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1

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

SciTech Connect

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

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

2012-03-15

2

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

PubMed

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

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

2014-01-01

3

New synthetic route of polyoxometalate-based hybrids in choline chloride\\/urea eutectic media  

Microsoft Academic Search

The deep eutectic solvents synthetic method was initially explored as a facile synthesis route to prepare new polyoxometalate (POM)-based hybrids. Such a method can not only avoid poor solubility, lower yields and the potential explosion, but also act as a new type of noxious, convenient and environmental friendly organic reagents. Using the choline chloride\\/urea eutectic mixture as the deep eutectic

Shi-Ming Wang; Yun-Wu Li; Xiao-Jia Feng; Yang-Guang Li; En-Bo Wang

2010-01-01

4

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

Microsoft Academic Search

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

Khandoker Abul Hossain; Mohammad Nazri Mohd. Jaafar

5

Oxide-ion conductivity of calcia- and yttria-stabilized zirconias prepared by a rapid-combustion route  

Microsoft Academic Search

Calcia- and yttria-stabilized zirconias have been synthesised by a novel rapid-combustion route. The oxide-ion conductivities of these stabilized zirconias are comparable to these of commercially prepared samples. Variations in grain boundary impedance of calcia- and yttria-stabilized zirconias with composition and temperature are presented.

A. K. Shukla; Vandana Sharma; N. Arul Dhas; K. C. Patil

1996-01-01

6

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

7

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

PubMed

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

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

2014-10-15

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

Routing  

Microsoft Academic Search

Desirable features of routing protocols for Mobile Ad Hoc Networks (MANETs) include ability to adapt to changing network conditions due to mobility and provide quality control mechanisms during the life time of a route. Current routing protocols that provide Quality of service (QoS) for MANETs have proposed routing based on a single QoS metric. This paper proposes a QoS aware

Sirisha R. Medidi; Knut-Helge Vik

10

Isotopic and molecular fractionation in combustion; three routes to molecular marker validation, including direct molecular 'dating' (GC/AMS)  

NASA Astrophysics Data System (ADS)

The identification of unique isotopic, elemental, and molecular markers for sources of combustion aerosol has growing practical importance because of the potential effects of fine particle aerosol on health, visibility and global climate. It is urgent, therefore, that substantial efforts be directed toward the validation of assumptions involving the use of such tracers for source apportionment. We describe here three independent routes toward carbonaceous aerosol molecular marker identification and validation: (1) tracer regression and multivariate statistical techniques applied to field measurements of mixed source, carbonaceous aerosols; (2) a new development in aerosol 14C metrology: direct, pure compound accelerator mass spectrometry (AMS) by off-line GC/AMS ('molecular dating'); and (3) direct observation of isotopic and molecular source emissions during controlled laboratory combustion of specific fuels. Findings from the combined studies include: independent support for benzo( ghi)perylene as a motor vehicle tracer from the first (statistical) and second (direct 'dating') studies; a new indication, from the third (controlled combustion) study, of a relation between 13C isotopic fractionation and PAH molecular fractionation, also linked with fuel and stage of combustion; and quantitative data showing the influence of both fuel type and combustion conditions on the yields of such species as elemental carbon and PAH, reinforcing the importance of exercising caution when applying presumed conservative elemental or organic tracers to fossil or biomass burning field data as in the first study.

Currie, L. A.; Klouda, G. A.; Benner, B. A.; Garrity, K.; Eglinton, T. I.

11

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

SciTech Connect

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

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

1995-12-31

12

Synthesis of barium hexaferrite nano-particles via mechano-combustion route  

Microsoft Academic Search

Nano-size particles of barium hexaferrite have been synthesized by what is termed mechano-combustion after milling of intermediate products obtained in the sol–gel combustion process using nitrate–citrate gels prepared from metal nitrates and citric acid. The effects of precursor milling conditions on the phase evolution, crystallite size and annealing behavior of the products were investigated using XRD technique.The XRD results indicate

