that urea is actively secreted by the straight segments of both the superficial and juxtamedullary proximal tubules. These segments may, therefore, contribute significantly to the high urea concentration found at the bend of Henle's loop by micropuncture. PMID:956389

Kawamura, S; Kokko, J P

1976-01-01

145

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

146

Urea and ureolytic activity in lakes of different trophic status.  

PubMed

Urea and uraease (U-ase) activity were determined in water samples taken from the surface layers of 17 lakes of different trophic status. Urea concentrations were inversely correlated with the trophic status of the studied lakes and varied from below the detection limit to 25 micromol l(-1). Maximal potential ureolytic activity (V(max)) ranged from 0.2 to 7.0 micromol l(-1) h(-1). The highest urea concentrations and the lowest U-ase activities were recorded in the spring, whereas the lowest urea concentrations and the highest rates of urea hydrolysis were observed late in summer, during heavy phytoplankton blooms. Since in the majority of the Great Mazurian Lakes microplankton growth was limited by nitrogen supply, urea was an important N source for both auto- and heterotrophic planktonic microorganisms throughout the growth period. U-ase activity was mainly related to the seston. Only up to 25% of total activity could be attributed to free enzymes dissolved in lake water. In epilimnetic water samples the bulk of the ureolytic activity originated from seston-attached bacteria. However, a positive, statistically significant correlation between ureolytic activity and chlorophyll a (Chl(a)) concentrations suggests that phytoplankton may also be responsible for at least a some of the observed ureolytic activity in the highly eutrophic Great Mazurian Lakes. PMID:17338274

Siuda, Waldemar; Chróst, Ryszard J

2006-01-01

147

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

2013-03-15

148

The Triangular Trade Route  

NSDL National Science Digital Library

What is the Triangular Trade Route? After completeing this project, you should be able to explain the Triangular Trade Route in detail. These details should include the reason for trade, the countries involved, and the main goods that were traded. Getting Started: Each number will give you instructions. Follow the instructions, answering the questions on a loose leaf sheet of paper. Your answers will be collected. 1. What do you already know about trade? Answer this question in your own words. There is no right or wrong answer. 2. Have you ever traded ...

Caldwell, Ms.

2009-07-07

149

Tripropellant combustion process  

NASA Technical Reports Server (NTRS)

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

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

1988-01-01

150

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

Microsoft Academic Search

After conducting a preliminary survey, a feeding trial was carried out to determine the effect of urea–molasses–multinutrient block (UMMB) and urea-treated rice straw (UTRS) as a feed supplement on the productivity of dairy cows. Sixty Holstein–Friesian crossbred cows on 11 smallholder farms were divided equally into control, UMMB and UTRS supplementation groups. Milk yield and feed intake were recorded daily.

Doan Duc Vu; Le Xuan Cuong; Chung Anh Dung; Pham Ho Hai

1999-01-01

151

Delayed internet routing convergence  

Microsoft Academic Search

This paper examines the latency in Internet path failure, failover and repair due to the convergence properties of interdomain routing. Unlike switches in the public telephony network which exhibit failover on the order of milliseconds, our experimental measurements show that inter-domain routers in the packet switched Internet may take tens of minutes to reach a consistent view of the network

Craig Labovitz; Abha Ahuja; Abhijit Bose; Farnam Jahanian

2000-01-01

152

Recent Problems Alternative Routes  

E-print Network

#12; History Recent Problems Alternative Routes #12; Built in 1936 Length: 8.4 miles Made up Completion date slotted for late 2013 #12; One mile stretch linking Interstate 80 to Bay Bridge Needed Span 1.2 miles Five Lanes, 10 foot shoulders to keep traffic moving #12; Will connect Interstate 80

Nagurney, Anna

153

Route guidance information for elderly passengers: route naming methods  

E-print Network

-and-color identification. Systems in Monterey, California; Tampa, Florida; and Phoenix, Arizona also designed or modified their route guidance information with advice and suggestions from their passengers. Color Of the 20 "small" bus systetns that used color... prepared. The first was left unchanged except for the modifications already mentioned. The second was prepared with modified route names which added "N", "S", "E", or "W" to the street names which identified the routes: "Route 30 ? Burton", for example...

Higgins, Laura Lynne

2012-06-07

154

Route: A Name Based Routing Scheme for Information Centric Networks  

E-print Network

Route: A Name Based Routing Scheme for Information Centric Networks Reaz Ahmed, Md. Faizul Bari of Computer Science, University of Waterloo {mfbari | sr2chowdhury | m6rabban | r5ahmed | rboutaba, (iii) routing cannot depend on topological prefix binding as content retrieval should be location

Boutaba, Raouf

155

Routing with Bounded Buffers and HotPotato Routing  

E-print Network

auf der Heide and Christian Scheideler Department of Mathematics and Computer Science and Heinz for storing routing tables influences the runtime. For hot­potato routing, even without space restrictions would involve the packets to be stored in electronic media. In this paper we present on­line routing

Paderborn, Universität

156

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

157

Segmented poly(esterurethane urea)s from novel urea-diol chain extenders: synthesis, characterization and in vitro biological properties.  

PubMed

This work describes the preparation, physicochemical characterization, mechanical properties and in vitro biological properties of two bioresorbable aliphatic segmented poly(esterurethane urea)s (SPEUU) based on poly(epsilon-caprolactone) diol (PCL diol), 1,6-hexamethylene diisocyanate and two novel urea-diol chain extenders. To strengthen the interactions through hydrogen bonding in the hard segments of SPEUU, novel chain extenders containing urea groups were synthesized and used in the SPEUU formulation. The different chemical structures of the chain extenders modulated the phase separation of soft and hard segments, as demonstrated by the thermal behavior. The hard segment association was enhanced using a diurea-diol chain extender. The biological interactions between the obtained materials and blood were studied by in vitro methods. Research on the protein adsorption, platelet adhesion and thrombus formation is presented. Studies of protein adsorption onto polymeric surfaces showed that SPEUU adsorbed more albumin than fibrinogen. Studies on platelet adhesion and thrombus formation of SPEUU-coated coverslips indicated the antithrombogenic behavior of these surfaces. The synthesized SPEUU revealed no signs of cytotoxicity to Chinese hamster ovary cells, showing satisfactory cytocompatibility. PMID:18359673

Caracciolo, P C; de Queiroz, A A A; Higa, O Z; Buffa, F; Abraham, G A

2008-07-01

158

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

NASA Astrophysics Data System (ADS)

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

Tamrakar, Raunak Kumar; Bisen, D. P.

2013-06-01

159

Solution combustion synthesis and optimization of phosphors for plasma display panels  

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

160

Thermoluminescent properties of Mn-doped YAP synthesized by the solution combustion method  

NASA Astrophysics Data System (ADS)

The work describes results of Mn-doped YAlO3 (YAP) nanocrystalline materials synthesized by the solution combustion method using urea as a fuel. The materials were characterized by X-ray powder diffraction, scanning electron microscopy and luminescence techniques. The combustion synthesis method with codoping with Hf4+ ions allows to obtain highly efficient YAP:Mn2+ phosphor with negligible emission from Mn4+ ions that can be applicable for thermoluminescent dosimetry of ionizing radiation. Namely, the phosphor has a single dominating thermal glow peak at about 200 °C with the green emission near 530 nm related to Mn2+(Y) ions.

Zhydachevskii, Ya.; Kami?ska, I.; Fronc, K.; Reszka, A.; Paszkowicz, W.; Warchol, S.; Berkowski, M.; Elbaum, D.; Suchocki, A.

2014-11-01

161

ASRM combustion instability studies  

NASA Technical Reports Server (NTRS)

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

Strand, L. D.

1992-01-01

162

Fifteenth combustion research conference  

SciTech Connect

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

NONE

1993-06-01

163

Synthesis of red-emitting, small particle size luminescent oxides using an optimized combustion process  

Microsoft Academic Search

A novel ceramic synthesis technique, combustion synthesis, was explored to produce red-emitting Cr{sup 3+}-doped YâAlâOââ and Eu{sup 3+}-doped YâOâ phosphors with improved physical and luminescent properties. This technique involves the reaction of metal nitrates (oxidizers) and an organic fuel (urea, carbohydrazide, glycine) at 500 C. Resulting powders are well-crystallized, with a large surface area and small particle size. The spectral

Lauren E. Shea; Joanna McKittrick; Olivia A. Lopez; Esther Sluzky

1996-01-01

164

Nanocrystalline Cr 2O 3 and amorphous CrO 3 produced by solution combustion synthesis  

Microsoft Academic Search

The synthesis of chromium oxides by solution combustion synthesis was investigated. Ammonium dichromate, glycine, urea and ammonium nitrate dissolved in aqueous solution were used as the precursors of the oxides. The effect of different reaction parameters, such as fuel richness, stoichiometry and fuel leanness was evaluated; such parameters were modified by changing the reagents and the fuel\\/oxidant ratio. Amorphous CrO3

M. D. Lima; R. Bonadimann; M. J. de Andrade; J. C. Toniolo; C. P. Bergmann

2006-01-01

165

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

Microsoft Academic Search

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

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

2000-01-01

166

A combustion synthesis method to obtain alternative cermet materials for SOFC anodes  

Microsoft Academic Search

Homogeneous mixtures of nanocrystalline powders of Ni–YSZ, (Ni,Co)–YSZ, (Ni,Fe)–YSZ, and (Ni,Cu)–YSZ were obtained by combustion synthesis from mixtures of molten nitrates and urea. Electrolyte\\/anode bilayers were then prepared by pressing a cermet layer onto a previously pressed yttria-stabilised zirconia (YSZ) electrolyte layer, at room temperatures, and then co-firing; this yields a porous cermet anode, and a dense YSZ layer with

A Ringuedé; J. A Labrincha; J. R Frade

2001-01-01

167

Routing problem with service choices  

E-print Network

This thesis finds solutions to the routing problem with service choices which is formulated as a capacitated minimum cost flow circulation problem with GUB constraints. The routing problem with service choices is solved ...

Lee, Boon Chai

1986-01-01

168

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

169

Masked Proportional Routing  

NASA Technical Reports Server (NTRS)

Masked proportional routing is an improved procedure for choosing links between adjacent nodes of a network for the purpose of transporting an entity from a source node ("A") to a destination node ("B"). The entity could be, for example, a physical object to be shipped, in which case the nodes would represent waypoints and the links would represent roads or other paths between waypoints. For another example, the entity could be a message or packet of data to be transmitted from A to B, in which case the nodes could be computer-controlled switching stations and the links could be communication channels between the stations. In yet another example, an entity could represent a workpiece while links and nodes could represent, respectively, manufacturing processes and stages in the progress of the workpiece towards a finished product. More generally, the nodes could represent states of an entity and the links could represent allowed transitions of the entity. The purpose of masked proportional routing and of related prior routing procedures is to schedule transitions of entities from their initial states ("A") to their final states ("B") in such a manner as to minimize a cost or to attain some other measure of optimality or efficiency. Masked proportional routing follows a distributed (in the sense of decentralized) approach to probabilistically or deterministically choosing the links. It was developed to satisfy a need for a routing procedure that 1. Does not always choose the same link(s), even for two instances characterized by identical estimated values of associated cost functions; 2. Enables a graceful transition from one set of links to another set of links as the circumstances of operation of the network change over time; 3. Is preferably amenable to separate optimization of different portions of the network; 4. Is preferably usable in a network in which some of the routing decisions are made by one or more other procedure(s); 5. Preferably does not cause an entity to visit the same node twice; and 6. Preferably can be modified so that separate entities moving from A to B do not arrive out of order.

Wolpert, David

2004-01-01

170

Routing of printed circuit boards  

Microsoft Academic Search

A SOFTWARE PROGRAM FOR THE ROUTING OF PRINTED CIRCUIT BOARDS IS DISCUSSED IN THIS PAPER. THIS PROGRAM IS PART OF A SYSTEM WHICH INCLUDES READING DATA FROM THE ENGINEER'S SCHEMATIC DIAGRAM, PLACING THE COMPONENTS ON THE BOARD, AND ROUTING THE CONNECTIONS. THE LAYOUT IS THEN WORKED UPON ON A GRAPHIC DISPLAY TO IMPROVE AND COMPLETE THE ROUTING, WHICH IS THEN

S. Aranoff; Y. Abulaffio

1981-01-01

171

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

172

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

173

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

174

The regulation of urea-biosynthesis enzymes in vertebrates  

PubMed Central

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

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

1965-01-01

175

Predialysis urea concentration is sufficient to characterize hemodialysis adequacy.  

PubMed

Mathematical description of urea kinetics for a week showed that, under steady state conditions (i.e., total removal equals total synthesis), any predialysis urea concentration is expressed as a linear function of specific urea generation (G/V) and of dialysis schedule timing and sessional Kt/V (product of clearance, K, and session time, t, divided by the urea distribution volume, V). It also predicts that TACurea is proportional to the predialysis concentrations. The ratio between the two depends linearly on delivered weekly dialysis dose ([wDD] = T(G/V)/TACurea, with T the number of hours in 1 week). These hypotheses have been tested by retrospectively analyzing urea kinetc modelling data that include all predialysis and post dialysis concentrations of 163 patient-weeks. All patients were anuric, and dialysis frequency was thrice weekly. Accuracy is assessed with regression analysis between database numbers and computed values. The theoretical ratio between midweek concentration and TACurea (1.43) is close to the computed ratio (1.46, r2 = 0.909). TACurea (slope = 1.002, r2 = 0.997), specific generation rate G/V as a precursor to PCRn (slope = 1.007, r2 = 0.985), and wDD (slope = 1.002, r2 = 0.909) are all accurately computed from predialysis concentrations. To aid in the determination of the ratio for the different predialysis, concentrations using wDD a nomogram is included. PMID:9804519

De Wachter, D S; Brems, S; Vanholder, R; Verdonck, P R; Hombrouckx, R O

1998-01-01

176

Sensitivity to urea fertilization in three amphibian species.  

PubMed

Forest fertilization with granular urea is a well-established management practice in many forested regions of the world. We hypothesize that chemical forest fertilizers may be affecting forest-dwelling wildlife. In the laboratory, we studied the effects of fertilization doses of granular urea on three species of forest-dwelling amphibians (Plethodon vehiculum, Rhyacotriton variegatus, and Taricha granulosa). In avoidance experiments, the three species avoided a substrate treated with a dose of 225 kg N/ha urea. In toxicity experiments, we exposed amphibians to urea at doses of 225 kg N/ha and 450 kg N/ha for 4 days. The observed effects increased with time and dose, and there were significant differences in sensitivity among the species. Both treatment levels had an acute effect on survival of P. vehiculum and R. variegatus. At 24 h, mortality at the highest dose was 67% for P. vehiculum, and 47% for R. variegatus. In contrast, there was no mortality for T. granulosa at these concentrations. We suggest that environmental levels of urea could be affecting behavior and survival of some amphibians species in fertilized forests. PMID:11443373

Marco, A; Cash, D; Belden, L K; Blaustein, A R

2001-04-01

177

Application of Individualized Bayesian Urea Kinetic Modeling to pediatric hemodialysis.  

PubMed

Incorporating urea rebound using equilibrated urea concentration (Ceq) after hemodialysis (HD) is essential for accurate assessment of HD efficiency. It is impractical to measure Ceq in clinical settings, and there are no recommended methodologies to predict Ceq in children. The objective of this work is to assess the ability of an Individualized Bayesian Urea Kinetic Model (IBKM) for predicting Ceq in children receiving HD. Developed based on adult HD data, the IBKM is a two-pool urea kinetic model that calculates Bayesian estimates of individual Ceq. Blood urea nitrogen (BUN) samples from 30 HD sessions in 13 children (age 12-18 years) were taken at pre-HD, immediately post-HD, and 60 minutes post-HD (Ceq). The IBKM and estimated population parameters from adult data were fitted to the observed data from children to predict individual Ceq using NONMEM VI software in comparison with observed Ceq (9.5 +/- 3.8 mmol/L), the average individual predicted Ceq was 9.4 +/- 3.8 mmol/L, with absolute individual prediction error of 6.2% +/- 4.4%. For a given dialysis goal and desired dialysis duration, the required blood flow rate and dialyzer size are predicted by IBKM and confirmed by the analysis data. This study suggests that the IBKM can be used in a pediatric HD setting and accurately predict Ceq in children using only pre-HD and immediately post-HD BUN. PMID:20168209

Marsenic, Olivera; Zhang, Liping; Zuppa, Athena; Barrett, Jeffrey S; Pfister, Marc

2010-01-01

178

14C-urea breath test in C pylori gastritis.  

PubMed Central

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

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

1989-01-01

179

49 CFR 356.9 - Elimination of routing restrictions-regular route carriers.  

Code of Federal Regulations, 2010 CFR

... 2010-10-01 false Elimination of routing restrictions-regular route carriers. ...CARRIER SAFETY REGULATIONS MOTOR CARRIER ROUTING REGULATIONS § 356.9 Elimination of routing restrictions—regular route carriers....

2010-10-01

180

Influences of dietary sucrose and urea on transfer of endogenous urea to the rumen of sheep and numbers of epithelial bacteria.  

PubMed

1. The rates of transfer of plasma urea to the rumen of six sheep given brome grass (Bromus inermis) pellets alone or with supplements of sucrose or urea were determined using [14C] urea and 14C-labelled sodium bicarbonate infusions during three periods. 2. The sheep were slaughtered after the third period and samples of rumen epithelium were taken for assessment of numbers of adherent bacteria. 3. Maximum transfer (0.31 g nitrogen/h) of urea ot the rumen was observed for sheep given supplements of 150 g sucrose/d plus 20 g urea/d. Maximum clearance of plasma urea to the rumen (rate of urea transfer to the rumen per unit plasma urea concentration, 5.8 1/h) was observed for sheep given 300 g sucrose/d. 4. Urea clearance to the rumen was negatively related to rumen ammonia concentration; the slope of the relationship was increased with each addition of sucrose to the diet. 5. Numbers of facultative bacteria adherent to the rumen epithelium were increased by urea and sucrose supplements. 6. The results are discussed in relation to a hypothesis which relates the ureolytic capability of the bacteria adherent to the rumen epithelium to the control of the rate of transfer of urea into the rumen. PMID:7317347

Kennedy, P M; Clarke, R T; Milligan, L P

1981-11-01

181

Transportation Routing Analysis Geographic Information System (TRAGIS)  

E-print Network

Transportation Routing Analysis Geographic Information System (TRAGIS) Model and Network Databases The Transportation Routing Analysis Geographic Information System (TRAGIS) model is a geographic information system tool for modeling transportation routing. TRAGIS offers numerous options for route calculation

182

Competitive Performance Assessment of Dynamic Vehicle Routing  

E-print Network

Competitive Performance Assessment of Dynamic Vehicle Routing Technologies Using Sequential to implement more sophisticated Dynamic Vehicle Routingsophisticated Dynamic Vehicle Routing Technologies (DVR decision systems #12;Dynamic Vehicle Routing Technologies have toDynamic Vehicle Routing Technologies have

Marcotte, Patrice

183

Role for urea in nitrification by polar marine Archaea  

PubMed Central

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

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

2012-01-01

184

Role for urea in nitrification by polar marine Archaea.  

PubMed

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

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

2012-10-30

185

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

186

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

187

Gas turbine combustion instability  

SciTech Connect

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

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

1996-09-01

188

Large amplitude vibrations of Urea in gas phase  

NASA Astrophysics Data System (ADS)

Large amplitude motions of isolated Urea are analyzed using CCSD(T) calculations. Urea shows two conformers of C s and C 2 symmetries that interconvert through the NH 2 torsion and the NH 2 inversion motions. Anharmonic frequencies are computed using second order perturbation theory and an ab initio force field. The potential energy surface shows 16 minima. Nine stationary points are determined. Five reduced Hamiltonians are used for the vibrational energy determination, concluding that at least a variational treatment based on a 4D model is required for the FIR spectrum simulation. The inversion barrier produces a large splitting of the vibrational ground state.

Inostroza, N.; Senent, M. L.