A. Ataie; S. E. Zojaji

2007-01-01

13

Correlation between structural and electrical properties of Mg 1?2 x Zn x Ni x Al 2O 4 ( x = 0.0–0.5) ceramic nanomaterials synthesized by a urea assisted microwave combustion method  

Microsoft Academic Search

A urea assisted microwave combustion method was used to synthesize Mg1?2xNixZnxAl2O4 (x=0.0–0.5) ceramic materials. X-ray diffraction (XRD) analysis confirmed the formation of a single spinel phase with an average Scherrer crystallite size of in the range 24–51nm. The chemical composition of the synthesized compounds was determined by energy dispersive X-ray fluorescence (ED-XRF). The synthesized materials show crystalline morphology as evidenced

Muhammad Javed Iqbal; Bushra Ismail

2010-01-01

14

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

15

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

16

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.

2014-01-28

17

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

E-print Network

The use of urea (NH2CONH2) to remove nitric oxide (NO) from exhaust streams was investigated using a laboratory laminar-flow reactor. The experiments used a number of gas compositions to simulate different combustion exhaust gases. The urea...

Park, Yong Hun

2004-09-30

18

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

NASA Astrophysics Data System (ADS)

YAlO3:Ho3+ (1-5 mol%) nanophosphors have been prepared by solution combustion route using oxalyl dihydrazide (ODH) as a fuel. The final product was well characterized by powder X-ray diffraction (PXRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), UV-Vis, etc. PXRD patterns confirm the formation of highly crystalline orthorhombic phase structure. SEM and TEM studies show the particles are dumbbell shape, highly agglomerated and nano-size (?30 nm). The direct energy band gap (Eg) values estimated from Tauc's relation were found to be in the range 5.76-5.99 eV. Photoluminescence (PL) studies show green (540 and 548 nm) and red (645 and 742 nm) emissions upon excited at 452 nm wavelength. The emission peaks at ?742 and 645 nm was associated with the transitions of 5F4 ? 5I7 and 5F5 ? 5I8 respectively. The higher energy bands located at 540 and 548 nm were associated with 5F4, 5S2 ? 5I8 transitions. Thermoluminescence (TL) studies of ?-irradiated YAlO3:Ho3+ (1-5 mol%) show two glow peaks at 223 and 325 °C recorded at a heating rate of 2.5 °C s-1. The 223 °C glow peak follow linear behavior up to 1 kGy and after that, it showed sub-linearity. Up to 1 kGy, the phosphor is quite useful in radiation dosimetry. The kinetic parameters (E, b and s) were estimated from glow peak shape method. The CIE coordinate values lies within the green region. Therefore, the present phosphors may have potential application in WLEDs as green phosphor.

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

2013-11-01

19

Disposition of exogenous urea and effects of diet in rats.  

PubMed

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

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

2006-01-01

20

Controlling the composition, microstructure, electrical and magnetic properties of LiFe5O8 powders synthesized by sol gel auto-combustion method using urea as a fuel  

NASA Astrophysics Data System (ADS)

Nanocrystalline lithium ferrite LiFe5O8 powders were synthesized by the sol gel auto-combustion method from the corresponding metal nitrates using urea as a fuel. DTA results showed that the LiFe5O8 phase started to form at temperature around 385 °C. X-ray diffraction analysis indicates that all compositions were formed in a single-phase cubic spinel structure at different annealing temperatures from 400 to 800 °C for 2 h. The lattice parameter was found to decrease whereas the particle size was increased with annealing temperature. The frequency exponent "s" of lithium ferrite lies in the range 0.5?s?1, which confirmed the electron hopping between Fe2+ and Fe3+ ions. The electron mobility in LiFe5O8 samples ranged from 0.05 to 0.29 eV, which clearly indicated that the present lithium ferrites have semiconductor-like behavior. The saturation magnetization was increased on increasing the annealing temperature up to 800 °C. High saturation magnetization (Ms=51.9 emu/g) was achieved for the ferrite powders produced at annealing temperature 800 °C for 2 h.

Rashad, M. M.; El-Shaarawy, M. G.; Shash, N. M.; Maklad, M. H.; Afifi, F. A.

2015-01-01

21

A new solution combustion route to synthesize LiCoO 2 and LiMn 2O 4  

Microsoft Academic Search

Commercially important, high-voltage, lithium cathodes, such as LiCoO2 and LiMn2O4 have been synthesized from nitrates, following the ‘soft-chemistry’ approach using starch as the combustion-assisting component. The minimum temperature required for phase formation and the degree of crystallinity has been evaluated from thermal studies and X-ray diffraction analysis, respectively. The starch-assisted combustion (SAC) method produces mono-dispersed powders of grain size below

P. Kalyani; N. Kalaiselvi; N. Muniyandi

2002-01-01

22

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...

23

Urea for hyponatremia?  

PubMed

Once the standard of care for cerebral edema, urea can also be used to treat hyponatremia. The 2014 European Clinical Practice Guidelines recommend urea for the treatment of the syndrome of inappropriate antidiuretic hormone, while discouraging use of vasopressin antagonists. Although there is evidence that urea can diminish hypertonic injury to brain cells caused by rapid correction of hyponatremia, clinical trials are needed that include patients at high risk to develop complications from overcorrection. PMID:25635717

Sterns, Richard H; Silver, Stephen M; Hix, John K

2015-02-01

24

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

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

25

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

26

Molecular evolution of urea amidolyase and urea carboxylase in fungi  

PubMed Central

Background Urea amidolyase breaks down urea into ammonia and carbon dioxide in a two-step process, while another enzyme, urease, does this in a one step-process. Urea amidolyase has been found only in some fungal species among eukaryotes. It contains two major domains: the amidase and urea carboxylase domains. A shorter form of urea amidolyase is known as urea carboxylase and has no amidase domain. Eukaryotic urea carboxylase has been found only in several fungal species and green algae. In order to elucidate the evolutionary origin of urea amidolyase and urea carboxylase, we studied the distribution of urea amidolyase, urea carboxylase, as well as other proteins including urease, across kingdoms. Results Among the 64 fungal species we examined, only those in two Ascomycota classes (Sordariomycetes and Saccharomycetes) had the urea amidolyase sequences. Urea carboxylase was found in many but not all of the species in the phylum Basidiomycota and in the subphylum Pezizomycotina (phylum Ascomycota). It was completely absent from the class Saccharomycetes (phylum Ascomycota; subphylum Saccharomycotina). Four Sordariomycetes species we examined had both the urea carboxylase and the urea amidolyase sequences. Phylogenetic analysis showed that these two enzymes appeared to have gone through independent evolution since their bacterial origin. The amidase domain and the urea carboxylase domain sequences from fungal urea amidolyases clustered strongly together with the amidase and urea carboxylase sequences, respectively, from a small number of beta- and gammaproteobacteria. On the other hand, fungal urea carboxylase proteins clustered together with another copy of urea carboxylases distributed broadly among bacteria. The urease proteins were found in all the fungal species examined except for those of the subphylum Saccharomycotina. Conclusions We conclude that the urea amidolyase genes currently found only in fungi are the results of a horizontal gene transfer event from beta-, gamma-, or related species of proteobacteria. The event took place before the divergence of the subphyla Pezizomycotina and Saccharomycotina but after the divergence of the subphylum Taphrinomycotina. Urea carboxylase genes currently found in fungi and other limited organisms were also likely derived from another ancestral gene in bacteria. Our study presented another important example showing plastic and opportunistic genome evolution in bacteria and fungi and their evolutionary interplay. PMID:21447149

2011-01-01

27

Evidence for urea cycle activity in Sporosarcina ureae  

Microsoft Academic Search

Sporosarcina ureae BS 860, a motile, sporeforming coccus, possesses the enzymes required for a functioning urea (ornithine) cycle. This is only the second known example of urea cycle activity in a prokaryote. Specific activities are reported for ornithine carbamoyltransferase, argininosuccinase, arginase, and urease. Although argininosuccinate synthetase activity could not be detected directly in crude cell extracts, indirect evidence from radiocarbon