2012-02-01

189

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

PubMed Central

The title compound, [Co(CH3COO)2(CH4N2S)2], is isotypic with the corresponding ZnII complex. The metal atom is in a distorted tetra­hedral coordination environment with the two S atoms from two thio­urea ligands and two O atoms from two acetate anions as the coordinating atoms. All H atoms of the thio­urea ligands are involved in N—H?O and N—H?S hydrogen bonds, leading to a three-dimensional network. PMID:24764944

Lutz, Martin

2014-01-01

190

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. PMID:22347105

Ashurov, Jamshid; Ibragimov, Bakhtiyar; Talipov, Samat

2012-01-01

191

The Action of Certain Acid Reagents on the Substituted Ureas  

E-print Network

and METHYL PHENYL UREA CHLORIDE with PYRIDINE. Ph Ph-N -Me Ph-N~Et >-H + >>-0 4 C.H.N — > >C^0 4-C5H5N^HC1 Et Cl^ Ph-N-Me Molecular quantities of the original materials were heated in an oil bath for a short time (30 min.) at 140°C. The pyridine... and methyl phenyl urea chloride. It was obtained in a pure state by recrystallization from gasoline and melted at 104°C. which was the melting point C~0 C5H5N > When molecular quantities of each compound were mixed in a lagge test tube and heated...

Brewster, Ray Q.

1915-01-01

192

Nonaaqua­praseodymium triiodide–thio­urea (1/2)  

PubMed Central

The title compound, [Pr(H2O)9]I3·2CS(NH2)2, an adduct of nona­aqua­praseodymium triiodide with two thio­urea mol­ecules, is composed from [Pr(H2O)9]3+ cations (polyhedron: monocapped tetra­gonal anti­prism), noncoordinated thio­urea mol­ecules and iodide anions. The components are evidently connected by hydrogen bonds but in the presence of heavy atoms water H atoms have not been located. The complex cation and one of the two independent iodide anions are located on a twofold axis. PMID:22346801

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

2012-01-01

193

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

PubMed

Diesel engine emissions for on-road, stationary and marine applications are regulated in the United States via standards set by the Environmental Protection Agency (EPA). A major component of diesel exhaust that is difficult to reduce is nitrogen oxides (NOx). Selective catalytic reduction (SCR) has been in use for many years for stationary applications, including external combustion boilers, and is promising for NOx abatement as a retrofit for mobile applications where diesel compression ignition engines are used. The research presented in this paper is the first phase of a program focused on the reduction of NOx by use of a stand-alone urea injection system, applicable to marine diesel engines typical of work boats (e.g., tugs). Most current urea SCR systems communicate with engine controls to predict NOx emissions based on signals such as torque and engine speed, however many marine engines in use still employ mechanical injection technology and lack electronic communication abilities. The system developed and discussed in this paper controls NOx emissions independentof engine operating parameters and measures NOx and exhaust flow using the following exhaust sensor inputs: absolute pressure, differential pressure, temperature, and NOx concentration. These sensor inputs were integrated into an independent controller and open loop architecture to estimate the necessary amount of urea needed, and the controller uses pulse width modulation (PWM) to power an automotive fuel injector for airless urea delivery. The system was tested in a transient test cell on a 350 hp engine certified at 4 g/bhp-hr of NOx, with a goal of reducing the engine out NOx levels by 50%. NOx reduction capabilities of 41-67% were shown on the non road transient cycle (NRTC) and ICOMIA E5 steady state cycles with system optimization during testing to minimize the dilute ammonia slip to cycle averages of 5-7 ppm. The goal of 50% reduction of NOx can be achieved dependent upon cycle. Further research with control optimization, urea distribution and possible use of oxidation catalysts is recommended to improve the NOx reduction capabilities while minimizing ammonia slip. PMID:19544914

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

2009-05-15

194

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

195

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

PubMed Central

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

2014-01-01

196

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

PubMed

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

Zarzyka, Iwona

2014-01-01

197

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

198

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

PubMed

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

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

2007-04-01

199

Combustion Technology Outreach  

NASA Technical Reports Server (NTRS)

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

1995-01-01

200

Carbon black enriched combustion  

SciTech Connect

A process for combustion of carbon black enriched gaseous hydrocarbon fuels is described comprising: entraining a plurality of carbon black particles in a carrier fluid, forming a carbon black/carrier fluid mixture; injecting said carbon black/carrier fluid mixture through a center nozzle of a fluid injector into a combustion chamber, said fluid injector having an outer nozzle concentrically disposed around said center nozzle forming an annular chamber between said center nozzle and said outer nozzle; injecting at least a first portion of a gaseous hydrocarbon fuel through said annular chamber into said combustion chamber forming a carbon black enriched gaseous hydrocarbon fuel; mixing said carbon black enriched gaseous hydrocarbon fuel with combustion air, forming a fuel/air mixture; and igniting said fuel/air mixture.

Joshi, M.L.; Tester, M.E.

1993-06-29

201

COMBUSTION - RISK MANAGEMENT  

EPA Science Inventory

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

202

Fluidized coal combustion  

NASA Technical Reports Server (NTRS)

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

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

1979-01-01

203

DEVELOPMENT OF ACTIVATED CARBONS FROM COAL COMBUSTION BY-PRODUCTS  

Microsoft Academic Search

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

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

2002-01-01

204

DEVELOPMENT OF ACTIVATED CARBONS FROM COAL COMBUSTION BY-PRODUCTS  

Microsoft Academic Search

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

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

2003-01-01

205

40 CFR 721.9900 - Urea, condensate with poly[oxy(methyl-1,2-ethanediyl)]-?- (2-aminomethylethyl)-?-(2-amino...  

Code of Federal Regulations, 2010 CFR

...2010-07-01 2010-07-01 false Urea, condensate with poly[oxy(methyl-1...Specific Chemical Substances § 721.9900 Urea, condensate with poly[oxy(methyl-1...reporting. (1) The chemical substance urea, condensate with...

2010-07-01

206

New Routing Metrics for ADHOC Network Routing Protocols  

NASA Astrophysics Data System (ADS)

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

Reddy, P. C.

2014-07-01

207

Coal combustion system  

DOEpatents

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

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

1988-01-01

208

Thermoluminescent dosimetric comparison for two different MgB4O7:Dy production routes  

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

209

Route 66 Oral Histories  

NSDL National Science Digital Library

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

210

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

Code of Federal Regulations, 2013 CFR

...418.30 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS FERTILIZER MANUFACTURING POINT SOURCE CATEGORY Urea Subcategory § 418.30 Applicability; description of the urea...

2013-07-01

211

40 CFR 721.6440 - Polyamine urea-for-malde-hyde condensate (specific name).  

Code of Federal Regulations, 2010 CFR

...Environment 30 2010-07-01 2010-07-01 false Polyamine urea-for-malde-hyde condensate (specific name). 721.6440...Uses for Specific Chemical Substances § 721.6440 Polyamine urea-for-malde-hyde condensate (specific name)....

2010-07-01

212

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

213

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

214

New urea-absorbing polymers for artificial kidney machines  

NASA Technical Reports Server (NTRS)

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

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

1975-01-01

215

Urea retention and uptake by avocado and apple leaves  

Microsoft Academic Search

Solution retention by avocado (Persea americana cv. Fuerte) and apple (Mallus domestica Burkh. cv. Anna) leaves was measured by weight gain of detached leaves after dipping them in solutions of two surfactants and by analysis of various concentrations of urea retained at zero time on surfaces of attached leaves. Linear regression equations were calulated, relating leaf area and retention of

Isaac Klein; Shmuel Zilkah

1986-01-01

216

Seasonal Variation and Response to Osmotic Challenge in Urea  

E-print Network

employed to prevent excessive water loss. In hydrated amphib- ians, urea is usually maintained at low, with a low abundance prevailing in the fall and winter, and higher levels occurring in the spring. The latter is accomplished by reducing glomerular filtration rate (GFR), adjusting the secretion

Lee Jr., Richard E.

217

IRIS Toxicological Review of Urea (Interagency Science Consultation Draft)  

EPA Science Inventory

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

218

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

219

Use of Two Sulfonyl Urea Herbicides in Lowbush Blueberry  

Microsoft Academic Search

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

Klaus I. N. Jensen; Eric G. Specht

2004-01-01

220

Chiral ?-Iodoamines by Urea-Catalyzed Iodocyclization of Trichloroacetimidates  

PubMed Central

Highly enantioselective vicinal iodoamination of olefins is accomplished through the iodocyclization of alkenyl trichloroacetimidates catalyzed by a new chiral Schiff-base urea derivative. The resulting products are converted readily to a variety of polyfunctional amine-containing chiral building blocks. PMID:24416631

Brindle, Cheyenne S.; Yeung, Charles S.

2013-01-01

221

Leaching and transformation of urea in dry and wet soils as affected by irrigation water  

Microsoft Academic Search

Summary  The leaching losses of urea in dry and wet soils as affected by the irrigation water, were studied in 90 cm long and 5 cm\\u000a diameter plexiglass columns. In dry sandy loam soil urea leached with irrigation water and peaks of urea were observed with\\u000a water front but in sandy soil the wetting front moved faster leaving the urea peak

Mahendra Singh; D. S. Yadav; Vinod Kumar

1984-01-01

222

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

Microsoft Academic Search

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

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

2004-01-01

223

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

NASA Technical Reports Server (NTRS)

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

Wydeven, T.; Leban, M.

1973-01-01

224

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

Microsoft Academic Search

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

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

2006-01-01

225

Urea on Flaked Soybean Hulls as a Protein Replacement for Dairy Cows1  

Microsoft Academic Search

In Experiment I a Latin square design was used to study the utilization of urea nitrogen adsorbed on flaked soybean hulls in normal rations of high producing dairy cows. Concentrates containing urea, urea with supplemental minerals, or soybean meal as the protein supplement were fed with corn silage and alfalfa in a total ration of approximately 17% crude protein. Both

S. C. Peyton; H. R. Conrad

1978-01-01

226

Role of urea in the postprandial urine concentration cycle of the insectivorous bat Antrozous pallidus.  

PubMed

Insectivorous bats, which feed once daily, produce maximally concentrated urine only after feeding. The role of urea as an osmolyte in this process was investigated in pallid bats (Antrozous pallidus) in the laboratory. Following a 24-h fast, plasma and urine were sampled before and 2 h after feeding in postprandial (PP) animals and before and 2 h after similar treatment without feeding in nonfed (NF) animals. Food consumption by PP animals and handling of NF animals had no effect on blood water content as measured by hematocrit and plasma oncotic pressure. Food consumption increased both plasma osmolality (P(osm)) and plasma urea (P(urea)) by as much as 15%. Food consumption also increased urine osmolality (U(osm)) and urine urea (U(urea)) by 50-100%. Feeding increased U(osm) regardless of changes in P(osm), and elevation of U(osm) resulted primarily from increased U(urea). In NF bats, P(osm) and P(urea) were unchanged, while U(osm) and U(urea) increased by as much as 25%. Again, increased U(osm) resulted primarily from increased U(urea). The PP urine concentration cycle of pallid bats resulted from increased urea excretion in response to apparent rapid urea synthesis. Bats rapidly metabolized protein and excreted urea following feeding when body water was most plentiful. PMID:15123201

Bassett, John E

2004-02-01

227

Urea in the Tributaries of the Chesapeake and Coastal Bays of Maryland  

Microsoft Academic Search

Concentrations of dissolved urea were monitored in several Chesapeake Bay tributaries from 1998 to 2002. Urea is a commonly used agricultural fertilizer and is also a breakdown product of poultry manure, which is used as an additional source of fertilizer throughout the watershed. Two trends were apparent. First, in several of the tributaries, seasonal peaks in ambient urea concentration coincided

Patricia M. Glibert; T. Mark Trice; Bruce Michael

2005-01-01

228

ORIGINAL PAPER Osmotic and metabolic responses to dehydration and urea-loading  

E-print Network

ORIGINAL PAPER Osmotic and metabolic responses to dehydration and urea-loading in a dormant Abstract Physiological responses to dehydration in amphibians are reasonably well documented, although urea did not differ initially; however, upon dehydration, metabolic rates decreased sooner in the urea

Lee Jr., Richard E.

229

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

230

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

231

Effect of feeding baled and stacked urea treated rice straw on the performance of crossbred cows  

Microsoft Academic Search

Crossbred dairy cows (2–4 lactations) in three groups (4 in each group) were fed with rations containing (1) untreated rice straw ad libitum plus 1kg concentrate supplement, (2) urea treated (4% urea; 50% moisture) rice straw stored in stack for 14 days, and (3) urea treated paddy straw compressed as bales and stored for 14 days. Extra concentrate supplement was

R. D. D Prasad; M. R Reddy; G. V. N Reddy

1998-01-01

232

Influence of Crop Residues and Organic Manures on the Hydrolysis of Urea in a Typic Haplustept  

Microsoft Academic Search

The emphasis on integrated use of organic amendments and fertilizers has made it imperative to study the effect of crop residues and organic manures on urea hydrolysis, which governs the release of N from urea fertilizer. Urea hydrolysis in soils is an enzymatic decomposition process facilitated by the extracellular enzyme urease. Our aim was to assess the influence of crop

M. S. Mavi; Balwinder Singh

2007-01-01

233

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

PubMed

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

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

2014-06-28

234

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

235

Advanced Subsonic Combustion Rig  

NASA Technical Reports Server (NTRS)

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

Lee, Chi-Ming

1998-01-01

236

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

237

Effect of rates of nitrogen and relative efficiency of sulphur-coated urea and nitrapyrin-treated urea in dry matter production and nitrogen uptake by rice  

Microsoft Academic Search

Summary A field experiment conducted for two rainy seasons (1974 and 1975) on a sandy clay loam soil at the Indian Agricultural Research Institute, New Delhi showed that at 100kg N\\/ha the apparent recovery of urea nitrogen by the rice crop was only 28%, which was raised to 41.7% by treating urea with Nitrapyrin and to 47.4% by coating urea

S. N. Sharma; Rajendra Prasad

1980-01-01

238

External combustion engine having a combustion expansion chamber  

NASA Astrophysics Data System (ADS)

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

Duva, Anthony W.

1993-03-01

239

Combustible structural composites and methods of forming combustible structural composites  

DOEpatents

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

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

2013-04-02

240

Combustible structural composites and methods of forming combustible structural composites  

DOEpatents

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

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

2011-08-30

241

Effects of treating rice straw with urea or urea and calcium hydroxide upon intake, digestibility, rumen fermentation and milk yield of dairy cows  

Microsoft Academic Search

Three, multiparous Holstein crossbred dairy cows with initial body weight of 385±19 kg were randomly allocated to 3 treatments of rice straw (T1 = untreated rice straw; T2 = 5.5% urea-treated rice straw (5 g urea in 100 ml water to 100 g air-dry (91% DM) straw); T3 = 2.2% urea+2.2% calcium hydroxide treated rice straw (2.0 g urea and 2.0 g Ca(OH)2 in 100 ml to

Metha Wanapat; Sineenart Polyorach; Kitsada Boonnop; Chaowarit Mapato; Anusorn Cherdthong

2009-01-01

242

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

PubMed Central

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

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

2014-01-01

243

Antipollution combustion chamber  

SciTech Connect

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

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

1981-01-27

244

Ames Hybrid Combustion Facility  

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

245

Thermodynamics and combustion modeling  

NASA Technical Reports Server (NTRS)

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

Zeleznik, Frank J.

1986-01-01

246

Effect of heating conditions during combustion synthesis on the characteristics of Ni 0.5 Zn 0.5 Fe 2 O 4 nanopowders  

Microsoft Academic Search

Ni-Zn ferrite powders were synthesized by combustion reaction. The effect of external conditions of heating on the characteristics of the resulting powders was evaluated. Two synthesis routes were studied. The first involved preheating on a hot plate at 300°C and subsequently heating in a muffle furnace at 700°C (RCPM). In the second route the powders (RCP) were heated directly to

A. C. F. M. Costa; E. Tortella; M. R. Morelli; M. Kaufman; R. H. G. A. Kiminami

2002-01-01

247

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

PubMed

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

Clayden, Jonathan; Lemiègre, Loïc; Helliwell, Madeleine

2007-03-30

248

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

249

Modelling routes towards learning goals  

Microsoft Academic Search

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

Colin Tattersall; José Janssen; Bert van den Berg; Rob Koper

2006-01-01

250

The Revised ARPANET Routing Metric  

Microsoft Academic Search

The ARPANBT routing metric was revised in July 1987, re- sulting in substantial performance improvements, especially in terms of user delay and effective network capacity. These revisions only affect the individual link costs (or metrics) on which the PSN (packet switching node) bases its rout- ing decisions. They do not affect the SPF (\\

A. Khanna; John A. Zinky

1989-01-01

251

Optimising Yacht Routes under Uncertainty  

Microsoft Academic Search

The planning of routes for sailing vessels is subject to uncertainty from the weather. This is particularly important in yacht racing where the accuracy of a weather prediction can determine the outcome of a race. With a perfect weather forecast it is possible to use the polar tables of a given yacht to compute a route that minimises its arrival

Andy Philpott; Andrew Mason

252

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

253

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

254

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

255

Studies in combustion dynamics  

SciTech Connect

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

Koszykowski, M.L. [Sandia National Laboratories, Livermore, CA (United States)

1993-12-01

256

MODELLING PULVERISED COAL COMBUSTION USING A DETAILED COAL COMBUSTION MODEL  

Microsoft Academic Search

The ability to assess the combustion behaviour of internationally traded coals and accurately predict flame characteristics, stable species concentration, unburned carbon and pollutant emissions is of importance to the power generating industry. Despite recent advances in coal combustion modelling detailed understanding is still lacking on the exact role of the coal maceral content on the combustion process. Here, a CFD-based

R. I. BACKREEDY; L. M. FLETCHER; L. MA; M. POURKASHANIAN; A. WILLIAMS

2006-01-01

257

Structure and Dynamics of Urea/Water Mixtures Investigated by Vibrational Spectroscopy and Molecular Dynamics Simulation  

PubMed Central

Urea/water is an archetypical “biological” mixture, and is especially well known for its relevance to protein thermodynamics, as urea acts as a protein denaturant at high concentration. This behavior has given rise to an extended debate concerning urea’s influence on water structure. Based on a variety of methods and of definitions of water structure, urea has been variously described as a structure-breaker, a structure-maker, or as remarkably neutral towards water. Because of its sensitivity to microscopic structure and dynamics, vibrational spectroscopy can help resolve these debates. We report experimental and theoretical spectroscopic results for the OD stretch of HOD/H2O/urea mixtures (linear IR, 2DIR, and pump-probe anisotropy decay) and for the CO stretch of urea-D4/D2O mixtures (linear IR only). Theoretical results are obtained using existing approaches for water, and a modification of a frequency map developed for acetamide. All absorption spectra are remarkably insensitive to urea concentration, consistent with the idea that urea only very weakly perturbs water structure. Both this work and experiments by Rezus and Bakker, however, show that water’s rotational dynamics are slowed down by urea. Analysis of the simulations casts doubt on the suggestion that urea immobilizes particular doubly hydrogen bonded water molecules. PMID:23841646

Carr, J. K.; Buchanan, L. E.; Schmidt, J. R.; Zanni, M. T.; Skinner, J. L.

2013-01-01

258

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. PMID:22418868

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

259

Analysis of Blood and Salivary Urea Levels in Patients Undergoing Haemodialysis and Kidney Transplant  

PubMed Central

Aims and Objectives: To determine correlation between the Salivary Urea levels with that of Blood Urea levels. Materials and Methods: Subjects were selected from patients undergoing haemodialysis and patients who had underwent kidney transplantation at Ashwini Hospitals Guntur. The study comprised of 45 patients, of which Haemodialysis group (HD) with 20 patients, Transplant (T) group with 15 patients and 10 patients in control group. Samples of blood and saliva were taken from all the patients to assess the Blood Urea Nitrogen (BUN) and Salivary Urea (SU) levels respectively under strict aseptic precautions. Blood was collected just prior to the dialysis in HD group and in renal transplant (T) patients during their review visit. Informed consent was taken from patients and ethical committee approval taken. Results: There was a statistically significant difference between Blood Urea and Salivary Urea levels in the HD and T group (p<0.05). There was a statistically significant difference between T and Control group with respect to Blood Urea and Salivary Urea levels. The salivary urea levels are slightly higher than blood urea levels in all the study groups. Conclusion: The salivary urea tests can be used in place of blood tests as a non invasive diagnostic tool. Thus, preventing the unnecessary and periodic withdraw of blood which is not only cumbersome but also leads to recurrent infections. PMID:25177630

A, Ravi Kiran; Y, Samata; N, Purnachandrarao Naik; A, Vijay Kumar

2014-01-01

260

Autonomous routing algorithms for networks with wide-spread failures : a case for differential backlog routing  

E-print Network

We study the performance of a differential backlog routing algorithm in a network with random failures. Differential Backlog routing is a novel routing algorithm where packets are routed through multiple paths to their ...