Stephen E. Gruninger; Manuel Goldman

1988-01-01

28

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

29

MANAGING UREA-CONTAINING FERTILIZERS  

E-print Network

-- 83 Urea 16 122 UAN solution (28%) 12 125 Ammonium nitrate 2 132 Oberle & Bundy, 1988. Data from one, Lancaster, WI N source Ammonia loss (%) Yield (tons/acre) None -- 0.74 Urea 19 1.09 Ammonium nitrate 1 1 1993 1994 1995 ----------- bu/acre --------- Ammonium nitrate 118 a 177 a 163 a UAN spray 94 bc 140 b

Balser, Teri C.

30

Phylogenetic Status of Sporosarcina ureae  

Microsoft Academic Search

The taxonomic position of Sporosarcina ureae has been historically controversial: in the seventh edition of Bergey's Manual (21, it is as- signed to the genus Sarcina in the family Mi- crococcaceae, whereas in the most recent edi- tion it is placed in the family Bacillaceae (3). The controversy originates from the fact that the vegetative cells of S. ureae resemble

KENNETH J. PECHMAN; BOBBY J. LEWIS; CARL R. WOESE

31

Urea biosensor for hemodialysis monitoring  

Microsoft Academic Search

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

1999-01-01

32

Urea biosensor for hemodialysis monitoring  

Microsoft Academic Search

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

Robert S

1999-01-01

33

What Is a Urea Cycle Disorder?  

MedlinePLUS

... urea cycle. These enzymes are responsible for removing ammonia from the blood stream. The urea cycle involves ... disorders, the nitrogen accumulates in the form of ammonia, a highly toxic substance, resulting in hyperammonemia (elevated ...

34

Molecular Structure of Urea nitrate  

NSDL National Science Digital Library

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

2002-09-23

35

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

36

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

37

Expression of urea transporters and their regulation.  

PubMed

UT-A and UT-B families of urea transporters consist of multiple isoforms that are subject to regulation of both acutely and by long-term measures. This chapter provides a brief overview of the expression of the urea transporter forms and their locations in the kidney. Rapid regulation of UT-A1 results from the combination of phosphorylation and membrane accumulation. Phosphorylation of UT-A1 has been linked to vasopressin and hyperosmolality, although through different kinases. Other acute influences on urea transporter activity are ubiquitination and glycosylation, both of which influence the membrane association of the urea transporter, again through different mechanisms. Long-term regulation of urea transport is most closely associated with the environment that the kidney experiences. Low-protein diets may influence the amount of urea transporter available. Conditions of osmotic diuresis, where urea concentrations are low, will prompt an increase in urea transporter abundance. Although adrenal steroids affect urea transporter abundance, conflicting reports make conclusions tenuous. Urea transporters are upregulated when P2Y2 purinergic receptors are decreased, suggesting a role for these receptors in UT regulation. Hypercalcemia and hypokalemia both cause urine concentration deficiencies. Urea transporter abundances are reduced in aging animals and animals with angiotensin-converting enzyme deficiencies. This chapter will provide information about both rapid and long-term regulation of urea transporters and provide an introduction into the literature. PMID:25298340

Klein, Janet D

2014-01-01

38

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

39

40 CFR 721.9892 - Alkylated urea.  

Code of Federal Regulations, 2011 CFR

...2011-07-01 2011-07-01 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...

2011-07-01

40

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

41

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

PubMed Central

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

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

2013-01-01

42

Characterization of urease from Sporosarcina ureae  

Microsoft Academic Search

Alkaline stable (pH 7.75–12.5) urease from Sporosarcina ureae was purified over 400-fold by ion exchange and hydrophobic interaction chromatography. The cytoplasmic enzyme was remarkably\\u000a active with a specific activity of greater than 9300 ?mol urea degraded min-1 mg protein-1 at pH 7.5, where it has optimal activity. Although S. ureae is closely related to Bacillus pasteurii, known to posses a

Deborah D. McCoy; Aysegul Cetin; Robert P. Hausinger

1992-01-01

43

Simultaneous measurement of diazolidinyl urea, urea, and allantoin in cosmetic samples by hydrophilic interaction chromatography  

Microsoft Academic Search

A new HPLC method for simultaneous measurement of diazolidinyl urea (DU), urea, and allantoin by hydrophilic interaction chromatography using a column packed with triazol-bonded silica particles is described. The calibration curves of DU, urea, and allantoin were linear over the ranges 2.5–125.0, 30–1250, and 0.25–18.75mg\\/L, respectively. The recoveries of DU, urea, and allantoin from homemade cosmetic samples ranged from 92.84%

Takahiro Doi; Keiji Kajimura; Satoshi Takatori; Naoki Fukui; Shuzo Taguchi; Shozo Iwagami

2009-01-01

44

MECHANISMS OF UREA TOLERANCE IN UREA-ADAPTED POPULATIONS OF DROSOPHILA MELANOGASTER  

Microsoft Academic Search

When behavioral avoidance cannot prevent an animal from being exposed to novel environmental toxins, physiological mechanisms must cope with the toxin and its effects. We are investigating the basis of urea tolerance in populations of Drosophila melanogaster that have been selected to survive and develop in food containing 300 mmol l-1 urea. Previous research has demonstrated that the urea-selected larvae

REGINE ETIENNE; KECHENER FORTUNAT; VALERIE PIERCE

45

Urea in rainwater and atmospheric aerosol  

NASA Astrophysics Data System (ADS)

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

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

46

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

47

40 CFR 721.9925 - Aminoethylethylene urea methacrylamide.  

Code of Federal Regulations, 2011 CFR

...2011-07-01 false Aminoethylethylene urea methacrylamide. 721.9925 Section...Substances § 721.9925 Aminoethylethylene urea methacrylamide. (a) Chemical substance...identified generically as an aminoethylethylene urea methacrylamide (PMN...

2011-07-01

48

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

49

Deoxyribonucleic acid base composition of Sporosarcina ureae  

Microsoft Academic Search

The guanine + cytosine (GC) content of the DNAs of 11 cultures of Sporosarcina ureae and one culture of Bacillus pasteurii was determined using the methods of Marmur and Doty (1962), Frédéricqet al. (1961), and paper chromatography. The GC content in DNA of Sporosarcina ureae ranges from 39.3 to 44%. Bacillus pasteurii contained 40.4% GC in DNA. Our results support

J. Bohá?ek; M. Kocur; T. Martinec

1968-01-01

50

Urea transport through composite polyallylamine membranes  

NASA Technical Reports Server (NTRS)

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

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

1977-01-01

51

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

52

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

53

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

54

Comparative transport efficiencies of urea analogues through urea transporter UT-B.  

PubMed

Expression of urea transporter UT-B confers high urea permeability to mammalian erythrocytes. Erythrocyte membranes also permeate various urea analogues, suggesting common transport pathways for urea and structurally similar solutes. In this study, we examined UT-B-facilitated passage of urea analogues and other neutral small solutes by comparing transport properties of wildtype to UT-B-deficient mouse erythrocytes. Stopped-flow light-scattering measurements indicated high UT-B permeability to urea and chemical analogues formamide, acetamide, methylurea, methylformamide, ammonium carbamate, and acrylamide, each with P(s)>5.0 x 10(-6) cm/s at 10 degrees C. UT-B genetic knockout and phloretin treatment of wildtype erythrocytes similarly reduced urea analogue permeabilities. Strong temperature dependencies of formamide, acetamide, acrylamide and butyramide transport across UT-B-null membranes (E(a)>10 kcal/mol) suggested efficient diffusion of these amides across lipid bilayers. Urea analogues dimethylurea, acryalmide, methylurea, thiourea and methylformamide inhibited UT-B-mediated urea transport by >60% in the absence of transmembrane analogue gradients, supporting a pore-blocking mechanism of UT-B inhibition. Differential transport efficiencies of urea and its analogues through UT-B provide insight into chemical interactions between neutral solutes and the UT-B pore. PMID:17506977

Zhao, Dan; Sonawane, N D; Levin, Marc H; Yang, Baoxue

2007-07-01

55

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

56

Coulometric titration of urea with electrogenerated hypobromite.  