Khan, Wajahat Faheem

2008-01-01

261

Characterization and Electrochemical Studies of LiMn 2 O 4 Cathode Materials Prepared by Combustion Method  

Microsoft Academic Search

A combustion method using urea as a fuel has been developed for the synthesis of the spinel LiMn2O4 around 500°C. Physical features of the products were identified by X-ray photoelectron spectroscopy, X-ray diffractometry, Raman scattering and FTIR spectroscopy. Cells were fabricated with Li\\/\\/LiMn2O4 and C\\/\\/LiMn2O4 in nonaqueous organic electrolyte and their performances were studied. A kinetic profile for diffusion of

S. Chitra; P. Kalyani; T. Mohan; R. Gangadharan; B. Yebka; S. Castro-Garcia; M. Massot; C. Julien; M. Eddrief

1999-01-01

262

Visible and NIR luminescence of nanocrystalline ?-Ga 2O 3:Er 3+ prepared by solution combustion synthesis  

Microsoft Academic Search

In this paper we report on facile solution combustion synthesis of erbium doped ?-Ga2O3 with urea as fuel. The product was characterized using powder X-ray diffraction and transmission electron microscopy (TEM). X-ray diffraction and TEM showed that the material is nanostructured. Luminescence properties of ?-Ga2O3:Er are studied with excitation in near infrared (Nd:YAG laser at 1064nm) and visible (argon laser

Tomislav Biljan; Andreja Gajovi?; Zlatko Mei?

2008-01-01

263

Combuster. [low nitrogen oxide formation  

NASA Technical Reports Server (NTRS)

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

Mckay, R. A. (inventor)

1978-01-01

264

Toxicology of Biodiesel Combustion products  

EPA Science Inventory

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

265

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...

266

Urea Cycle Enzyme Activities of Liver of the African Lion  

Microsoft Academic Search

IN the course of a continuous survey1,2 on the occurrence and levels of activity of ornithine-urea cycle3 enzymes, an unexpected opportunity was afforded for quantitative measurement of these activities in the instance of the African lion, Felis leo. At the Vilas Park Zoo in Madison (Wisconsin) the director, Mr. Dan Watson, decided that an infirm male lion about twelve years

G. W. Brown

1966-01-01

267

Growth of urea crystals by physical vapor transport  

NASA Technical Reports Server (NTRS)

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

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

1985-01-01

268

The response of rice straw varieties to urea treatment  

Microsoft Academic Search

Sixteen rice straw varieties comprising 6 single-crop and 10 double-crop varieties were treated with 40g\\/l urea solution (50g straw per 200ml of solution) for 21 days at 27°C and total and insoluble ash, crude protein, neutral detergent fibre and in vitro digestibility (IVD) were measured after samples were dried at 60°C to constant weight. The mean IVD values across treatments

J. Vadiveloo; J. G. Fadel

2009-01-01

269

Electrical properties of Ni\\/YSZ cermets obtained through combustion synthesis  

Microsoft Academic Search

The synthesis of Ni\\/YSZ cermet with controlled microstructural characteristics presents a lot of interest for many solid-state electrochemical applications. These materials are generally obtained by reducing poorly sintered mixtures of YSZ with nickel oxide by hydrogen. We recently proposed an alternative route based on a thermite reaction performed in a combustion regime. This method makes it possible, in one step,

U Anselmi-Tamburini; G Chiodelli; M Arimondi; F Maglia; G Spinolo; Z. A Munir

1998-01-01

270

A decade of combustion research  

Microsoft Academic Search

The Advanced Combustion Engineering Research Center (ACERC) at Brigham Young University and the University of Utah, in cooperation with other universities, 37 industrial members and six governmental members, has marked a decade of combustion research. This review emphasizes the contributions of ACERC over this past decade. While the state-of-the-art relating to fossil fuel combustion is discussed, the paper does not

L. Douglas Smoot

1997-01-01

271

46 CFR 45.175 - Applicable routes.  

Code of Federal Regulations, 2011 CFR

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

2011-10-01

272

46 CFR 45.175 - Applicable routes.  

Code of Federal Regulations, 2010 CFR

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

2010-10-01

273

46 CFR 45.175 - Applicable routes.  

Code of Federal Regulations, 2013 CFR

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

2013-10-01

274

46 CFR 45.175 - Applicable routes.  

Code of Federal Regulations, 2012 CFR

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

2012-10-01

275

Molecular diagnosis of urea cycle disorders: current global scenario.  

PubMed

Urea cycle disorders are a group of inborn error of metabolism, characterized by hyperammonemia, metabolic alkalosis and clinical features of encephalopathy. These are among the commonest types of inborn errors of metabolism with a frequency of 1 in 8,000 to 1 in 30,000 in different population. This encompasses 5 major disorders, corresponding with deficiency of each step in the urea cycle, namely ornithine transcarbamoylase (OTC) deficiency, argininosuccinate lyase (ASL) deficiency, carbamoyl phosphate synthetase (CPS) deficiency, citrullinemia and argininemia. The most important clinical presentation is neurological abnormalities. The severity of UCD is correlated to extent of hyperammonemia. Early diagnosis and treatment are essential for successful patient outcome. Various modalities of treatment have been recommended; namely, treatment aimed at reducing ammonia level, including drugs like sodium benzoate and sodium phenyl butyrate, neuroprotective strategies, low protein diet, liver transplantation and hepatocyte transplantation. Molecular diagnosis is important to identify the pathogenesis of these disorders as well as it helps in prognosis. This review intends to summarize the important aspects of molecular diagnostic studies on urea cycle disorders. PMID:24772957

Vaidyanathan, K

2013-10-01

276

Enzymatic urea adaptation: lactate and malate dehydrogenase in elasmobranchs.  

PubMed

Lactate dehydrogenase (LDH) and malate dehydrogenase (MDH) electrophoretic tissue patterns of two different orders of Elasmobranchii: Carchariniformes (Galeus melanostomus and Prionace glauca) and Squaliformes (Etmopterus spinax and Scymnorinus licha) were studied. The number of loci expressed for these enzymes was the same of other elasmobranch species. Differences in tissue distribution were noted in LDH from G. melanostomus due to the presence of an additional heterotetramer in the eye tissue. There were also differences in MDH. In fact, all the tissues of E. spinax and G. melanostomus showed two mitochondrial bands. Major differences were noted in the number of isozymes detected in the four compared elasmobranchs. The highest polymorphism was observed in E. spinax and G. melanostomus, two species that live in changeable environmental conditions. The resistance of isozymes after urea treatment was examined; the resulting patterns showed a quite good resistance of the enzymes, higher for LDH than MDH, also at urea concentration much greater than physiological one. These results indicated that the total isozyme resistance can be considered higher in urea accumulators (such as elasmobranchs) than in the non-accumulators (such as teleosts). PMID:16497106

Laganà, G; Bellocco, E; Mannucci, C; Leuzzi, U; Tellone, E; Kotyk, A; Galtieri, A

2006-01-01

277

Developing Hypothetical Inhibition Mechanism of Novel Urea Transporter B Inhibitor  

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

278

Diagnosis and treatment of urea cycle disorder in Japan.  

PubMed

Urea cycle disorder (UCD) is an inborn error of the metabolic pathway producing urea from ammonia, which occurs primarily in the liver. Decreased excretion of nitrogen in the urea cycle due to deficiency of carbamoyl phosphate synthase I (CPSI), ornithine transcarbamylase (OTC), argininosuccinate synthase (ASS), argininosuccinate lyase (ASL), and N-acetyl glutamate synthase (NAGS) causes hyperammonemia. We examined the clinical manifestations, treatment, and prognosis of 177 patients with UCD from January 1999 to March 2009 in Japan. Compared with a previous study conducted in Japan, a larger number of patients survived without mental retardation, even when the peak blood ammonia was >360??mol/L. In those with peak blood ammonia >360??mol/L, an indicator of poor prognosis, the frequency of convulsions, mental retardation, brain abnormality on magnetic resonance imaging, hemodialysis, liver transplantation, and intake of non-protein formulas was significantly higher than in those with peak blood ammonia <360??mol/L. In this article, we have reported the current state of UCD to evaluate prognosis and its relationship with peak blood ammonia and hemodialysis. PMID:25039902

Nakamura, Kimitoshi; Kido, Jun; Mitsubuchi, Hiroshi; Endo, Fumio

2014-08-01

279

Developing hypothetical inhibition mechanism of novel urea transporter B inhibitor.  

PubMed

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

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

2014-01-01

280

WASTE COMBUSTION SYSTEM ANALYSIS  

EPA Science Inventory

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

281

COMBUSTION OF HAZARDOUS WASTE  

EPA Science Inventory

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

282

Combustion Fundamentals Research  

NASA Technical Reports Server (NTRS)

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

1984-01-01

283

Fragments, Combustion and Earthquakes  

E-print Network

This paper is devoted to show the advantages of introducing a geometric viewpoint and a non extensive formulation in the description of apparently unrelated phenomena: combustion and earthquakes. Here, it is shown how the introduction of a fragmentation analysis based on that formulation leads to find a common point for description of these phenomena

Oscar Sotolongo-Costa; Antonio Posadas

2005-03-16

284

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

285

Internal combustion engine  

Microsoft Academic Search

An internal combustion engine is disclosed which includes active cylinders being always active and inactive cylinders being inactive when the engine load is below a predetermined value. The engine has an intake passage divided into first and second branches connected to active and inactive cylinders, respectively. The second branch is provided near its inlet with a stop valve and is

Y. Etoh; T. Tanaka

1982-01-01

286

Spray combustion stability project  

NASA Technical Reports Server (NTRS)

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

Jeng, San-Mou; Litchford, Ron J.

1992-01-01

287

Combustion properties of biomass  

Microsoft Academic Search

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

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

1998-01-01

288

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

289

Monopropellant combustion system  

NASA Technical Reports Server (NTRS)

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

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

2005-01-01

290

Sewage sludge combustion  

Microsoft Academic Search

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

J. Werther; T. Ogada

1999-01-01

291

Project Sponsors: UCI Combustion  

E-print Network

Microturbine Generator." Journal of Eng. Gas Turb. & Power 130 (1). OVERVIEW Fluid dynamics and chemical. McDonell.(2013) "Impact of Ethane, Propane, and Diluent Content in Natural Gas on the NOx emissions of a Commercial Microturbine Generator". 8th U. S. National Combustion Meeting. · R. Hack and V. McDonell. (2008

Mease, Kenneth D.

292

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

Microsoft Academic Search

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

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

1990-01-01

293

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

294

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

295

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

296

Past Tense Route Priming  

PubMed Central

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

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

2013-01-01

297

Understanding Route Aggregation Geoffrey G. Xie  

E-print Network

.1.0.0/24, 10.1.1.0/24, ..., 10.1.15.0/24. Rather than advertising these 16 prefixes to router Z, route the more specific routes (e.g., 10.1.0.0/24, 10.1.1.0/24, etc.) become child or contributing routes of at least one of its child routes. The announcement will stop if no child route is present. Route

298

Emissions from syngas combustion  

SciTech Connect

Gasification technology has matured to the point that previously-held hesitations regarding performance and availability have given way to acceptance of the technology for energy generation. Indeed, the past few years have seen a significant increase in the number of gasifiers installed for generation of power and heat, and the number of installations is expected to increase dramatically over the next several decades as demand for efficient and environmentally sound energy generation increases. It is valuable to consider the environmental impact of this new generation of energy production systems, specifically release of gaseous emissions from combustion of the synthesis gas produced by gasification. Emissions from syngas combustion in turbines, engines and boilers are discussed in this review. The types of emissions considered include the unburned fuel components and partially oxidized species, nitrogen and sulfur-containing gases, volatile organic compounds, and other trace elements. Combustion of synthesis gas, in general, produces lower emissions for heat and power generation than conventional liquid and solid fuels. The composition of the syngas strongly influences the level of emissions. Hydrogen and carbon monoxide in synthesis gases results in elevated combustion temperature that facilitates the thermal formation of NO and NO{sub 2}. In contrast, higher temperatures promote complete combustion and reduce the emission of organic volatiles, which are formed mainly from minor fractions of hydrocarbons in synthesis gases. Particulate matter, metallic compounds and other undesired pollutants are usually removed before firing synthesis gases for heat and power production. Therefore, integrated gasification and combined cycle systems are more environmentally friendly than conventional power generation systems.

Whitty, K.J.; Zhang, H.R.; Eddings, E.G. [University of Utah, Salt Lake City, UT (United States). Inst. for Clean & Secure Energy

2008-07-01

299

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

300

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

301

Urea: An important piece of Water Soluble Organic Nitrogen (WSON) over the Eastern Mediterranean.  

PubMed

The role of atmospheric urea on the biogeochemical cycle of Water Soluble Organic Nitrogen (WSON) in the Eastern Mediterranean was assessed by collecting and analyzing wet and dry deposition samples and size segregated aerosols during a one year period (2006). In rain water volume weighted mean (VWM) concentration of urea was found equal to 5.5?M. In atmospheric particles the average concentration of urea in coarse and fine mode was 0.9±1.9nmol N m(-3) (median 0.0nmol N m(-3)) and 2.2±3.0nmol N m(-3) (median 1.1nmol N m(-3)), respectively. The percentage contribution of urea to WSON fraction was 0% and 20% in coarse and fine particles respectively. On an annual basis 0.81mmol m(-2) and 1.78mmol m(-2) of urea were deposited via wet and dry deposition, contributing to WSON by 10% and 11% respectively. Regression analysis of urea with the main ions and trace metals measured in parallel suggest that soil and anthropogenic activities significantly contribute to atmospheric urea. Comparison of dry deposition of urea using size segregated deposition velocities with urea collected on a glass bead collector suggested the existence of significant fraction of urea in the gas phase. PMID:21903240

Violaki, Kalliopi; Mihalopoulos, Nikos

2011-10-15

302

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

303

The effect of urea infusion on the urinary concentrating mechanism in protein-depleted rats.  

PubMed Central

To explore the role of urea in the urinary concentrating mechanism, the contents of vasa recta, Henle's descending limbs and collecting ducts were sampled by micropuncture of the renal papilla before and after infusion of urea in 10 protein-depleted rats. Eight protein-depleted rats not given urea were similarly studied as a control group. After urea administration, osmolality and the concentrations of urea and nonurea solute of urine from both exposed and contralateral kideny increased significantly. The osmolality and urea concentration of fluid from the end of Henle's descending limb and vasa recta plasma and the tubule fluid-to-plasma inulin ratio in the end-descending limb all increased significantly after urea infusion. We interpret these observations to indicate that urea enhances urinary concentration by increasing the abstraction of water from the juxtamedullary nephron (presumably the descending limb), in agreement with the prediction of recent passive models of the urinary concentrating mechanism. However, the concentration of urea in fluid from the descending limb after urea infusion was high (261 plus or minus 31 mM) and the difference in solium concentration between descending limb fluid and vasa recta was small and statistically insignificant. PMID:1127107

Pennell, J P; Sanjana, V; Frey, N R; Jamison, R L

1975-01-01

304

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

305

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

PubMed

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

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

2014-06-01

306

Research avenues in combustion aerodynamics  

SciTech Connect

Practical combustion systems incorporate interdependent phenomena of three-dimensional multicomponent flow fields with complex multiphase chemical kinetics, evaporation and heat transfer processes all occurring simultaneously. An overview is presented here of the prospects for improved understanding of combustion processes, with particular emphasis on fluid dynamics and modeling, as applied to practical combustion systems. Extensive measurements should cover a wide range of physical variables, and include mean and time-dependent data and correlations obtained nonintrusively, so as to aid the modeler. Regarding combustion studies, after success with fluid dynamic model laws with a given fuel, extension to a wider range of fuels is required. Applied combustion research needs include the clean and efficient combustion of fossil fuels and future low-grade liquid and solid fuels, and the associated reduction of pollution through combustion control. Fundamental combustion research needs to be done in the areas of interactions between turbulence and kinetics, nonintrusive optical diagnostics, computer model development, gas and solid phase kinetics, droplet/particle cloud combustion, soot formation and chemistry, and flame structure. Both experimental and theoretical combustion engineers need greater understanding of combustion processes.

Lilley, D.G. [Oklahoma State Univ., Stillwater, OK (United States). School of Mechanical and Aerospace Engineering

1994-12-31

307

Collective learning in route navigation.  

PubMed

In a recent paper,(1) we examined how experience of repeatedly flying with a specific partner influences pigeons' subsequent navigational decision-making in larger flocks. We found that pairs develop into a "behavioral unit" through their shared experience of joint flights, acquiring a single idiosyncratic route during training, and then forming spatially distinct subgroups when flying with other pairs. Further, differences between the route preferences of different pairs appear to be reconciled through the same mechanisms as those that apply to individuals. Here we examine in more detail the development of route preferences in pairs, as an example of "collective learning." We find that pairs acquire routes more quickly, but with less precision, than individuals. We use these results to hypothesize on the advantages and limitations of solving problems collectively. PMID:24505504

Flack, Andrea; Biro, Dora

2013-11-01

308

Network knowledge and route choice  

E-print Network

Models of urban traveler route choice are reviewed in the context of Intelligent Transportation Systems, particularly Advanced Traveler Information S ystems. Existing models suffer from assumptions of perfect information ...

Ramming, Michael Scott

2002-01-01

309

Delaware Route 14, Rehoboth Bypass.  

National Technical Information Service (NTIS)

The report considers the proposed addition of two travel lanes parallel to the existing two lane Route 14 and separated by a median. Two commercial establishments and six residential homes will require relocation. Further adverse affects are inconvenience...

1971-01-01

310

New Techniques for Geographic Routing  

E-print Network

As wireless sensor networks continue to grow in size, we are facedwith the prospect of emerging wireless networks with hundreds orthousands of nodes. Geographic routing algorithms are a promisingalternative to tradition ...

Leong, Ben

2006-06-14

311

New techniques for geographic routing  

E-print Network

As wireless sensor networks continue to grow in size, we are faced with the prospect of emerging wireless networks with hundreds or thousands of nodes. Geographic routing algorithms are a promising alternative to tradition ...

Leong, Ben Wing Lup

2006-01-01

312

Protocol independent adaptive route update for VANET.  

PubMed

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

Rasheed, Asim; Ajmal, Sana; Qayyum, Amir

2014-01-01

313

Protocol Independent Adaptive Route Update for VANET  

PubMed Central

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

Rasheed, Asim; Qayyum, Amir

2014-01-01

314

Route Optimization in IP Networks  

Microsoft Academic Search

The performance and reliability of the Internet depend, in large part, on the operation of the underlying routing protocols.\\u000a Today’s IP routing protocols compute paths based on the network topology and configuration parameters, without regard to the\\u000a current traffic load on the routers and links. The responsibility for adapting the paths to the prevailing traffic falls to\\u000a the network operators

Jennifer Rexford

315

Efficient Routing using Class Climbing  

Microsoft Academic Search

This paper concentrates on a routing algorithm that is adaptive and avoids deadlocks and starvation. It is a general store-and-forward packet router that has been developed to be used as part of a distributed runtime system for Concurrent Clean, an experimental, lazy, higher-order parallel functional programming language based on term graph rewriting. The routing algorithm is based on the one

Marco Kesseler

1993-01-01

316

Fairness in optimal routing algorithms  

E-print Network

. Tsei Dr. Pierce E. Cantrell A study of fairness in multiple path optimal routing algorithms is discussed. Fair- ness measures are developed to evaluate multiple path routing in virtual circuit and datagram implementations. Several objective.... One objective function is shown to have perfect fairness for virtual circuits. The objective function optimized was shown to have little effect on the average packet delay. To my parents and my brother ACKNOWLEDGMENTS I wish to express my...

Goos, Jeffrey Alan

2012-06-07

317

Infrared and visible emission of Er 3+ in combustion-synthesized CaAl 2O 4 phosphors  

Microsoft Academic Search

New near-infrared luminescent, monoclinic CaAl2O4:Er3+ phosphor was prepared by using the combustion route at furnace temperatures as low as 500°C in a few minutes. Combustion synthesized phosphor has been well characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive analysis of X-ray (EDAX) mapping studies. The luminescence spectra of Er3+-doped calcium aluminate were studied at UV (380nm), vis

Vijay Singh; R. P. S. Chakradhar; Isabelle Ledoux-Rak; Laurent Badie; Fabienne Pelle; Svetlana Ivanova

2009-01-01

318

Combustion engine system  

NASA Technical Reports Server (NTRS)

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

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

1986-01-01

319

Combustion powered linear actuator  

DOEpatents

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

Fischer, Gary J. (Albuquerque, NM)

2007-09-04

320

Spray atomization and combustion  

NASA Technical Reports Server (NTRS)

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

Faeth, G. M.