PubMed

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

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

2013-01-01

57

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

PubMed Central

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

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

1994-01-01

58

Mural Routes  

NSDL National Science Digital Library

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

59

Bubble Combustion  

NASA Technical Reports Server (NTRS)

A method of energy production that is capable of low pollutant emissions is fundamental to one of the four pillars of NASA s Aeronautics Blueprint: Revolutionary Vehicles. Bubble combustion, a new engine technology currently being developed at Glenn Research Center promises to provide low emissions combustion in support of NASA s vision under the Emissions Element because it generates power, while minimizing the production of carbon dioxide (CO2) and nitrous oxides (NOx), both known to be Greenhouse gases. and allows the use of alternative fuels such as corn oil, low-grade fuels, and even used motor oil. Bubble combustion is analogous to the inverse of spray combustion: the difference between bubble and spray combustion is that spray combustion is spraying a liquid in to a gas to form droplets, whereas bubble combustion involves injecting a gas into a liquid to form gaseous bubbles. In bubble combustion, the process for the ignition of the bubbles takes place on a time scale of less than a nanosecond and begins with acoustic waves perturbing each bubble. This perturbation causes the local pressure to drop below the vapor pressure of the liquid thus producing cavitation in which the bubble diameter grows, and upon reversal of the oscillating pressure field, the bubble then collapses rapidly with the aid of the high surface tension forces acting on the wall of the bubble. The rapid and violent collapse causes the temperatures inside the bubbles to soar as a result of adiabatic heating. As the temperatures rise, the gaseous contents of the bubble ignite with the bubble itself serving as its own combustion chamber. After ignition, this is the time in the bubble s life cycle where power is generated, and CO2, and NOx among other species, are produced. However, the pollutants CO2 and NOx are absorbed into the surrounding liquid. The importance of bubble combustion is that it generates power using a simple and compact device. We conducted a parametric study using CAVCHEM, a computational model developed at Glenn, that simulates the cavitational collapse of a single bubble in a liquid (water) and the subsequent combustion of the gaseous contents inside the bubble. The model solves the time-dependent, compressible Navier-Stokes equations in one-dimension with finite-rate chemical kinetics using the CHEMKIN package. Specifically, parameters such as frequency, pressure, bubble radius, and the equivalence ratio were varied while examining their effect on the maximum temperature, radius, and chemical species. These studies indicate that the radius of the bubble is perhaps the most critical parameter governing bubble combustion dynamics and its efficiency. Based on the results of the parametric studies, we plan on conducting experiments to study the effect of ultrasonic perturbations on the bubble generation process with respect to the bubble radius and size distribution.

Corrigan, Jackie

2004-01-01

60

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

61

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

62

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

63

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

Microsoft Academic Search

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

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

64

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

PubMed Central

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

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

2013-01-01

65

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

SciTech Connect

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

Cirio, A.; Boivin, R. (Ecole Nationale Veterinaire de Lyon, Marcy l'Etoile (France))

1990-05-01

66

Urea synthesis in enterocytes of developing pigs.  