1986-01-01

321

Secure Route Discovery for QoS-Aware Routing in AdHoc Networks  

Microsoft Academic Search

We address the problem of securing the route discovery for Quality-of-Service (QoS)-aware routing in ad hoc networks. We provide a specification of secure route discovery for QoS-aware routing. We propose a reactive secure routing protocol, SRP-QoS, to defend against adversaries manipulating link and route metrics and, thus, prevent them from influencing the route selection. SRP-QoS ensures the accuracy of the

Panagiotis Papadimitratos; Zygmunt J. Haas

2005-01-01

322

Dynamic urea bond for the design of reversible and self-healing polymers  

NASA Astrophysics Data System (ADS)

Polymers bearing dynamic covalent bonds may exhibit dynamic properties, such as self-healing, shape memory and environmental adaptation. However, most dynamic covalent chemistries developed so far require either catalyst or change of environmental conditions to facilitate bond reversion and dynamic property change in bulk materials. Here we report the rational design of hindered urea bonds (urea with bulky substituent attached to its nitrogen) and the use of them to make polyureas and poly(urethane-urea)s capable of catalyst-free dynamic property change and autonomous repairing at low temperature. Given the simplicity of the hindered urea bond chemistry (reaction of a bulky amine with an isocyanate), incorporation of the catalyst-free dynamic covalent urea bonds to conventional polyurea or urea-containing polymers that typically have stable bulk properties may further broaden the scope of applications of these widely used materials.

Ying, Hanze; Zhang, Yanfeng; Cheng, Jianjun

2014-02-01

323

Dynamic urea bond for the design of reversible and self-healing polymers.  

PubMed

Polymers bearing dynamic covalent bonds may exhibit dynamic properties, such as self-healing, shape memory and environmental adaptation. However, most dynamic covalent chemistries developed so far require either catalyst or change of environmental conditions to facilitate bond reversion and dynamic property change in bulk materials. Here we report the rational design of hindered urea bonds (urea with bulky substituent attached to its nitrogen) and the use of them to make polyureas and poly(urethane-urea)s capable of catalyst-free dynamic property change and autonomous repairing at low temperature. Given the simplicity of the hindered urea bond chemistry (reaction of a bulky amine with an isocyanate), incorporation of the catalyst-free dynamic covalent urea bonds to conventional polyurea or urea-containing polymers that typically have stable bulk properties may further broaden the scope of applications of these widely used materials. PMID:24492620

Ying, Hanze; Zhang, Yanfeng; Cheng, Jianjun

2014-01-01

324

Growth and properties of urea-doped triglycine sulfate (UrTGS) crytals  

NASA Astrophysics Data System (ADS)

This paper discusses the growth and properties of triglycine sulfate (TGS) crystals doped with urea. It was found that the normalized growth yield and pyroelectric and dielectric constants could be increased significantly by urea additions. TGS crystals doped with 5 and 10 wt% urea exhibited up to five times higher material figures of merit for infrared pyroelectric detectors compared with undoped TGS crystals. The Vickers hardness of doped crystals increased with urea content to about three times the undoped value in the [010] direction at 10 wt% urea. No significant increase in the hardness was found, however, in the [001] direction. Incorporation of urea in TGS crystals has been qualitatively estimated by Fourier transform infrared (FTIR) data.

Chang, Jiann-Min; Batra, A. K.; Lal, R. B.

1996-01-01

325

Transfer of urea from the blood to the rumen of sheep.  

PubMed

1. The rate of transfer of plasma urea-nitrogen to rumen ammonia was measured by infusion of 15NH4Cl and [15N]urea into sheep given brome grass (Bromus inermis) or lucerne (Medicago sativa) pellets. Urea was infused into the rumen or abomasum of two sheep given brome grass in order to increase the concentration of rumen ammonia. 2. From 6.2 to 9.8 g/d of plasma urea-N were transferred to the rumen of sheep given brome grass pellets and a measurement of 1.3 g nitrogen/d was obtained for a sheep given lucerne pellets. When urea was infused into the rumen of sheep given brome grass pellets the transfer was only 2.8--3.7 g N/d. 3. There was a significant negative correlation between the rate of transfer of plasma urea-N to the rumen and the concentration of rumen ammonia. PMID:666998

Kennedy, P M; Milligan, L P

1978-07-01

326

Spray combustion stability  

NASA Technical Reports Server (NTRS)

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

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

1995-01-01

327

Internal combustion engine using premixed combustion of stratified charges  

DOEpatents

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

Marriott, Craig D. (Rochester Hills, MI); Reitz, Rolf D. (Madison, WI

2003-12-30

328

Prediction of equilibrated urea in children on chronic hemodialysis.  

PubMed

Urea rebound (UR) after hemodialysis (HD) requires the use of equilibrated urea (Ceq) instead of immediate end-dialysis urea (Ct) for correct quantification of HD, which is impractical. A new formula for predicting Ceq in children is suggested in our study. Thirty eight standard pediatric HD sessions (single pool Kt/V = 1.70 +/- 0.35, K = 4.65 +/- 1.14 ml/min/kg, UF coeff. = 3.2-6.2 ml/h/mm Hg, t = 3.80 +/- 0.46 h) in 15 children (M: 6, F: 9), ages 14.5 +/- 3.28 years were analyzed. Blood samples were taken: before, 70 min from the start, at the end, and 60 min after the end of HD sessions. After correlating UR (20.32 +/- 7.74%) to various HD parameters, we found that it was mainly determined by HD efficiency parameters. Therefore we correlated Ceq to HD efficiency parameters (Ct, urea reduction ratio, Kt/V, and K/V) and found a very high correlation between Ct and Ceq (r = 0.973). Linear regression analysis was used to further investigate this relationship, and a new formula to predict Ceq from Ct was obtained (Ceq = 1.085 Ct + 0.729, R2 = 0.946, SE = 0.49, absolute residuals = 0.38 +/- 0.29 mmol/L). In a validation study (10 HD sessions with new set of urea blood samples) the results obtained by the new formula were compared with measured values of Ceq and those obtained by the Smye formulae. Values predicted by the new formula (9.91 +/- 2.92 mmol/L) were not significantly different from the measured values (10.33 +/- 3.44 mmol/L). Absolute error of the new formula was 0.78 +/- 0.73 mmol/L, median 0.65; ie., 6.93 +/- 5.3%, median 7.7%. Ceq predicted by the Smye formulae (10.95 +/- 4.18 mmol/L) also did not significantly differ from the measured values, but absolute error of predicted values was markedly higher (1.21 +/- 0.90 mmol/L, median 0.89; 11.73 +/- 7.72%, median 10.11%; p < 0.05). When predicted Ceq was used for calculating equilibrated Kt/V (eKt/V), the new formula resulted in lower absolute error (0.09 +/- 0.07, median 0.08) than the Smye method (0.14 +/- 0.08, median 0.12). We conclude that our simple formula is sufficiently accurate in predicting Ceq in standard pediatric HD and that it is more accurate than the existing Smye formulae, while requiring only pre- and post-HD urea samples. We suggest the use of the new formula for predicting Ceq, which can then be used instead of Ct for a more accurate estimation of double pool Kt/V, URR, V, and PCR. PMID:10826737

Marseni?, O D; Pavlici?, D; Peco-Anti?, A; Bigovi?, G; Jovanovi?, O

2000-01-01

329

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

PubMed

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

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

2001-10-01

330

Intermolecular interactions and 3D structure in cellulose-NaOH-urea aqueous system.  

PubMed

The dissolution of cellulose in NaOH/urea aqueous solution at low temperature is a key finding in cellulose science and technology. In this paper, (15)N and (23)Na NMR experiments were carried out to clarify the intermolecular interactions in cellulose/NaOH/urea aqueous solution. It was found that there are direct interactions between OH(-) anions and amino groups of urea through hydrogen bonds and no direct interaction between urea and cellulose. Moreover, Na(+) ions can interact with both cellulose and urea in an aqueous system. These interactions lead to the formation of cellulose-NaOH-urea-H2O inclusion complexes (ICs). (23)Na relaxation results confirmed that the formation of urea-OH(-) clusters can effectively enhance the stability of Na(+) ions that attracted to cellulose chains. Low temperature can enhance the hydrogen bonding interaction between OH(-) ions and urea and improve the binding ability of the NaOH/urea/H2O clusters that attached to cellulose chains. Cryo-TEM observation confirmed the formation of cellulose-NaOH-urea-H2O ICs, which is in extended conformation with mean diameter of about 3.6 nm and mean length of about 300 nm. Possible 3D structure of the ICs was proposed by the M06-2X/6-31+G(d) theoretical calculation, revealing the O3H···O5 intramolecular hydrogen bonds could remain in the ICs. This work clarified the interactions in cellulose/NaOH/urea aqueous solution and the 3D structure of the cellulose chain in dilute cellulose/NaOH/urea aqueous solution. PMID:25111839

Jiang, Zhiwei; Fang, Yan; Xiang, Junfeng; Ma, Yanping; Lu, Ang; Kang, Hongliang; Huang, Yong; Guo, Hongxia; Liu, Ruigang; Zhang, Lina

2014-08-28

331

Influence of calcium chloride and ammonium thiosulfate on bermudagrass uptake of urea nitrogen  

Microsoft Academic Search

Calcium chloride (CaCl2) and ammonium thiosulfate (ATS) have demonstrated an ability to inhibit urea hydrolysis and NH3 volatilization. The objective of this experiment was to determine the effect of rainfall and soil drying on the ability of CaCl2 and ATS to increase bermudagrass nitrogen (N) uptake from surface?applied urea. Urea fertilizer, labeled with N and amended with CaCl2 or ATS,

J. J. Sloan; W. B. Anderson

1998-01-01

332

Calcium chloride and ammonium thiosulfate as ammonia volatilization inhibitors for urea fertilizers  

Microsoft Academic Search

Surface?applied urea fertilizers are susceptible to hydrolysis and loss of nitrogen (N) through ammonium (NH3) volatilization when conditions favorable for these processes exist. Calcium chloride (CaCl2) and ammonium thiosulfate (ATS) may inhibit urease activity and reduce NH3 volatilization when mixed with urea fertilizers. The objective of this study was to evaluate the effectiveness of CaCl2 and ATS as urea?N loss

J. J. Sloan; W. B. Anderson

1995-01-01

333

Fate of urea nitrogen applied to a banana crop in the wet tropics of Queensland  

Microsoft Academic Search

This paper reports a study in the wet tropics of Queensland on the fate of urea applied to a dry or wet soil surface under banana plants. The transformations of urea were followed in cylindrical microplots (10.3 cm diameter × 23 cm long), a nitrogen (N) balance was conducted in macroplots (3.85 m × 2.0 m) with 15N labelled urea,

P. Prasertsak; J. R. Freney; P. G. Saffigna; O. T. Denmead; B. G. Prove

2001-01-01

334

An experimental study of moisture uptake and transport in a bed of urea particles  

Microsoft Academic Search

Urea, a widely used nitrogen fertilizer, is susceptible to moisture adsorption from ambient air which leads to caking and\\u000a handling problems. Scanning Electron Microscopy (SEM) images of a nearly spherical urea particle and a fractured cross-sectional\\u000a area of a urea particle show internal porosity and external surface roughness. BET test analysis indicates that the internal\\u000a surface area available for water

Xiaodong Nie; Robert W. Besant; Richard W. Evitts

2008-01-01

335

Temporal and spatial dynamics of urea uptake and regeneration rates and concentrations in Chesapeake Bay  

Microsoft Academic Search

We examined the temporal and spatial variability of urea concentrations and urea uptake and regeneration rates collected on\\u000a cruises along the longitudinal axis of the Chesapeake Bay between 1972 and 1998. Interannually, mean Bay-wide surface urea\\u000a concentrations ranged between 0.49 and 0.91 ?g-at N l?1 with a nearly 50% decrease in surface concentrations observed between 1988 and 1998. Concentrations of

Michael W. Lomas; T. Mark Trice; Patricia M. Glibert; Deborah A. Bronk; James J. McCarthy

2002-01-01

336

Pretreatment with hypertonic NaCl protects MDCK cells against high urea concentrations  

Microsoft Academic Search

In antidiuresis, the cells of the renal medulla are exposed to high extracellular concentrations of NaCl and urea. Since\\u000a urea equilibrates with the intracellular compartment and is known to perturb intracellular macromolecules, high urea concentrations\\u000a may well disturb the structure and function of cell proteins. Two types of organic substances are believed to counteract the\\u000a adverse effects of high intracellular

Wolfgang Neuhofer; E. Müller; Anke Burger-Kentischer; Maria-Luisa Fraek; Klaus Thurau; F.-X. Beck

1998-01-01

337

Imprecision of the hemodialysis dose when measured directly from urea removal  

Microsoft Academic Search

Imprecision of the hemodialysis dose when measured directly from urea removal.BackgroundThe postdialysis blood urea nitrogen (BUN; Ct) is a pivotal parameter for assessing hemodialysis adequacy by conventional blood-side methods, but Ct is relatively unstable because of hemodialysis-induced disequilibrium. The uncertainty associated with this method is potentially reduced or eliminated by measuring urea removed on the dialysate side, a more direct

THOMAS A. DEPNER; TOM GREENE; FRANK A. GOTCH; JOHN T. DAUGIRDAS; PRAKASH R. KESHAVIAH; ROBERT A. STAR

1999-01-01

338

A longitudinal, five year survey of urea kinetic parameters in CAPD patients  

Microsoft Academic Search

A longitudinal, five year survey of urea kinetic parameters in CAPD patients. This study reports on the five years' evolution of the KT\\/V urea index and protein catabolic rate (PCR) in 16 CAPD patients who were treated with a constant daily dialysis dose. Total KT\\/V urea index decreased with time from a value of 0.96 ± 0.06 at the start

Norbert H Lameire; Raymond Vanholder; Denise Veyt; Marie-Christine Lambert; Severin Ringoir

1992-01-01

339

Studies on untreated and urea-treated rice straw from three cultivation seasons  

Microsoft Academic Search

Untreated and urea-treated straw and straw fractions of seven rice varieties from three cultivation seasons have been evaluated on their DM, OM loss and degradation characteristics from in sacco disappearance and in vitro gas production measurements. Drying temperatures from 45°C to 100°C did not seem to influence the degradability of urea-treated rice straw, whereas urea-treated straw dried at freezing temperatures

H. Sh Shen; F Sundstøl; D. B Ni

1998-01-01

340

EFFECTIVENESS OF AMMONIFICATION THROUGH UREA IN IMPROVING THE FEEDING VALUE OF RICE STRAW IN RUMINANTS  

Microsoft Academic Search

Eight male crossbred sheep with four in each batch were used to provide backup research for an integrated rural development project. The crude protein (CP) content of rice straw tree increased from 2.9% through various treatments with urea as follows: 3% and 5% urea in an earthen pit for 20 days, 5.9% CP and 6.7% CP respectively; 5% urea in

M Saadullah; M Haque; F Dolberg

341

On Route Aggregation IBM T. J. Watson  

E-print Network

from a set of child routes falling under a common parent prefix and advertises the single sum- mary that can derive from RA. Configuring RA on one router interface can in- fluence how routes are advertised route in lieu of announcing all the child routes. It al- lows routers to handle fewer prefixes and has

Xie, Geoffrey

342

IPR: An Integrated Placement and Routing Algorithm  

Microsoft Academic Search

In this paper, we propose to address the inconsistency between the place- ment and routing objectives by fully integrating global routing into placement. As a first attempt to this novel approach, we focus on routability issue. We call the proposed algorithm for routing congestion minimization IPR (Integrated Placement and Routing). To ensure the algorithm to be computationally efficient, efficient placement

Min Pan; Chris C. N. Chu

2007-01-01

343

Di-chlorido-dimethyl-bis-(thio-urea-?S)tin(IV).  

PubMed

The title compound, [Sn(CH3)2Cl2(CH4N2S)2], crystallizes with two half-mol-ecules in the asymmetric unit. Both mol-ecules are completed by inversion symmetry with the two Sn(IV) atoms located on inversion centers. The metal atoms have distorted octa-hedral coordination environments defined by two Cl atoms, two C atoms of methyl groups and two thio-urea S atoms. In the crystal, mol-ecules are linked via N-H?Cl and N-H?S hydrogen bonds, forming a three-dimensional structure. PMID:24764948

Sow, Yaya; Diop, Libasse; Fernandes, Manuel A; Stoeckli-Evans, Helen

2014-03-01

344

Di-chlorido-dimethyl-bis-(thio-urea-?S)tin(IV)  

PubMed Central

The title compound, [Sn(CH3)2Cl2(CH4N2S)2], crystallizes with two half-mol­ecules in the asymmetric unit. Both mol­ecules are completed by inversion symmetry with the two SnIV atoms located on inversion centers. The metal atoms have distorted octa­hedral coordination environments defined by two Cl atoms, two C atoms of methyl groups and two thio­urea S atoms. In the crystal, mol­ecules are linked via N—H?Cl and N—H?S hydrogen bonds, forming a three-dimensional structure. PMID:24764948

Sow, Yaya; Diop, Libasse; Fernandes, Manuel A.; Stoeckli-Evans, Helen

2014-01-01

345

Lattice model calculations on aqueous acetone and tetramethyl urea  

E-print Network

In frames of the Ising model, we analyze self-organization of aqueous acetone (AC) and tetramethyl urea (TMU), caused by lyotropic phase transformations. Using the lattice Monte Carlo simulations, we confirmed the statements by Koga and co-workers on the tree content dependent mixing schemes in AC and TMU and found the values of molar fractions of surfactants, corresponding to the transitions between the mesophases of these mixing schemes. So we may compare these results with another concepts on the water structures.

L. V. Elnikova

2009-05-05

346

Heterotrimeric Coiled Coils with Core Residue Urea Side Chains  

PubMed Central

We report several coiled coil heterotrimers with varying core residue buried polar groups, all with Tm values > 43° C. Introduction of new synthetic side chain structures, including some terminating in mono-substituted ureas, diversifies the pool of viable core residue candidates. A study of core charge pairings demonstrates that, unlike dimeric systems, trimeric coiled coils do not tolerate guanidine-guanidine contacts, even in the presence of a compensating carboxylate. Overall, the roster of feasible coiled coil designs is significantly expanded. PMID:19032043

Diss, Maria L.; Kennan, Alan J.

2009-01-01

347

Urea transport across urinary bladder and salt acclimation in toad (Bufo viridis).  

PubMed

The fluxes of urea across the urinary bladder of the toad Bufo viridis have been studied under conditions of acclimation to tap water or 500 mosM NaCl solution. The [14C]urea fluxes were measured simultaneously with [3H]inulin to test for nonspecific leakage. The fluxes are quite high (Ktrans = 75 x 10(-7) cm/s at 5 mmol/l urea) and are similar in either the mucosal-to-serosal or the opposite direction. "Summer" rates were five to six times higher than the "winter" rates. Antidiuretic hormone (ADH), theophylline, and forskolin increased the fluxes to variable degrees (two to five times), similar in the two acclimation conditions. Phloretin inhibited the urea fluxes by nearly 50%. 1,3-Dimethylurea and thiourea, but not acetamide, competed with the urea fluxes effectively. The fluxes of urea were not affected by the osmotic water flow, although both responded to ADH. It is concluded that urea transport across the urinary bladder of B. viridis is by facilitated diffusion through a specific pathway independent of water flux. The inhibitory effect of the structural analogues on the urea flux was affected by salt acclimation, whereas most other characteristics did not differ significantly at 5 mmol/l external urea under the two conditions of acclimation. PMID:2331031

Shpun, S; Katz, U

1990-04-01

348

Insight into the amplification by methylated urea of the anion specificity of macromolecules.  

PubMed

Methylated urea and sugar are chaotropic and kosmotropic osmolytes, respectively. In the present work, we have investigated the specific anion effect on the lower critical solution temperature (LCST) behavior of poly(N-isopropylacrylamide) (PNIPAM) in the presence of methylated urea or sugars. Differential scanning calorimetry studies revealed that tetramethylurea can adsorb onto the PNIPAM surface, but glucose is excluded from the PNIPAM surface. The specific anion effect on the LCST behavior of PNIPAM is amplified by methylated urea but not by sugars. The amplification of the anion specificity by methylated urea is attributed to an increased difference in the anion-specific polarization of hydrogen bonds, induced by the formation of PNIPAM/methylated urea complexes via hydrophobic interactions. As the number of methyl groups on the methylated urea increases, the extent of amplification of the anion specificity increases due to increasing hydrophobic interactions between the PNIPAM and methylated urea. Additionally, no amplification of the anion specificity is observed in the presence of urea because a PNIPAM/urea complex cannot be formed via hydrophobic interactions. PMID:24667999

Liu, Lvdan; Shi, Yang; Liu, Chang; Wang, Tao; Liu, Guangming; Zhang, Guangzhao

2014-04-28

349

Sensitivity to Urea Fertilization in Three Amphibian Species L. K. Belden,2  

E-print Network

(Plethodon vehicu- lum, Rhyacotriton variegatus, and Taricha granulosa). In avoidance experiments, the three for T. granulosa at these concentrations. We suggest that environmental levels of urea could

Blaustein, Andrew R.

350

Distinct cellular pathways for resistance to urea stress and hypertonic stress.  

PubMed

During antidiuresis with elevated vasopressin, urea accumulates in the renal medulla to very high concentrations, imposing considerable cellular stress. How local cells cope with urea stress is relevant to the whole kidney because the renal medulla is the major site of residence for the renal stem cells. Previous studies showed that renal cells were incapable of preconditioning in moderate urea concentrations to enhance resistance to urea stress. Instead, preconditioning in moderately high salinity (moderate hypertonicity) has been shown to promote resistance to urea stress due to the induction of the molecular chaperone heat shock protein 70 (Hsp70), which is mediated by the transcription factor tonicity-responsive enhancer binding protein (TonEBP). Here we report that cell lines derived from the kidney and fibroblasts display enhanced resistance to urea stress after pretreatment in moderate, nonstressful concentrations of urea. Using TonEBP knockdown and immunoblot analyses, we demonstrate that TonEBP and Hsp70 are dispensable for the increased resistance to urea stress. These data suggest that cells in the renal medulla are capable of overcoming urea stress by activating distinct cellular pathways. PMID:21178107

Lee, Sang Do; Choi, Soo Youn; Kwon, H Moo

2011-03-01

351

Nutrient digestibility and protein utilization by heifers and steers fed high molasses-urea diets  

E-print Network

OF NITROGEN FROM DIFFERENT FEEDS CONSUMED BY STEERS FED THREE LEVELS OF FISH MEAL. 34, Viii Table 12 Appendix Table NITROGEN BALANCE OF STEERS FED THREE LEVELS OF FISH MEAL WITH HIGH MOLASSES-UREA DIETS. . . . . . . . BLOOD UREA CONCENTRATION, RUMEN.... Blood urea concentrations are presented in Table 12. 36 TABLE 11. NITROGEN BALANCE OF STEERS FED THREE LEVELS OF I FISH MEAL WITH HIGH MOLASSES-UREA DIETS' Fish meal level, g/100. kg body weight. 80 120 180 ~Steer 2 N intake, g N output, gs...

Pina, Angel Modesto

2012-06-07

352

Degradation of urea by bacteria and algae in mass algal cultures.  

PubMed

Studies were conducted to determine the role of bacteria and algae in the degradation of urea in industrial waste waters. The microflora accompanying algae in continuous cultures on waste waters from the nitrogen fertilizers industry was found to include bacteria capable of intensive degradation of urea. Urea hydrolyzing bacteria are with time eliminated from the algal culture. This elimination can be attributed to algal metabolites which inhibit the development of sensitive bacteria. The Chlorella vulgaris strain used in the treatment of wast waters from the nitrogen fertilizers industry did not hydrolyse urea. PMID:1227254

Chróst, R J; Owczarek, J; Matusiak, K

1975-01-01

353

Combustion-gas recirculation system  

Microsoft Academic Search

A combustion-gas recirculation system has a mixing chamber with a mixing-chamber inlet and a mixing-chamber outlet. The combustion-gas recirculation system may further include a duct connected to the mixing-chamber inlet. Additionally, the combustion-gas recirculation system may include an open inlet channel with a solid outer wall. The open inlet channel may extend into the mixing chamber such that an end

Darryl Dean

2007-01-01

354

Fourth International Microgravity Combustion Workshop  

NASA Technical Reports Server (NTRS)

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

Sacksteder, Kurt R. (Compiler)

1997-01-01

355

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

356

European Route of Industrial Heritage  

NSDL National Science Digital Library

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

357

Microgravity Smoldering Combustion Takes Flight  

NASA Technical Reports Server (NTRS)

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

1996-01-01

358

Simulating the effect of exercise on urea clearance in hemodialysis.  

PubMed

A two-compartment model of urea kinetics during hemodialysis is used to predict the effect of exercise on hemodialysis dose. It is assumed that the two compartments represent tissues that are perfused by low and high blood flows (initially 1.1 L/min and 3.8 L/min). The effect of changing the distribution of flows between the compartments, emulating the effect of exercise, is simulated using the model equations for a range of dialyzer clearances. Compartmental volumes are assumed constant (33.4 L and 8.6 L for low- and high-flow compartments, respectively). The analysis identifies muscle perfusion as a rate-limiting factor during the later stages of hemodialysis and illustrates the benefit of exercise during this phase in increasing dialysis efficiency. The model suggests that the postdialysis rebound in the blood urea concentration is eliminated by increasing flow to the low-flow compartment from 1.1 L/min to 7.1 L/min and sustaining this for at least 30 min of a 150-min dialysis session, independent of the dialyzer clearance. Additional exercise will not increase the dialysis dose. Experimental studies are required to confirm the analysis. PMID:9440097

Smye, S W; Lindley, E J; Will, E J

1998-01-01

359

Nitrogen leaching from Douglas-fir forests after urea fertilization.  

PubMed

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

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

2008-01-01

360

Soybean oil-isosorbide-based waterborne polyurethane-urea dispersions.  

PubMed

A series of soybean oil-based amide diol-isosorbide waterborne polyurethane-urea (PUU) dispersions have been successfully prepared, with amounts of isosorbide ranging from 0 to 20?wt?% of the total diol content. The thermal and mechanical properties of the resulting PUU films have been characterized by dynamic mechanical analysis, differential scanning calorimetry, thermogravimetric analysis, and mechanical testing. The results reveal that the glass transition temperature is increased with increased amounts of isosorbide, and the mechanical properties are improved significantly with the incorporation of isosorbide. For example, the Young's modulus increases from 2.3 to 63?MPa and the ultimate tensile strength increases from 0.7 to 8.2?MPa when the isosorbide amount is increased from 0 to 20?wt?%. The thermal stability decreases slightly with the incorporation of isosorbide. This work provides a new way of utilizing biorenewable materials, such as isosorbide and a soybean oil-based amide diol, for the preparation of high-performance polyurethane-urea coatings. PMID:21259447

Xia, Ying; Larock, Richard C

2011-03-21

361

Voltamperometric Discrimination of Urea and Melamine Adulterated Skimmed Milk Powder  

PubMed Central

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

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

2012-01-01

362

Kinetic investigation of erucamide synthesis using fatty acid and urea.  

PubMed

Fatty acid amides like erucamide are mainly used for lubrication and as slip agent to decrease friction in polymer and plastic industry. Erucamide is normally synthesized by ammonolysis of triglycerides or fatty acids at 200 degrees C and at high pressure (345-690 kPa.). However using urea in place of ammonia the economic synthesis of erucamide is possible at atmospheric pressure at approx 190 degrees C. In present investigation, the kinetics of synthesis of erucamide by ammonolysis of erucic acid has been investigated. The optimum conditions for the synthesis of erucamide have also been determined. 1:4 molar ratio of erucic acid to urea, 190 degrees C temperature and catalyst [P2O5 with (NH4)2H PO4, {(1:1) w/w }] concentration 3% (by wt. of erucic acid) were the optimum condition for synthesis of erucamide from erucic acid and can obtain a maximum yield of 92% of pure erucamide. Some other catalysts as titanium-iso -propoxide, phosphorus pent oxide were also tried but these catalysts were not economical. PMID:18685229

Awasthi, Neeraj Praphulla; Upadhayay, Santosh K; Singh, R P

2008-01-01

363

Combustion Byproducts Recycling Consortium  

SciTech Connect

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

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

2008-08-31

364

ACO based routing for MANETs  

E-print Network

Mobile ad hoc network (MANET) is a collection of wireless mobile nodes. It dynamically forms a temporary network without using any pre existing network infrastructure or centralized administration i.e. with minimal prior planning. All nodes have routing capabilities and forward data packets to other nodes in multi-hop fashion. As the network is dynamic, the network topology continuously experiences alterations during deployment. The biggest challenge in MANETs is to find a path between communicating nodes. The considerations of the MANET environment and the nature of the mobile nodes create further complications which results in the need to develop special routing algorithms to meet these challenges. Swarm intelligence, a bio-inspired technique, which has proven to be very adaptable in other problem domains, has been applied to the MANET routing problem as it forms a good fit to the problem. In ant societies the activities of the individuals are not regulated by any explicit form of centralized control but ar...

Arif, Mohammad

2012-01-01

365

Combustion Experiment Apparatus  

NASA Technical Reports Server (NTRS)

Interior of a combustion experiment apparatus used in the 2.2-second drop tower at NASA's Glenn Research Center. This was shown to students participating in the second Dropping in a Microgravity Environment (DIME) competition held April 23-25, 2002, at NASA's Glenn Research Center. Competitors included two teams from Sycamore High School, Cincinnati, OH, and one each from Bay High School, Bay Village, OH, and COSI Academy, Columbus, OH. DIME is part of NASA's education and outreach activities. Details are on line at http://microgravity.grc.nasa.gov/DIME_2002.html.

2002-01-01

366

Lagrangian Simulation of Combustion  

SciTech Connect

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

Ahmed F. Ghoniem

2008-05-01

367

Hybrid fluidized bed combuster  

SciTech Connect

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

Kantesaria, Prabhudas P. (Windsor, CT); Matthews, Francis T. (Poquonock, CT)

1982-01-01

368

FITC-tagged macromolecule-based alginate microspheres for urea sensoring  

NASA Astrophysics Data System (ADS)

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

Joshi, Abhijeet; Chaudhari, Rashmi; Srivastava, Rohit

2014-04-01

369

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

PubMed

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

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

2014-07-01

370

Solution Combustion Synthesis Impregnated Layer Combustion Synthesis is a Novel  

E-print Network

) · Short reaction time (~ sec) · High temperature gradient (up to 106 K/s) Two modes of CS ·Heterogeneous products on combustion temperature profile Effect of gas phase product;Conventional Combustion System: Characteristics: · Exothermic nature of reaction · High temperature (2000 °C

Mukasyan, Alexander

371

Routing Algorithm Exploits Spatial Relations  

NASA Technical Reports Server (NTRS)

A recently developed routing algorithm for broadcasting in an ad hoc wireless communication network takes account of, and exploits, the spatial relationships among the locations of nodes, in addition to transmission power levels and distances between the nodes. In contrast, most prior algorithms for discovering routes through ad hoc networks rely heavily on transmission power levels and utilize limited graph-topology techniques that do not involve consideration of the aforesaid spatial relationships. The present algorithm extracts the relevant spatial-relationship information by use of a construct denoted the relative-neighborhood graph (RNG).

Okino, Clayton; Jennings, Esther

2004-01-01

372

The Ericsson problem: Route information from a central route planner  

E-print Network

. The aim of this work is to derive a measure of travel time performance depending on the number of road is a relation between number of drivers on the road, and average travel time. In section 6 we use a simpli#12;ed that must participate in a central route planning scheme such that travel time predictions improve signi#12

Hek, Geertje

373

Preliminary assessment of combustion modes for internal combustion wave rotors  

NASA Technical Reports Server (NTRS)

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

Nalim, M. Razi

1995-01-01

374

A tool for debugging internet multicast routing  

SciTech Connect

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

Agarwal, D.; Floyd, S.

1994-03-01

375

AIR EMISSIONS FROM SCRAP TIRE COMBUSTION  

EPA Science Inventory

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

376

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

PubMed

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

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

1999-01-27

377

Research on Three-dimensional modelling of railway route in railway route selection  

Microsoft Academic Search

The application of computer Three-dimensional visualization technology in railway route selection can improve the efficiency and quality of the design of railway route selection. Three-dimensional railway route modeling is the key of the route Three-dimensional visualization. The Three-dimensional modeling methods are studied deeply in the paper, according to the feature of railway route selection design. Before Three-dimensional modeling, route selection

Lingwei Liu; Yuanyou Xia; Yuanli Han

2010-01-01

378

Electric-field-based routing: a reliable framework for routing in MANETs  

Microsoft Academic Search

Constructing multipath routes in MANETs is important for providing reliable delivery, load balancing, and bandwidth aggregation. However, popular multipath routing approaches fail to produce spatially disjoint routes in a simple and cost-effective manner, and existing single-path approaches cannot be easily modified to produce multiple disjoint routes. In this paper we propose Electric-Field-Based Routing (EFR) as a reliable framework for routing

Nam T. Nguyen; An-I Andy Wang; Peter L. Reiher; Geoffrey H. Kuenning

2004-01-01

379

Coal combustion ash haulback  

SciTech Connect

Coal mining disturbs large tracts of land which must be reclaimed. Unfortunately, iron sulfides which are common in most coals and the adjacent strata weather, forming acid mine drainage (AMD) which degrades surface and ground water. Burning of coal produces combustion by products, most of which are placed in ponds or landfills. Suitable disposal areas are difficult to find and permit, especially in urban areas. This has led to ash haulback--where the waste generated during coal burning is hauled back to a mine for disposal. The potential advantages of coal combustion ash haulback are: Disposal occurs in a disturbed area (mine) rather than disturb additional land near the power plant; The same vehicles used to haul coal from the mine can be used to return the ash to the mine; Ash, if alkaline, may provide neutralization of acidic water or mine overburden commonly found at coal mines; and Low permeability ash could reduce ground water flow through the mine backfill, thus reducing leaching of acid forming constituents or metals. Placement of ash in surface mines provides an efficient, cost-effective method of disposal while at the same time contributing to reclamation of the mine. Wise natural resource management suggests a reasonable approach to disposal of coal ash is to return it to its original location--the mine.

Gray, R.E.; Gray, T.A. [GAI Consultants, Inc., Monroeville, PA (United States)

1998-12-31

380

Electrospinning of novel biodegradable poly(ester urethane)s and poly(ester urethane urea)s for soft tissue-engineering applications  

Microsoft Academic Search

The development of biomimetic highly-porous scaffolds is essential for successful tissue engineering. Segmented poly(ester\\u000a urethane)s and poly(ester urethane urea)s have been infrequently used for the fabrication of electrospun nanofibrous tissues,\\u000a which is surprising because these polymers represent a very large variety of materials with tailored properties. This study\\u000a reports the preparation of new electrospun elastomeric polyurethane scaffolds. Two novel segmented

Pablo C. Caracciolo; Vinoy Thomas; Yogesh K. Vohra; Fabián Buffa; Gustavo A. Abraham

2009-01-01

381

Biomechanical studies on aliphatic physically crosslinked poly(urethane urea) for blood contact applications.  

PubMed

Hydrophobic and physically crosslinked (virtually crosslinked through hydrogen bonding) aliphatic poly(urethane urea)s were developed and characterized for its biomechanical properties. The aging under induced-stress (bend samples) condition reveals resistance of poly(urethane urea) to environmental stress corrosion cracking (ESC) in hydrolytic media, Ringer's solution and phosphate buffered saline at 50 degrees C. The strain-induced (20% tensile strain) and aged polymer in hydrolytic enzyme medium, papain and in buffer reveals increase of elastic modulus in papain enzyme and papain buffer. The increase of elastic modulus is attributed to unidirectional reorganisation of chains under continually strained conditions. The polymer exposed in boiling alcoholic potassium hydroxide solution (accelerated hydrolytic chemical degradation) reveals no degradation. A comparative evaluation of poly(ether urethane urea)s reveals inferior properties. Poly(ether urethane urea)s polymer undergo hydrolytic degradation in boiling alcoholic potassium hydroxide solution. The candidate poly(urethane urea) HFL 18-PUU is more promising elastomer for long-term biomechanically sensitive blood contact applications such as heart valve and blood pump diaphragm of left ventricular assist device. PMID:18305906

Thomas, Vinoy; Muthu, Jayabalan

2008-07-01

382

Salt-stabilized globular protein structure in 7 M aqueous urea solution  

E-print Network

1 Salt-stabilized globular protein structure in 7 M aqueous urea solution V. Dötsch,1 G. Wider, G Hochschule- Hönggerberg, CH-8093 Zürich, Switzerland Keywords Protein folding; Urea denaturation; Salt changing the solution conditions. In this paper we describe the influence of various salts or non

Wider, Gerhard

383

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

Code of Federal Regulations, 2012 CFR

...Urea-formaldehyde resins in molded articles. Urea-formaldehyde resins...food-contact surface of molded articles intended for use in contact...2 moles of formaldehyde in water solution. (b) The resins...The finished food-contact article, when extracted...

2012-04-01

384

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

Code of Federal Regulations, 2013 CFR

...Urea-formaldehyde resins in molded articles. Urea-formaldehyde resins...food-contact surface of molded articles intended for use in contact...2 moles of formaldehyde in water solution. (b) The resins...The finished food-contact article, when extracted...

2013-04-01

385

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

...Urea-formaldehyde resins in molded articles. Urea-formaldehyde resins...food-contact surface of molded articles intended for use in contact...2 moles of formaldehyde in water solution. (b) The resins...The finished food-contact article, when extracted...

2014-04-01

386

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

Code of Federal Regulations, 2011 CFR

...Urea-formaldehyde resins in molded articles. Urea-formaldehyde resins...food-contact surface of molded articles intended for use in contact...2 moles of formaldehyde in water solution. (b) The resins...The finished food-contact article, when extracted...

2011-04-01

387

Interactions between Hydrophobic and Ionic Solutes in Aqueous Guanidinium Chloride and Urea Solutions: Lessons  

E-print Network

Received December 22, 2006; E-mail: thirum@glue.umd.edu Abstract: In order to clarify the mechanism, of urea and water around the solutes show strong hydrogen bonding between urea's carbonyl oxygen interactions either by solvating the charged residues or by engaging in hydrogen bonds with the protein

Thirumalai, Devarajan

388

Judith Beekman and Ronald L. Thune Evaluation of the Role of Ammonia and Urea  

E-print Network

. Appl. Environ. Microbiol. 75:6712 Conclusion #12;7 E. ictaluri is the only bacterium that encodes urea are actively expressed ­Aim 1. Demonstrate transcription of the E. ictaluri urea and ammonia transporters ­Aim transporters are important to E. ictaluri pathogenesis ­Aim 1. Construct isogenic mutants of the E. ictaluri

Kane, Andrew S.

389

MICROWAVE ASSISTED PREPARATION OF CYCLIC UREAS FROM DIAMINES IN THE PRESENCE OF ZNO  

EPA Science Inventory

A microwave-assisted facile method for the preparation of various ureas, cyclic ureas, and urethanes has been developed that affords nearly quantitative yield of products at 120 degrees C (150 W), 71 kPa within 10 min using ZnO as a catalyst. The enhanced selectivity in this rea...

390

Environmental, legal and social implications of ocean urea fertilization: Sulu sea example  

Microsoft Academic Search

Ocean urea fertilization is one geoengineering proposal aimed at not only reducing the atmospheric levels of carbon dioxide but also increasing fish populations in nutrient poor areas of the ocean. Theoretically ocean fertilization promises great benefits but there is also the possibility of serious environmental damage to consider. The nature of ocean urea fertilization means it is more likely to

Julia Mayo-Ramsay

2010-01-01

391

Alginate Microspheres Comprising Multilayered Assemblies of Cresol Red and Polyelectrolytes Towards an Optical Urea Biosensor  

Microsoft Academic Search

An absorbance based enzymatic sensor for the determination of urea has been described. The sensing principle of the present device is based upon the measurement (spectrophotometrically) of the pH change produced in the aqueous environment by the products of the enzyme-catalyzed hydrolysis of urea. Cresol red (CR) dye has been used in the present work to observe the change in

M. Swati; Rohit Srivastava

2008-01-01

392

Soy flour adhesive modified with urea, citric acid and boric acid  

Microsoft Academic Search

Purpose – The purpose of this paper is to investigate an adhesive prepared from soy flour (SF) modified with urea, citric acid and boric acid as an environmentally friendly product for the wood industry. Design\\/methodology\\/approach – Urea solution was prepared at 30°C and then SF was added and stirred at 30°C for 2 hours. Citric acid solution was added and

F. Li; X. P. Li; W. H. Wang

2010-01-01

393

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

NASA Technical Reports Server (NTRS)

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

Mueller, W. A. (inventor)

1978-01-01

394

Microbial hydrolysis of urea and its subsequent nitrification in East Texas lignite mine spoil  

E-print Network

source due to its high N content (47.0 %) and economical price. Since little is known about the behavior of urea in the mixed overburden mine spoils of east Texas, a two-year study was conducted to determine rates of urea hydrolysis, and its subsequent...

Waggoner, Paul James

2012-06-07

395

Bone marrow infection caused by Actinobacillus ureae in a rheumatoid arthritis patient.  

PubMed

A patient with rheumatoid arthritis is described who presented with low-grade fever for 3 months, in whom Actinobacillus ureae was cultured from bone marrow aspirate. Fever responded favourably to penicillin therapy. It is the first reported isolation of A. ureae from bone marrow. PMID:9459406

Avlami, A; Papalambrou, C; Tzivra, M; Dounis, E; Kordossis, T

1997-11-01

396

Urea recycling in muskrats (Ondatra zibethicus): a potential nitrogen-conserving tactic?  

PubMed

The rate of 14C-urea hydrolysis was determined in 32 field-acclimatized muskrats maintained on natural diets during spring, summer, fall, and winter. We hypothesized that urea recycling occurs in muskrats during all seasons and that the conservation of tissue nitrogen via this mechanism is most prevalent in fall and winter, when forage protein levels are lowest. Muskrats exhibited higher rates of urea hydrolysis and a lower serum urea nitrogen-to-creatinine ratio in fall and winter than in spring and summer. Even after correcting for seasonal differences in blood urea pool size, the adjusted rate of urea hydrolysis was 67% higher in fall and winter than in spring and summer. There was no evidence that the maintenance nitrogen requirements of muskrats fed natural vegetation were affected by seasonal changes in the amino acid composition of the diet. We suggest that increased levels of urea recycling, coupled with adaptive mechanisms for reducing nitrogen excretion and possibly conserving carbon skeletons of essential amino acids, may allow muskrats to reduce their nitrogen requirements on fall and winter diets. Our finding that 14C-urea hydrolysis occurred during all four sampling periods suggests that nitrogen derived from this source may also be critical to supporting large hindgut microbe populations that enable this rodent to exploit the appreciable fiber content of its aquatic plant diet throughout the year. PMID:9231395

Campbell, K L; MacArthur, R A

1997-01-01

397

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

Federal Register 2010, 2011, 2012, 2013

...on solid urea from the Russian Federation. The solid...this review was produced and exported by MCC EuroChem...versions of the Issues and Decision Memorandum are...on solid urea from the Russian Federation produced and exported by EuroChem...

2011-10-27

398

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

Federal Register 2010, 2011, 2012, 2013

...A-821-801] Solid Urea From the Russian Federation: Final Results of...2011-2012 AGENCY: Enforcement and Compliance (formerly Import...order on solid urea from the Russian Federation (Russia). For...Operations, Office I, Enforcement and Compliance (E&C),...

2013-11-12

399

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

Federal Register 2010, 2011, 2012, 2013

...order on solid urea from the Russian Federation (Russia). The...Department of Commerce, 14th Street and Constitution Avenue NW., Washington...Russia. See Solid Urea From the Russian Federation: Preliminary Results...is provided for convenience and customs purposes, the...

2012-10-22

400

Effect of protein intake and urea on sodium excretion during inappropriate antidiuresis in rats.  

PubMed

Administration of urea to patients with the syndrome of inappropriate antidiuresis (SIAD) is thought to ameliorate hyponatremia by both producing an osmotic diuresis and diminishing ongoing natriuresis. The present study evaluated these effects in a rat model of SIAD utilizing dilutional hyponatremia induced by continuous infusion of 1-deamino-[8-D-arginine] vasopressin. Following 48 hours of sustained hyponatremia, separate groups of rats were then refed with either: (1) 5% dextrose alone, (2) a 20% protein chow, (3) an isocaloric protein deficient (0%) chow, or (4) the isocaloric protein-deficient chow supplemented with oral urea. Our results demonstrate that rats refed a 20% protein diet significantly improved their plasma [Na+] as compared to rats refed protein deficient diets, and this improvement was accompanied by decreases in natriuresis despite an increased glomerular filtration rate and an unchanged negative free water clearance. Identical effects were observed in rats refed a protein deficient diet but supplemented with oral urea, suggesting that urea generation from catabolism of dietary protein is responsible for the effect of protein refeeding to decrease urinary sodium excretion. Both the protein and urea refed rats had significantly higher inner medullary urea contents and concentrations compared to rats refed protein-deficient diets and also to rats studied immediately before protein refeeding, supporting the hypothesis that urea and dietary protein decrease natriuresis in patients with SIAD in association with increased inner medullary urea concentrations. PMID:3336285

Verbalis, J G; Baldwin, E F; Neish, P N; Robinson, A G

1988-01-01

401

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

Microsoft Academic Search

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,

Timothy J. Muir; Jon P. Costanzo; RICHARD E. LEE JR

2010-01-01

402

The Comparative Value of Urea and Linseed Meal for Milk Production  

Microsoft Academic Search

In earlier work (5), we established the fact that for the growth of calves urea nitrogen could be successfully used for at least a partial supply of the protein nitrogen. This protein supply, from such a simple substance as urea, was made possible through the multiplication of the microorganisms of the rumen. This intervention of microorganisms and the use of

I. W. Rupel; G. Bohstedt; E. B. Hart

1943-01-01

403

Effects of Controlled Release Urea on the Yield and Nitrogen Nutrition of Flooded Rice  

Microsoft Academic Search

Nitrogen (N) loss is one of the key problems faced by rice farmers, and Nitrogen-use efficiency in rice is often poor as a result of high N loss through volatilization, leaching, and denitrification. One of the ways to improve N efficiency is by using controlled-release urea (CRU). The CRU generally outperformed granular urea fertilizer in reducing N losses, stimulating plant

J. K. Kiran; Y. M. Khanif; H. Amminuddin; A. R. Anuar

2010-01-01

404

Automated Methods for Blood Glucose and Urea with Adaptation for Simultaneous Determination  

Microsoft Academic Search

Automated blood glucose and urea nitrogen procedures have been modified for use with the Technicon 15-mm. tubular flow-cell colorimeter to take advantage of the resulting increased sensitivity and economy. Flow diagrams for these procedures as well as for the simultaneous determination of glucose and urea are presented. Re- covery and reproducibility data are given to indicate the reliability of these

Benjamin Fingerhut; Rocco Ferzola; Walton H. Marsh; Alfred B. Miller

405

Sprinklers in Combustible Concealed Spaces  

Microsoft Academic Search

NFPA 13 - Standard for the Installation of Sprinkler Systems requires that all combustible concealed spaces be protected with sprinklers, with certain exceptions. One exception is for combustible wood joist assemblies where the ceiling membrane is within 6 inches (152 mm) of the joists. Two tests were carried out to examine fire spread in such an assembly. Automatic sprinkler protection

G. D. Lougheed; J. K. Richardson

1989-01-01

406

Nanocrystalline and long cycling LiMn 2O 4 cathode material derived by a solution combustion method for lithium ion batteries  

Microsoft Academic Search

A nanostructured LiMn2O4 spinel phase is used as a cathode for 4V lithium batteries and is prepared by solution combustion synthesis using urea as a fuel. Lithium–manganese oxides have received more increasing attention in recent years as high-capacity intercalation cathodes for rechargeable lithium-ion batteries. Nanostructured electrodes have been shown to enhance the cell cyclability. For optimum synthesis, the spinel LiMn2O4

Cheng-Zhang Lu; George Ting-Kuo Fey

2006-01-01

407

CADAT multiport placement and routing  

NASA Technical Reports Server (NTRS)

CADAT multiport-in-two dimensions program (MP2D) is powerful placement and routing aid for processing double-ended cell equivalents of high-speed silicon-onsapphire (SOS) standard-cell family. Basic purpose of MP2D is to design high-density large-integrated (LSI) arrays.

1981-01-01

408

Roots/Routes: Part I  

ERIC Educational Resources Information Center

This narrative and poetic rendering acts as an articulation of a journey of many routes. It is a storying of critical research issues and events as performances of lived experience. It is a metissage of hybrid, but interrelated, themes that find cohesion through fragmentation and coalescence, severance, and regrowth. These themes are invoked by…

Swanson, Dalene M.

2009-01-01

409

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

410

CLEMSON UNIVERSITY Accessible Exterior Routes  

E-print Network

#12;Area C: Route map -Martin Hall -Long Hall -Kinard Lab -Daniel Hall -Strode Tower -Jordan Hall -Edwards Hall -Vickery (ALC) -Cooper Library #12;#12;Project Priority · High demand building Complete Cooper Library Brick Plaza Renov. Complete Sikes Hall Parking Area

Duchowski, Andrew T.

411

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

412

Dynamic Weather Routes Architecture Overview  

NASA Technical Reports Server (NTRS)

Dynamic Weather Routes Architecture Overview, presents the high level software architecture of DWR, based on the CTAS software framework and the Direct-To automation tool. The document also covers external and internal data flows, required dataset, changes to the Direct-To software for DWR, collection of software statistics, and the code structure.

Eslami, Hassan; Eshow, Michelle

2014-01-01

413

Mission Success for Combustion Science  

NASA Technical Reports Server (NTRS)

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

Weiland, Karen J.

2004-01-01

414

Adduction of amiloride hydrochloride in urea through a modified technique for the dissolution enhancement.  

PubMed

Amiloride hydrochloride is a potassium-sparing diuretic since it favors sodium excretion and potassium reabsorption. In the present study, urea, a well-known adductor for linear compounds was successfully employed for inclusion of amiloride hydrochloride-a substituted cyclic organic compound through a modified technique. Formation of urea inclusion compounds was confirmed by FTIR, DSC and XRD. The minimum amount of rapidly adductible endocyte (RAE) required for adduction of amiloride hydrochloride in urea was estimated by a modified Zimmerschied calorimetric method. Urea-AH-RAE inclusion compounds containing varying proportions of guests were prepared and their thermal behavior studied by DSC. The inclusion compounds were also found to exhibit high content uniformity and markedly improved dissolution profile as demonstrated by increased dissolution efficiency. Studies reveal the possibility of exploiting co-inclusion of the drug in urea host lattice for the dissolution enhancement. PMID:17688282

Thakral, Seema; Madan, A K

2008-03-01

415

Accuracy of Urinary Urea Nitrogen for Predicting Total Urinary Nitrogen in Thermally Injured Patients. (Reannouncement with New Availability Information).  

National Technical Information Service (NTIS)

Estimations of total urinary nitrogen from measured urinary urea nitrogen are commonly used in calculating nitrogen balance. Recently published studies suggest the urinary urea nitrogen/total urinary nitrogen relationship is in constant and total urinary ...

E. A. Milner, W. G. Cioffi, A. D. Mason, W. F. McManus, B. A. Pruitt

1993-01-01

416

Spherical combustion clouds in explosions  

NASA Astrophysics Data System (ADS)

This study explores the properties of spherical combustion clouds in explosions. Two cases are investigated: (1) detonation of a TNT charge and combustion of its detonation products with air, and (2) shock dispersion of aluminum powder and its combustion with air. The evolution of the blast wave and ensuing combustion cloud dynamics are studied via numerical simulations with our adaptive mesh refinement combustion code. The code solves the multi-phase conservation laws for a dilute heterogeneous continuum as formulated by Nigmatulin. Single-phase combustion (e.g., TNT with air) is modeled in the fast-chemistry limit. Two-phase combustion (e.g., Al powder with air) uses an induction time model based on Arrhenius fits to Boiko's shock tube data, along with an ignition temperature criterion based on fits to Gurevich's data, and an ignition probability model that accounts for multi-particle effects on cloud ignition. Equations of state are based on polynomial fits to thermodynamic calculations with the Cheetah code, assuming frozen reactants and equilibrium products. Adaptive mesh refinement is used to resolve thin reaction zones and capture the energy-bearing scales of turbulence on the computational mesh (ILES approach). Taking advantage of the symmetry of the problem, azimuthal averaging was used to extract the mean and rms fluctuations from the numerical solution, including: thermodynamic profiles, kinematic profiles, and reaction-zone profiles across the combustion cloud. Fuel consumption was limited to ˜ 60-70 %, due to the limited amount of air a spherical combustion cloud can entrain before the turbulent velocity field decays away. Turbulent kinetic energy spectra of the solution were found to have both rotational and dilatational components, due to compressibility effects. The dilatational component was typically about 1 % of the rotational component; both seemed to preserve their spectra as they decayed. Kinetic energy of the blast wave decayed due to the pressure field. Turbulent kinetic energy of the combustion cloud decayed due to enstrophy overline{? 2} and dilatation overline{? 2}.

Kuhl, A. L.; Bell, J. B.; Beckner, V. E.; Balakrishnan, K.; Aspden, A. J.

2013-05-01

417

Comparative evaluation of different methods to estimate urea distribution volume and generation rate.  

PubMed

Eight methods to estimate urea distribution volume and generation rate from blood urea samples measured in dialysis patients are reviewed. An analytical solution has been provided for a double-pool variable volume kinetic model to allow for faster and more accurate simulation and identification. The reliable parameter estimates provided by the double-pool kinetic model starting from seven samples, were assumed as references for the estimates obtained by the remaining methods. These include three kinetic models and four methods based on urea mass-balance. In particular, the estimation techniques differ in the number of compartments where urea is assumed distributed (double- and single-pool) or in the number of blood urea samples. Among the methods based on mass-balance, two techniques neglecting the weight loss or the urea generation during dialysis, were also analysed. The results obtained during hemofiltration sessions using three samples, usually available in clinical practice at the beginning and at the end of dialysis, demonstrate that a new method based on double-pool kinetics provides, on average, the most reliable estimates. Moreover, methods belonging to a single pool view and including both weight loss and urea generation during dialysis seem to underestimate by 1 divided by 2 liters the urea distribution volume. However, neglecting the weight loss or the urea generation can overcompensate this error, resulting in a significant overestimation of the distribution volume. Finally, it has been experimentally proved that the single-pool kinetic methods overestimate the urea production rate, while techniques based on mass balance provide more reliable values. PMID:7806417

Cappello, A; Grandi, F; Lamberti, C; Santoro, A

1994-06-01

418

Sodium-dependent net urea transport in rat initial inner medullary collecting ducts.  

PubMed Central

We reported that feeding rats 8% protein for 3 wk induces net urea transport and morphologic changes in initial inner medullary collecting ducts (IMCDs) which are not present in rats fed 18% protein. In this study, we measured net urea transport in microperfused initial IMCDs from rats fed 8% protein for > or = 3 wk and tested the effect of inhibiting Na+/K(+)-ATPase activity and found that adding 1 mM ouabain to the bath reversibly inhibited net urea transport from 14 +/- 3 to 6 +/- 2 pmol/mm per min (P < 0.01), and that replacing potassium (with sodium) in the bath reversibly inhibited net urea transport from 18 +/- 3 to 5 +/- 0 pmol/mm per min (P < 0.01). Replacing perfusate sodium with N-methyl-D-glucamine reversibly inhibited net urea transport from 12 +/- 2 to 0 +/- 1 pmol/mm per min (P < 0.01), whereas replacing bath sodium had no significant effect on net urea transport. Adding 10 nM vasopressin to the bath exerted no significant effect on net urea transport. Finally, we measured Na+/K(+)-ATPase activity in initial and terminal IMCDs from rats fed 18% or 8% protein and found no significant difference in either subsegment. Thus, net urea transport in initial IMCDs from rats fed 8% protein for > or = 3 wk requires sodium in the lumen, is reduced by inhibiting Na+/K(+)-ATPase, and is unchanged by vasopressin or phloretin. These results suggest that net urea transport may occur via a novel, secondary active, sodium-urea cotransporter. PMID:7929827

Isozaki, T; Lea, J P; Tumlin, J A; Sands, J M

1994-01-01

419

Urea and hypertonicity increase expression of heme oxygenase-1 in murine renal medullary cells.  

PubMed

Epithelial cells derived from the mammalian kidney medulla are responsive to urea at the levels of signal transduction and gene regulation. Hybridization of RNA harvested from control- and urea-treated murine inner medullary collecting duct (mIMCD3) cells with a cDNA expression array encoding stress-responsive genes suggested that heme oxygenase (HO)-1 mRNA was upregulated by urea. RNase protection assay confirmed this upregulation; hypertonicity also increased HO-1 mRNA expression but neither hypertonic NaCl nor urea were effective in the nonrenal 3T3 cell line. The effect on HO-1 expression appeared to be transcriptionally mediated on the basis of mRNA half-life studies and reporter gene analyses using the promoters of both human and chicken HO-1. Although urea signaling resembles that of heavy metal signaling in other contexts, the effect of urea on HO-1 transcription was independent of the cadmium response element in this promoter. Urea-inducible HO-1 expression was sensitive to antioxidants but not to scavengers of nitric oxide. Urea also upregulated HO-1 protein expression and pharmacological inhibition of HO-1 action with zinc protoporphyrin-sensitized mIMCD3 cells to the adverse effects of hypertonicity but not to urea. Coupled with the prior observation of others that HO-1 expression increases along the renal corticomedullary gradient, these data suggest that HO-1 expression may comprise an element of the adaptive response to hypertonicity and/or urea in renal epithelial cells. PMID:11592956

Tian, W; Bonkovsky, H L; Shibahara, S; Cohen, D M

2001-11-01

420

Anion Binding in Metal-Organic Frameworks Functionalized with Urea Hydrogen-Bonding Groups  

SciTech Connect

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 strengthening the intramolecular CH{hor_ellipsis}O hydrogen bonding of N-phenyl substituents to the carbonyl oxygen atom. Theoretical calculations indicate that N,N'-bis(m-pyridyl)urea (BPU) and N,N'-bis(m-cyanophenyl)urea (BCPU) should have enhanced hydrogen-bonding donor abilities toward anions and decreased tendencies to self-associate into hydrogen-bonded tapes compared to other disubstituted ureas. Accordingly, BPU and BCPU were incorporated in MOFs as linkers through coordination of various Zn, Cu, and Ag transition metal salts, including Zn(ClO{sub 4}){sub 2}, ZnSO{sub 4}, Cu(NO{sub 3}){sub 2}, Cu(CF{sub 3}SO{sub 3}){sub 2}, AgNO{sub 3}, and AgSO{sub 3}CH{sub 3}. Structural analysis by single-crystal X-ray diffraction showed that these linkers are versatile anion binders, capable of chelate hydrogen bonding to all of the oxoanions explored. Anion coordination by the urea functionalities was found to successfully compete with urea self-association in all cases except for that of charge-diffuse perchlorate.

Custelcean, Radu [ORNL; Moyer, Bruce A [ORNL; Bryantsev, Vyacheslav S. [Pacific Northwest National Laboratory (PNNL); Hay, Benjamin P. [Pacific Northwest National Laboratory (PNNL)

2006-01-01

421

Cellulose aerogels from aqueous alkali hydroxide-urea solution.  

PubMed

Highly porous and strong cellulose aerogels were prepared by gelation of cellulose from aqueous alkali hydroxide/urea solution, followed by drying with supercritical CO2. Their morphology, pore structure, and physical properties were characterized by scanning and transmission electron microscopy, X-ray diffraction, nitrogen adsorption measurements, UV/Vis spectrometry, and tensile tests. The cellulose hydrogel was composed of interconnected about 20 nm wide. By using supercritical CO2 drying, the network structure in the hydrogel was well preserved in the aerogel. The results are preliminary but demonstrate the ability of this method to give cellulose aerogels of large surface areas (400-500 m2 g(-1)) which may be useful as adsorbents, heat/sound insulators, filters, catalyst supports, or carbon aerogel precursors. PMID:18605678

Cai, Jie; Kimura, Satoshi; Wada, Masahisa; Kuga, Shigenori; Zhang, Lina

2008-01-01

422

Di-chlorido-diphenyl-bis-(thio-urea-?S)tin(IV)  

PubMed Central

The title compound, [Sn(C6H5)2Cl2(CH4N2S)2], has been obtained from the reaction between Sn(C6H5)2Cl2 and SC(NH2)2. The asymmetric unit consists of one half of the mol­ecular unit, the remainder generated by a twofold rotation axis located along the Cl—Sn—Cl bonds. The SnIV atom is coordinated by two phenyl groups, two Cl atoms and two thio­urea ligands in an all trans octa­hedral C2Cl2S2 environment. Individual mol­ecules are connected through N—H?Cl hydrogen bonds, leading to a three-dimensional network structure. Intra­molecular N—H?Cl hydrogen bonds are also present. PMID:24098172

Sow, Yaya; Diop, Libasse; Molloy, Kieran C.; Kociok-Kohn, Gabriele

2013-01-01

423

Di-chlorido-diphenyl-bis-(thio-urea-?S)tin(IV).  

PubMed

The title compound, [Sn(C6H5)2Cl2(CH4N2S)2], has been obtained from the reaction between Sn(C6H5)2Cl2 and SC(NH2)2. The asymmetric unit consists of one half of the mol-ecular unit, the remainder generated by a twofold rotation axis located along the Cl-Sn-Cl bonds. The Sn(IV) atom is coordinated by two phenyl groups, two Cl atoms and two thio-urea ligands in an all trans octa-hedral C2Cl2S2 environment. Individual mol-ecules are connected through N-H?Cl hydrogen bonds, leading to a three-dimensional network structure. Intra-molecular N-H?Cl hydrogen bonds are also present. PMID:24098172

Sow, Yaya; Diop, Libasse; Molloy, Kieran C; Kociok-Köhn, Gabriele

2013-01-01

424

Macrocyclic bis(ureas) as ligands for anion complexation  

PubMed Central

Summary Two macrocyclic bis(ureas) 1 and 2, both based on diphenylurea, have been synthesized. Compound 1 represents the smaller ring with two ethynylene groups as linkers and 2 the larger ring with two butadiynylene groups. On thermal treatment to 130 °C molecule 1 splits up into two dihydroindoloquinolinone (3) molecules. Both compounds 1 and 2 form adducts with polar molecules such as dimethyl sulfoxide (DMSO) and dimethylformamide (DMF) and act as complexing agents towards a series of anions (Cl?, Br?, I?, NO3 ?, HSO4 ?). The crystal structures of 3, 2·2DMSO, 2·2DMF, and of the complex NEt4[Br·2] have been determined. Quantitative investigations of the complexation equilibria were performed via 1H NMR titrations. While 1 is a rather weak complexing agent, the large ring of 2 binds anions with association constants up to log K = 7.93 for chloride ions. PMID:25161744

Kretschmer, Claudia; Dittmann, Gertrud

2014-01-01

425

Forced cocurrent smoldering combustion  

NASA Technical Reports Server (NTRS)

An analytical model of cocurrent smoldering combustion through a very porous solid fuel is developed. Smoldering is initiated at the top of a long radially insulated uniform fuel cylinder, so that the smolder wave propagates downward, opposing an upward-forced flow of oxidizer, with the solid fuel and the gaseous oxidizer entering the reaction zone from the same direction (hence, cocurrent). Radiative heat transfer was incorporated using a diffusion approximation, and smoldering was modeled using a one-step reaction mechanism. The results indicate that, for a given fuel, the final temperature depends only on the initial oxygen mass flux, increasing logarithmically with the mass flux. The smolder velocity is linearly dependent on the initial oxygen mass flux, and, at a fixed value of the flux, increases with initial oxygen mass fraction. The mathematical relationship determining the conditions for steady smolder propagation is presented.

Dosanjh, Sudip S.; Pagni, Patrick J.; Fernandez-Pello, A. Carlos

1987-01-01

426

Fluids and Combustion Facility-Combustion Integrated Rack  

NASA Technical Reports Server (NTRS)

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

Francisco, David R.

1998-01-01

427

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

428

Transportation Routing and Scheduling: Alternatives and Innovations.  

ERIC Educational Resources Information Center

There are two basic approaches offered in current computerized transportation routing and scheduling programs: the mathematical programming approach and the intuitive optimization approach. Lists questions that an informed buyer should ask of the routing and scheduling company. (MLF)

Dembowski, Frederick L.

1988-01-01

429

Computerized Bus Routing in San Francisco.  

ERIC Educational Resources Information Center

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

Caswell, Peter J.; Jungherr, J. Anton

1979-01-01

430

Understanding Route Redistribution Carnegie Mellon University  

E-print Network

even argue that because of a more dynamic business environment fueled by acquisitions and mergers of multiple domains or routing instances [1]. Routing instances form for many reasons. Company acquisitions

Xie, Geoffrey

431

The Price of Atomic Selfish Ring Routing?  

E-print Network

A major component of large-scale network systems is the routing mechanism, ... cations (DIMAP), University of Warwick, Coventry, CV4 7AL, United Kingdom, ... in a ring, the simplest 2-connected network, the problem of choosing routes in.

2008-05-27

432

Path-Based, Randomized, Oblivious, Minimal Routing  

E-print Network

Path-based, Randomized, Oblivious, Minimal routing (PROM) is a family of oblivious, minimal, path-diverse routing algorithms especially suitable for Network-on-Chip applications with n x n mesh geometry. Rather than choosing ...

Cho, Myong Hyon

2009-01-01

433

76 FR 19747 - Solid Urea From the Russian Federation and Ukraine: Final Results of the Expedited Sunset Reviews...  

Federal Register 2010, 2011, 2012, 2013

...A-823-801] Solid Urea From the Russian Federation and Ukraine: Final Results...orders on solid urea from the Russian Federation (Russia) and Ukraine, pursuant to section...Orders on Solid Urea From the Russian Federation and Ukraine'' from Gary...

2011-04-08

434

Relationship of whole body nitrogen utilization to urea kinetics in growing steers.  

PubMed

Urea kinetics were measured in 2 experiments, with treatments designed to change protein deposition by the animal. Our hypothesis was that increased protein deposition by cattle (Bos taurus) would reduce urea production and recycling to the gastrointestinal tract. Urea kinetics were measured by continuous intravenous infusion of (15)N(15)N-urea followed by measurement of enrichment in urinary urea at plateau. In Exp. 1, 6 steers (139 kg) were maintained in a model in which leucine was the most limiting AA. Treatments were arranged as a 2 × 3 factorial and were provided to steers in a 6 × 6 Latin square design. Leucine treatments included 0 or 4 g/d of abomasally supplemented L-leucine, and energy treatments included control, abomasal glucose infusion (382 g DM/d), or ruminal VFA infusion (150 g/d of acetic acid, 150 g/d of propionic acid, and 50 g/d of butyric acid). Leucine supplementation increased (P < 0.01) N retention, and energy supplementation tended to increase (P = 0.09) N retention without differences between glucose and VFA supplements (P = 0.86). Energy supplementation did not strikingly improve the efficiency of leucine utilization. Although both leucine and energy supplementation reduced urinary urea excretion (P ? 0.02), treatments did not affect urea production (P ? 0.34) or urea recycling to the gut (P ? 0.30). The magnitude of change in protein deposition may have been too small to significantly affect urea kinetics. In Exp. 2, 6 steers (168 kg) were maintained in a model wherein methionine was the most limiting AA. Steers were placed in 2 concurrent 3 × 3 Latin squares. Steers in one square were implanted with 24 mg of estradiol and 120 mg trenbolone acetate, and steers in the other square were not implanted. Treatments in each square were 0, 3, or 10 g/d of L-methionine. Implantation numerically improved N retention (P = 0.13) and reduced urea production rate (P = 0.03), urinary urea excretion (P < 0.01), and urea recycling to the gastrointestinal tract (P = 0.14). Effects of methionine were similar to implantation, but smaller in magnitude. When protein deposition by the body is increased markedly, ruminally available N in the diet may need to be increased to offset reductions in urea recycling. PMID:22851238

Titgemeyer, E C; Spivey, K S; Parr, S L; Brake, D W; Jones, M L

2012-10-01

435

Supplemental methionine and urea for gestating beef cows consuming low quality forage diets.  

PubMed

A study was conducted to evaluate Met requirements of late-gestation beef cows consuming low quality forages on the premise that inadequate supply of metabolizable AA may limit protein accretion during pregnancy. Five ruminally cannulated, multiparous late-gestation beef cows (490 +/- 27 kg), of predominantly Angus (> or =75%) with Hereford and Simmental breeding, were used in a 5 x 5 Latin square experiment to evaluate the effects of postruminal dl-Met supplementation on N retention, serum metabolites, and plasma AA concentrations during the third trimester of pregnancy. The basal diet was fed individually, and weights of refusals were recorded for N intake determination. Treatments consisted of no urea, urea (0.053 +/- 0.002 g/kg of BW daily), urea + 5 g of Met/d, urea + 10 g of Met/d, and urea + 15 g of Met/d. Cows were adapted to the experimental diet 30 d before the beginning of the study, with periods lasting for 14 d; 4 d to allow for clearance of the previous treatment effects, 4 d for adaptation to the treatments, and 6 d for total fecal and urine collection. Blood samples were collected every 4 h on d 13 of each period for analysis of serum metabolites and plasma AA. Inclusion of urea increased DM and OM intakes (urea vs. no urea; P = 0.05), but no further improvement in intake was observed with inclusion of Met. Serum urea concentrations increased with inclusion of urea (P = 0.03) and responded quadratically (P = 0.06) when Met was added, with the lowest concentration observed in the urea + 5 g of Met/d treatment. More N was retained with the inclusion of urea (P = 0.04), and N retention increased linearly (P = 0.07) with inclusion of Met. Plasma Met concentration increased linearly (P < 0.01) with inclusion of Met. These data suggest that Met was a limiting AA and that supplementation of a combination of urea and 5 g/d of rumen-protected Met to low quality, forage diets will improve N retention and promote protein accretion during late pregnancy. PMID:17060412

Waterman, R C; Löest, C A; Bryant, W D; Petersen, M K

2007-03-01

436

Scalable routing in delay tolerant networks  

Microsoft Academic Search

The non-existence of an end-to-end path poses a challenge in adapting the traditional routing algorithms to delay tolerant networks (DTNs). Previous works include centralized rout- ing approaches based on deterministic mobility, ferry-based routing with deterministic or semi-deterministic mobility, ?ooding-based approaches for networks with general mo- bility, and probability-based routing for semi-deterministic mobility models. Unfortunately, none of these methods can guarantee

Cong Liu; Jie Wu

2007-01-01

437

Scalable Routing in Cyclic Mobile Networks  

Microsoft Academic Search

The non-existence of an end-to-end path poses a challenge in adapting traditional routing algorithms to delay tolerant networks (DTNs). Previous works have covered centralized routing approaches based on deterministic mobility, ferry-based routing with deterministic or semi-deterministic mobility, flooding-based approaches for networks with general mobility, and probability-based routing for semi-deterministic mobility models. Unfortunately, none of these methods can guarantee both scalability

Cong Liu; Jie Wu

2009-01-01

438

Recent developments in securing Internet routing protocols  

Microsoft Academic Search

Routing protocols distribute network topology information around the routers of a network. They are part of the critical network\\u000a infrastructure, but are vulnerable to both internal and external attacks. In this paper, different routing protocols are first\\u000a introduced, followed by reviews of routing protocol security publications in academia and industry. The general vulnerabilities\\u000a and threats of routing protocols are then

L. He

2006-01-01

439

Filtration combustion: Smoldering and SHS  

NASA Technical Reports Server (NTRS)

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

Matkowsky, Bernard J.

1995-01-01

440

Microgravity combustion of dust suspensions  

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

441

Tier 1 Exceptional Talent Visa Route Introduction  

E-print Network

Tier 1 Exceptional Talent Visa Route Introduction The points based system is the entry route for researchers to use are Tiers 1 (Exceptional talent), 2 (General) and 5 (Government Authorised Exchange of Tier 1 Exceptional Talent Visa route The Royal Society, British Academy or Royal Academy of Engineering

Berzins, M.

442

45 CFR 1310.20 - Trip routing.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 false Trip routing. 1310.20 Section 1310.20 Public...Special Requirements § 1310.20 Trip routing. (a) Each agency providing transportation...the following basic principles of trip routing are adhered to: (1) The...

2010-10-01

443

Making CDN and ISP Routings Symbiotic  

Microsoft Academic Search

Internet Service Providers (ISPs) route traffic at the IP layer with the preference of less inter-carrier payments while Content Distribution Networks (CDNs) route traffic at the application layer with the preference of better application performance. Such mismatch of routing preferences leads to conflicts that eventually result in higher operational cost for both ISPs and CDNs. In this paper, we propose

Varun Khare; Beichuan Zhang

2011-01-01

444

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

445

Performance Analysis of Adhoc Network Routing Protocols  

Microsoft Academic Search

Routing in adhoc networks is nontrivial due to highly dynamic nature of the nodes. In recent years several routing protocols targeted at mobile adhoc networks are being proposed and prominent among them are DSDV, AODV, TORA, and DSR. This paper does the comprehensive performance analysis of the routing protocols using ns2 simulator considering all the metrics as suggested by RFC

P. Chenna Reddy; P. ChandraSekhar Reddy

2006-01-01

446

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

447

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

448

Routing strategy based on traffic correlation parameter  

NASA Astrophysics Data System (ADS)

One of the most immediate benefits of MPLS is the ability to perform traffic engineering. Traditionally, the only mechanism for redirecting traffic has been to change the link metrics in the Interior Gateway Protocol (IGP, responsible for routing within a site), but this can potentially change the paths of all the packets traversing that link. With MPLS there is a finer granularity because it does not operate on a link basis and therefore it is possible to shift individual LSPs from congested paths to an alternate path. This also simplifies the operation of the network operator since the network operator can assign global optimization algorithms that provide mapping from the traffic demand to the physical link that could not be done using local optimization. Constraint-based routing (or its variant Explicit Routing ER) allows for traffic engineering. What is important, however, is that ER can allow for distributed routing of the same type as the routing and wavelength assignment in the optical adaptation layer. Furthermore, constraint-based routing use topology/resources updates to perform distributed LSP route computations, which can be used to deploy distributed shortest-path lightpath routing. A detailed comparison between distributed path routing strategies based on traffic parameters and fix path routing schemes is presented in this paper and it is shown that a distributed path routing scheme based on traffic correlation parameter is superior than fix path routing schemes.

Marciano, Lorenzo; Castanon, Gerardo A.

2004-09-01

449

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

450

76 FR 766 - Amtrak Emergency Routing Orders  

Federal Register 2010, 2011, 2012, 2013

...a designated e-mail address for this...Amtrak emergency routing order applications...filing an emergency routing order application...via facsimile, e-mail, or in person...filing an emergency routing order application...via facsimile, e-mail, or in...

2011-01-06

451

A general greedy channel routing algorithm  

Microsoft Academic Search

A general approach for the channel routing problem is presented as a framework for a class of heuristic routing algorithms. The algorithm is shown to possess a backtracking capability that increases the chance of completing the routing with a minimum number of tracks. Since the concepts described are general, they can be applied to other channel problems, such as switchbox

Tai-tsung Ho; S. Sitharama Iyengar; Si-qing Zheng

1991-01-01

452

Source Routing Made Practical in Embedded Networks  

Microsoft Academic Search

Reducing packet latency is an important requirement in embedded networks. Source routing can be used to reduce processing delay at intermediate nodes and thereby reduce the overall packet latency. However source routing is not scalable which makes it unsuitable for larger networks. The addition of the source route to every packet reduces the system good put (application level throughput). Further,

Arijit Ghosh; Tony Givargis

2009-01-01

453

Routing Around Decoys Max Schuchard1  

E-print Network

, University of California, Berkeley ABSTRACT Decoy Routing is a new approach to Internet censorship circum routing aims to ham- per nation-state level Internet censorship by having routers, rather than end hosts, BGP, Telex, Cirripede, Censorship 1. INTRODUCTION Decoy routing [19, 27, 18], as exemplified by Telex

Minnesota, University of

454

Wavelength Routing Networks -1 Optical Networks  

E-print Network

Wavelength Routing Networks - 1 Optical Networks: from fiber transmission to photonic switching Wavelength-Routing Networks Fabio Neri and Marco Mellia TLC Networks Group ­ Electronics Department e.mellia@polito.it ­ tel. 011 564 4173 #12;Wavelength Routing Networks - 3 Course program outline · Introduction

Mellia, Marco

455

Combustion at reduced gravitational conditions  

NASA Technical Reports Server (NTRS)

The theoretical structures needed for the predictive analyses and interpretations for flame propagation and extinction for clouds of porous particulates are presented. Related combustion theories of significance to reduced gravitational studies of combustible media are presented. Nonadiabatic boundaries are required for both autoignition theory and for extinction theory. Processes that were considered include, pyrolysis and vaporization of particulates, heterogeneous and homogeneous chemical kinetics, molecular transport of heat and mass, radiative coupling of the medium to its environment, and radiative coupling among particles and volume elements of the combustible medium.

Berlad, A. L.; Wang, L. S.; Joshi, N.; Pai, C. I.

1980-01-01

456

Combustion-gas recirculation system  

DOEpatents

A combustion-gas recirculation system has a mixing chamber with a mixing-chamber inlet and a mixing-chamber outlet. The combustion-gas recirculation system may further include a duct connected to the mixing-chamber inlet. Additionally, the combustion-gas recirculation system may include an open inlet channel with a solid outer wall. The open inlet channel may extend into the mixing chamber such that an end of the open inlet channel is disposed between the mixing-chamber inlet and the mixing-chamber outlet. Furthermore, air within the open inlet channel may be at a pressure near or below atmospheric pressure.

Baldwin, Darryl Dean (Lacon, IL)

2007-10-09

457

International Space Station -- Combustion Rack  

NASA Technical Reports Server (NTRS)

The combustion chamber for the Combustion Integrated Rack section of the Fluids and Combustion Facility (FCF) is shown extracted for servicing and with the optical bench rotated 90 degrees for access to the rear elements. The FCF will be installed, in phases, in the Destiny, the U.S. Laboratory Module of the International Space Station (ISS), and will accommodate multiple users for a range of investigations. This is an engineering mockup; the flight hardware is subject to change as designs are refined. The FCF is being developed by the Microgravity Science Division (MSD) at the NASA Glenn Research Center. (Photo credit: NASA/Marshall Space Flight Center)

2000-01-01

458

International Space Station -- Combustion Rack  

NASA Technical Reports Server (NTRS)

The combustion chamber for the Combustion Integrated Rack section of the Fluids and Combustion Facility (FCF) is shown extracted for servicing. The FCF will be installed, in phases, in the Destiny, the U.S. Laboratory Module of the International Space Station (ISS), and will accommodate multiple users for a range of investigations. This is an engineering mockup; the flight hardware is subject to change as designs are refined. The FCF is being developed by the Microgravity Science Division (MSD) at the NASA Glenn Research Center. (Photo credit: NASA/Marshall Space Flight Center)

2000-01-01

459

International Space Station -- Combustion Rack  

NASA Technical Reports Server (NTRS)

The combustion chamber for the Combustion Integrated Rack section of the Fluids and Combustion Facility (FCF) is shown in its operational configuration. The FCF will be installed, in phases, in the Destiny, the U.S. Laboratory Module of the International Space Station (ISS), and will accommodate multiple users for a range of investigations. This is an engineering mockup; the flight hardware is subject to change as designs are refined. The FCF is being developed by the Microgravity Science Division (MSD) at the NASA Glenn Research Center. (Photo credit: NASA/Marshall Space Flight Center)

2000-01-01

460

International Space Station - Combustion Rack  

NASA Technical Reports Server (NTRS)

The combustion chamber for the Combustion Integrated Rack section of the Fluids and Combustion Facility (FCF) is shown opened for installation of burn specimens. The FCF will be installed, in phases, in the Destiny, the U.S. Laboratory Module of the International Space Station (ISS), and will accommodate multiple users for a range of investigations. This is an engineering mockup; the flight hardware is subject to change as designs are refined. The FCF is being developed by the Microgravity Science Division (MSD) at the NASA Glenn Research Center. (Photo credit: NASA/Marshall Space Flight Center)

2000-01-01

461

General gate array routing using a k-terminal net routing algorithm with failure prediction  

Microsoft Academic Search

In this paper a general approach to gate array routing is presented, based on an abstract routing space model. An efficient k-terminal net maze runner is described. It does not partition nets into 2-terminal net routing problems, but solves the problem by simultaneously growing k search waves. It is shown that the explored routing space diminishes when compar ed to

Ed P. Huijbregts; Jochen A. G. Jess

1993-01-01

462

New Flooding Control Schemes Applied In Route Initialisation For The Ad Hoc On Demand Routing Protocols  

E-print Network

New Flooding Control Schemes Applied In Route Initialisation For The Ad Hoc On Demand Routing College London * Email: uceephu@ucl.ac.uk Abstract: This paper introduces a new route request flooding. This scheme aims to control and reduce the route request flooding. Furthermore, the scheme combines

Haddadi, Hamed

463

What Is the Best Route? Route-Finding Strategies of Middle School Students Using GIS  

ERIC Educational Resources Information Center

This paper summarizes a research project conducted to investigate the strategies developed by middle school students to solve a route-finding problem using Arc View GIS software. Three different types of route-finding strategies were identified. Some students were visual route-finders and used a highly visual strategy; others were logical route…

Wigglesivorth, John C.

2003-01-01

464

Effective heat of combustion for flaming combustion of conifers  

Microsoft Academic Search

The heat of combustion of burning trees is often used in forest-fire hazard modeling to relate mass-loss results to the heat produced; therefore reliable values are needed. Experimental results for the effective heat of combustion of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) trees are presented as a function of moisture content. It is also shown that during a forest fire, the

Vytenis Babrauskas

2006-01-01

465

Structural characteristics that stabilize or destabilize different assembly levels of phycocyanin by urea.  

PubMed

Phycocyanin is one of the two phycobiliproteins always found in the Phycobilisome antenna complex. It is always situated at the ends of the peripheral rods, adjacent to the core cylinders composed of allophycocyanin. The basic phycocyanin monomer is an (??) dimer of globin-like subunits with three covalently linked phycocyanobilin cofactors. Monomers assemble further into trimers, hexamers, and rods which include non-pigmented linker proteins. Upon isolation in low ionic strength solution, rods quickly disintegrate into phycocyanin trimers, which lose contacts with other phycobiliproteins and with the linker proteins. The trimers, however, are quite stable and only the presence of high concentrations of chaotropic agents (such as urea), very acidic solutions, or elevated temperatures induces monomerization, followed by separation between the subunits. We have recently determined the crystal structures of phycocyanin from the thremophilic cyanobacterium Thermosynechococcus vulcanus in the presence of 2 or 4 M urea, and shown that 4 M urea monomerizes the phycocyanin trimers. In this paper, we will describe the phycocyanin structures in 2 and 4 M urea more completely. By mapping out the urea positions, we describe the structural elements within the trimeric interaction interface that may be interrupted by the presence of 4 M urea. In addition, we also identify what are the structural characteristics that prevent 4 M urea from inducing subunit dissociation. PMID:24687534

Marx, Ailie; Adir, Noam

2014-07-01

466

Catalytic hydrolysis of urea from wastewater using different aluminas by a fixed bed reactor.  

PubMed

In order to find an effective method for treating urea wastewater, the experiments on the hydrolysis of urea in wastewater were conducted in a fixed bed reactor with different aluminas (?-Al2O3, ?-Al2O3, and ?-Al2O3) as catalysts respectively in contrast with inert ceramic particle. The results indicate that the three alumina catalysts show obvious catalytic activity for urea hydrolysis at 125 °C. The order of activity is ?-Al2O3?>??-Al2O3?>??-Al2O3, and the activity difference increases with increasing temperature. According to the characterization results, surface acidity has little impact on the activity of catalyst. However, it was found that surface basicity of alumina catalyst plays an important role in catalytic hydrolysis of urea, and the activity of catalyst may be also influenced by the basic strength. With ?-Al2O3 as catalyst, the urea concentration in wastewater is reduced to 4.96 mg/L at a temperature of 165 °C. Moreover, the ?-Al2O3 shows a good stability for urea hydrolysis. The hydrolysis of urea over ?-Al2O3 catalyst can evidently reduce the reaction temperature and is promising to replace industrial thermal hydrolysis process. PMID:24952253

Shen, Shuguang; Li, Meina; Li, Binbin; Zhao, Zhijun

2014-11-01

467

The structural basis of urea-induced protein unfolding in ?-catenin.  

PubMed

Although urea and guanidine hydrochloride are commonly used to denature proteins, the molecular underpinnings of this process have remained unclear for a century. To address this question, crystal structures of ?-catenin were determined at various urea concentrations. These structures contained at least 105 unique positions that were occupied by urea molecules, each of which interacted with the protein primarily via hydrogen bonds. Hydrogen-bond competition experiments showed that the denaturing effects of urea were neutralized when polyethylene glycol was added to the solution. These data suggest that urea primarily causes proteins to unfold by competing and disrupting hydrogen bonds in proteins. Moreover, circular-dichroism spectra and nuclear magnetic resonance (NMR) analysis revealed that a similar mechanism caused protein denaturation in the absence of urea at pH levels greater than 12. Taken together, the results led to the conclusion that the disruption of hydrogen bonds is a general mechanism of unfolding induced by urea, high pH and potentially other denaturing agents such as guanidine hydrochloride. Traditionally, the disruption of hydrophobic interactions instead of hydrogen bonds has been thought to be the most important cause of protein denaturation. PMID:25372676

Wang, Chao; Chen, Zhongzhou; Hong, Xia; Ning, Fangkun; Liu, Haolin; Zang, Jianye; Yan, Xiaoxue; Kemp, Jennifer; Musselman, Catherine A; Kutateladze, Tatinna G; Zhao, Rui; Jiang, Chengyu; Zhang, Gongyi

2014-11-01

468

Adaptive network based on fuzzy inference system for equilibrated urea concentration prediction.  

PubMed

Post-dialysis urea rebound (PDUR) has been attributed mostly to redistribution of urea from different compartments, which is determined by variations in regional blood flows and transcellular urea mass transfer coefficients. PDUR occurs after 30-90min of short or standard hemodialysis (HD) sessions and after 60min in long 8-h HD sessions, which is inconvenient. This paper presents adaptive network based on fuzzy inference system (ANFIS) for predicting intradialytic (Cint) and post-dialysis urea concentrations (Cpost) in order to predict the equilibrated (Ceq) urea concentrations without any blood sampling from dialysis patients. The accuracy of the developed system was prospectively compared with other traditional methods for predicting equilibrated urea (Ceq), post dialysis urea rebound (PDUR) and equilibrated dialysis dose (eKt/V). This comparison is done based on root mean squares error (RMSE), normalized mean square error (NRMSE), and mean absolute percentage error (MAPE). The ANFIS predictor for Ceq achieved mean RMSE values of 0.3654 and 0.4920 for training and testing, respectively. The statistical analysis demonstrated that there is no statistically significant difference found between the predicted and the measured values. The percentage of MAE and RMSE for testing phase is 0.63% and 0.96%, respectively. PMID:23806679

Azar, Ahmad Taher

2013-09-01

469

Urea Monitor Based on Chemiluminescence and Electrolysis as a Marker for Dialysis Efficiency  

NASA Astrophysics Data System (ADS)

We have developed a practical urea monitor based on a chemiluminescent (CL) reaction of urea and hypobromous acid produced by electrolysis of sodium bromide (NaBr) for measuring urea concentration in spent dialysate at set intervals. A reagent containing 4×10-2 M hypobromous acid is produced by electrolysis of an electrolyte containing 5.9 M NaBr and 0.2 M sodium hydroxide (NaOH). Chemiluminescence is emitted by injection of spent hemodialysis fluid (0.11 ml) into the reagent, and the CL-intensity is measured by a photomultiplier tube using the photon counting technique. The CL-intensity is proportional to the 0.9th power of the urea concentration between 7×10-4 and 2×10-2 M. The urea monitor can determine the urea concentration in spent dialysate samples collected from the waste line of a dialyzer, and the time for the intermittent measurements including the cleaning cycle of the reaction chamber is 3 min. The urea concentrations measured by the monitor are in close agreement with those measured by the conventional enzyme colorimetric method using urease for the spent dialysate collected during a hemodialysis treatment, and the correlation coefficient is 0.93.

Ozaki, Masahiro; Okabayashi, Tohru; Ishimaru, Teppei; Hayashi, Kunihito; Hori, Jun'ya; Yamamoto, Isao; Nakagawa, Masuo

470

Safety assessment of diammonium phosphate and urea used in the manufacture of cigarettes.  

PubMed

A tiered testing strategy has been employed to evaluate the potential for new ingredients, tobacco processes, and technological developments to alter the mainstream smoke or biological activity that results from burning cigarette tobacco. The foundation of this evaluation strategy is comparative testing, typically including chemical and biological assessments. In the manufacture of cigarettes, diammonium phosphate (DAP) and urea have been historically used as ingredients added to tobacco, to reconstituted tobacco sheet, and to other processed tobaccos. As part of ongoing stewardship efforts, a toxicological assessment of cigarettes with and without DAP and urea was conducted. Chemical and biological analyses were conducted for test cigarettes added 0.5% DAP and 0.2% urea in the final blend and also for those added 1.0% DAP and 0.41% urea in the final blend compared to reference cigarettes without added DAP or urea. Principal components of this evaluation included a determination of selected mainstream smoke constituent yields, an Ames assay in Salmonella typhimurium strains TA98 and TA100, a sister chromatid exchange assay in Chinese hamster ovary cells, a 13-week inhalation study of mainstream cigarette smoke in Sprague-Dawley rats, and a 30-week dermal tumor-promotion evaluation of mainstream cigarette smoke condensate in SENCAR mice. Comparative evaluations demonstrated that the addition of DAP and urea to cigarettes at up to 1% and 0.41%, respectively, does not alter the biological activity compared to reference cigarettes without DAP or urea. PMID:18272354

Stavanja, Mari S; Curtin, Geoffrey M; Ayres, Paul H; Bombick, Elizabeth R; Borgerding, Michael F; Morgan, Walter T; Garner, Charles D; Pence, Deborah H; Swauger, James E

2008-04-01

471

Simple chiral urea gelators, (R)- and (S)-2-heptylurea: their gelling ability enhanced by chirality.  

PubMed

We present the first report on the synthesis of chiral ureas, (R)- and (S)-2-heptylurea, and their gelling behaviors. The ureas were prepared by the reactions of chiral amines and phenyl carbamate in the presence of triethylamine. On cooling from homogeneous solutions, the chiral ureas form gels in water and various nonpolar organic solvents, such as cyclohexane, toluene, and tetrachloromethane, while the racemate gelatinize only toluene and tetrachloromethane among the solvents we examined. The gelling ability of the enantiomeric urea is higher than the racemate, as the critical gelling concentrations in toluene, for example, were 0.2% and 0.7% (wt/wt), respectively. The enhanced gelling ability of the enantiomeric ureas is due to the 1D supramolecular structure formed during gelation. In contrast, the racemate crystallizes into two-dimensional lamellae, where the (R)- and (S)-2-heptylurea exist alternatingly in a plane (P2(1)/c space group). Powder X-ray diffraction pattern of the enantiomeric urea showed that it has a different crystal lattice from that of the racemate, implying that the steric effect by the methyl group at the chiral center prevents the pure enantiomers from having 2D hydrogen bonding networks, which lead to sheet-like structures for the racemate and the achiral analog. Thus the pure enantiomers self-organize into one-dimensional fibrous structures. The simplicity and the ambidextrous gelling behaviors of the chiral ureas in forming both hydrogels and organogels present numerous possibilities for future applications. PMID:21396655

Kim, Jong-Uk; Schollmeyer, Dieter; Brehmer, Martin; Zentel, Rudolf

2011-05-15

472

Multicast Routing of Hierarchical Data  

NASA Technical Reports Server (NTRS)

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

Shacham, Nachum

1992-01-01

473

Daisy Found on 'Route 66'  

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

474

Integrating DTN and MANET routing  

Microsoft Academic Search

Mobile Ad-hoc Network (MANET) routing protocols aim at establishing end-to-end paths between communicating nodes and thus support end-to-end semantics of existing transports and applications. In contrast, DTN-based communication schemes imply asynchronous communication (and thus often require new applications) but achieve better reachability, particularly in sparsely populated environments. In this paper, we suggest a hybrid scheme that combines AODV and DTN-based

Jörg Ott; Dirk Kutscher; Christoph Dwertmann

2006-01-01

475

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

476

Kompetenscentrum Frbrnningsprocesser Centre of Competence Combustion Processes  

E-print Network

of Competence Combustion Processes Faculty of Engineering, LTH P.O. Box 118 SE-221 00 Lund Sweden #12;KCFP July 1, 1995. The main goal of this centre is to better understand the combustion process in internal combustion engines.Of particular interest are the combustion processes with low enough temperature

477

Overfeed fixed-bed combustion of wood  

Microsoft Academic Search

Research on the combustion of wood on a fixed grate with a separate supply of combustion air is described in this paper. From the layer of the wood on the grate, only fixed carbon was burned in the primary combustion chamber in the presence of primary air, whereas the volatiles were burned subsequently in the secondary combustion chamber in the

Janez Oman; Matija Tuma

1999-01-01

478

Steady\\/unsteady gas turbine combustion simulator  

Microsoft Academic Search

A conceptual gas turbine combustion simulator is proposed to study steady and unsteady combustion phenomena at conditions relevant to aviation engines. It is intended to duplicate the flow and combustion characteristics of an aviation engine in a simple laboratory scale device in order to conduct scientific study to provide deeper insight to the complex combustion dynamics problems and other related

Pratikash Prakash Panda

2011-01-01

479

Radiation heat transfer in combustion systems  

Microsoft Academic Search

An adequate treatment of thermal radiation heat transfer is essential to a mathematical model of the combustion process or to a design of a combustion system. This paper reviews the fundamentals of radiation heat transfer and some recent progress in its modeling in combustion systems. Topics covered include radiative properties of combustion products and their modeling and methods of solving

R. Viskanta; M. P. Menguc

1987-01-01

480

Charge-signal multiplication mediated by urea wires inside Y-shaped carbon nanotubes  

NASA Astrophysics Data System (ADS)

In previous studies, we reported molecular dynamics (MD) simulations showing that single-file water wires confined inside Y-shaped single-walled carbon nanotubes (Y-SWNTs) held strong and robust capability to convert and multiply charge signals [Y. S. Tu, P. Xiu, R. Z. Wan, J. Hu, R. H. Zhou, and H. P. Fang, Proc. Natl. Acad. Sci. U.S.A. 106, 18120 (2009); Y. Tu, H. Lu, Y. Zhang, T. Huynh, and R. Zhou, J. Chem. Phys. 138, 015104 (2013)]. It is fascinating to see whether the signal multiplication can be realized by other kinds of polar molecules with larger dipole moments (which make the experimental realization easier). In this article, we use MD simulations to study the urea-mediated signal conversion and multiplication with Y-SWNTs. We observe that when a Y-SWNT with an external charge of magnitude 1.0 e (the model of a signal at the single-electron level) is solvated in 1 M urea solutions, urea can induce drying of the Y-SWNT and fill its interiors in single-file, forming Y-shaped urea wires. The external charge can effectively control the dipole orientation of the urea wire inside the main channel (i.e., the signal can be readily converted), and this signal can further be multiplied into 2 (or more) output signals by modulating dipole orientations of urea wires in bifurcated branch channels of the Y-SWNT. This remarkable signal transduction capability arises from the strong dipole-induced ordering of urea wires under extreme confinement. We also discuss the advantage of urea as compared with water in the signal multiplication, as well as the robustness and biological implications of our findings. This study provides the possibility for multiplying signals by using urea molecules (or other polar organic molecules) with Y-shaped nanochannels and might also help understand the mechanism behind signal conduction in both physical and biological systems.

Lv, Mei; He, Bing; Liu, Zengrong; Xiu, Peng; Tu, Yusong

2014-07-01

481

Effects of urea on the microstructure and phase behavior of aqueous solutions of polyoxyethylene surfactants  

PubMed Central

Membrane proteins are made soluble in aqueous buffers by the addition of various surfactants (detergents) to form so-called protein-detergent complexes (PDCs). Properties of membrane proteins are commonly assessed by unfolding the protein in the presence of surfactant in a buffer solution by adding urea. The stability of the protein under these conditions is then monitored by biophysical methods such as fluorescence or circular dichroism spectroscopy. Often overlooked in these experiments is the effect of urea on the phase behavior and micellar microstructure of the different surfactants used to form the PDCs. Here the effect of urea on five polyoxyethylene surfactants – n-octylytetraoxyethylene (C8E4), n-octylpentaoxyethylene (C8E5), n-decylhexaoxyethylene (C10E6), n-dodecylhexaoxyethylene (C12E6) and n-dodecyloctaoxylethylene (C12E8) – is explored. The presence of urea increases the critical micelle concentration (CMC) of all surfactants studied, indicating that the concentration of both the surfactant and urea should be considered in membrane protein folding studies. The cloud point temperature of all surfactants studied also increases with increasing urea concentration. Small-angle neutron scattering shows a urea-induced transition from an elongated to a globular shape for micelles of C8E4 and C12E6. In contrast, C8E5 and C12E8 form more globular micelles at room temperature and the micelles remain globular as the urea concentration is increased. The effects of increasing urea concentration on micelle structure are analogous to those of decreasing the temperature. The large changes in micelle structure observed here could also affect membrane protein unfolding studies by changing the structure of the PDC. PMID:21359094

Bianco, Carolina L.; Schneider, Craig S.; Santonicola, Mariagabriella; Lenhoff, Abraham M.; Kaler, Eric W.

2010-01-01

482

Urea unfolding of peptide helices as a model for interpreting protein unfolding.  

PubMed

To provide a model system for understanding how the unfolding of protein alpha-helices by urea contributes to protein denaturation, urea unfolding was measured for a homologous series of helical peptides with the repeating sequence Ala-Glu-Ala-Ala-Lys-Ala and chain lengths varying from 14 to 50 residues. The dependence of the helix propagation parameter of the Zimm-Bragg model for helix-coil transition theory (s) on urea molarity ([urea]) was determined at 0 degree C with data for the entire set of peptides, and a linear dependence of In s on [urea] was found. The results were fitted by the binding-site model and by the solvent-exchange model for the interaction of urea with the peptides. Each of these thermodynamic models is able to describe the data quite well and we are not able to discern any difference between the ability of each model to fit the data. Thus a linear relation, ln s = ln s0 - (m/RT).[urea], fits the data for alpha-helix unfolding, just as others have found for protein unfolding. When the m value determined here for alpha-helix unfolding is multiplied by the number of helical residues in partly helical protein molecules, the resulting values agree within a factor of 2 with observed m values for these proteins. This result indicates that the interaction between urea and peptide groups accounts for a major part of the denaturing action of urea on proteins, as predicted earlier by some model studies with small molecules. PMID:7816813

Scholtz, J M; Barrick, D; York, E J; Stewart, J M; Baldwin, R L

1995-01-01

483

Optimization of OSPF Routing in IP Networks  

NASA Astrophysics Data System (ADS)

The Internet is a huge world-wide packet switching network comprised of more than 13,000 distinct subnetworks, referred to as Autonomous Systems (ASs) autonomous system AS . They all rely on the Internet Protocol (IP) internet protocol IP for transport of packets across the network. And most of them use shortest path routing protocols shortest path routing!protocols , such as OSPF or IS-IS, to control the routing of IP packets routing!of IP packets within an AS. The idea of the routing is extremely simple — every packet is forwarded on IP links along the shortest route between its source and destination nodes of the AS. The AS network administrator can manage the routing of packets in the AS by supplying the so-called administrative weights of IP links, which specify the link lengths that are used by the routing protocols for their shortest path computations. The main advantage of the shortest path routing policy is its simplicity, allowing for little administrative overhead. From the network engineering perspective, however, shortest path routing can pose problems in achieving satisfactory traffic handling efficiency. As all routing paths depend on the same routing metric routing!metric , it is not possible to configure the routing paths for the communication demands between different pairs of nodes explicitly or individually; the routing can be controlled only indirectly and only as a whole by modifying the routing metric. Thus, one of the main tasks when planning such networks is to find administrative link weights that induce a globally efficient traffic routing traffic!routing configuration of an AS. It turns out that this task leads to very difficult mathematical optimization problems. In this chapter, we discuss and describe exact integer programming models and solution approaches as well as practically efficient smart heuristics for such shortest path routing problems shortest path routing!problems .

Bley, Andreas; Fortz, Bernard; Gourdin, Eric; Holmberg, Kaj; Klopfenstein, Olivier; Pióro, Micha?; Tomaszewski, Artur; Ümit, Hakan