PubMed Central

Urea synthesis from ammonia, glutamine and arginine was determined in enterocytes from newborn (0-day-old), 2-21-day-old suckling, and 29-58-day-old post-weaning pigs. Pigs were weaned at 21 days of age. Cells were incubated for 30 min at 37 degrees C in Krebs-Henseleit bicarbonate buffer (pH 7.4) containing (i) 0.5-2 mM NH4Cl plus 0.05-2 mM ornithine and 2 mM aspartate, (ii) 1-5 mM glutamine, or (iii) 0.5-2 mM arginine. In enterocytes from newborn and suckling pigs, there was no measurable synthesis of urea from ammonia, glutamine or arginine, and analysis of amino acids by a sensitive fluorimetric HPLC method revealed the formation of negligible amounts of ornithine from arginine. In contrast, in cells from post-weaning pigs, relatively large amounts of urea and ornithine were produced from ammonia, glutamine and arginine in a dose-dependent manner. To elucidate the mechanism of the developmental change of urea synthesis in pig enterocytes, the activities of urea-cycle enzymes were determined. The activities of enterocyte carbamoyl phosphate synthase I and ornithine carbamoyltransferase were lower in post-weaning pigs than in suckling ones, whereas there was no difference in arginino-succinate lyase. The activities of argininosuccinate synthase and arginase were increased by 4-fold and 50-100-fold, respectively, in enterocytes from post-weaning pigs compared with suckling pigs. The induction of arginase appears to be sufficient to account for the formation of urea from ammonia, glutamine and arginine in post-weaning pig enterocytes. These results demonstrate for the first time the presence of synthesis of urea from extracellular or intramitochondrially generated ammonia in enterocytes of post-weaning pigs. This hitherto unrecognized urea synthesis in these cells may be a first line of defence against the potential toxicity of ammonia produced by the extensive intestinal degradation of glutamine (a major fuel for enterocytes) and derived from diet and luminal micro-organisms. PMID:8554511

Wu, G

1995-01-01

67

21 CFR 862.1770 - Urea nitrogen test system.  

Code of Federal Regulations, 2014 CFR

...Identification. A urea nitrogen test system is a device intended to measure urea nitrogen (an end-product of nitrogen metabolism) in whole blood, serum, plasma, and urine. Measurements obtained by this device are used in the diagnosis and...

2014-04-01

68

21 CFR 862.1770 - Urea nitrogen test system.  

Code of Federal Regulations, 2013 CFR

...Identification. A urea nitrogen test system is a device intended to measure urea nitrogen (an end-product of nitrogen metabolism) in whole blood, serum, plasma, and urine. Measurements obtained by this device are used in the diagnosis and...

2013-04-01

69

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

PubMed

In plants, urea derives either from root uptake or protein degradation. Although large quantities of urea are released during senescence, urea is mainly seen as a short-lived nitrogen (N) catabolite serving urease-mediated hydrolysis to ammonium. Here, we investigated the roles of DUR3 and of urea in N remobilization. During natural leaf senescence urea concentrations and DUR3 transcript levels showed a parallel increase with senescence markers like ORE1 in a plant age- and leaf age-dependent manner. Deletion of DUR3 decreased urea accumulation in leaves, whereas the fraction of urea lost to the leaf apoplast was enhanced. Under natural and N deficiency-induced senescence DUR3 promoter activity was highest in the vasculature, but was also found in surrounding bundle sheath and mesophyll cells. An analysis of petiole exudates from wild-type leaves revealed that N from urea accounted for >13% of amino acid N. Urea export from senescent leaves further increased in ureG-2 deletion mutants lacking urease activity. In the dur3 ureG double insertion line the absence of DUR3 reduced urea export from leaf petioles. These results indicate that urea can serve as an early metabolic marker for leaf senescence, and that DUR3-mediated urea retrieval contributes to the retranslocation of N from urea during leaf senescence. PMID:25440717

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

2015-02-01

70

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

71

Characterization of urease from Sporosarcina ureae.  

PubMed

Alkaline stable (pH 7.75-12.5) urease from Sporosarcina ureae was purified over 400-fold by ion exchange and hydrophobic interaction chromatography. The cytoplasmic enzyme was remarkably active with a specific activity of greater than 9300 mumol urea degraded min-1 mg protein-1 at pH 7.5, where it has optimal activity. Although S. ureae is closely related to Bacillus pasteurii, known to possess a homopolymeric urease containing 1 nickel per subunit [M(r) = 65000], the S. ureae enzyme is comprised of three subunits [apparent M(r) = 63,100 (alpha), 14,500 (beta), and 8500 (gamma)] in an estimated alpha beta gamma 2 stoichiometry and contains 2.1 +/- 0.6 nickel ions per alpha beta gamma 2 unit as measured by atomic absorption spectrometry. Stationary phase cultures sometimes possessed low levels of urease activity, but the specific activity of cell extracts of partially purified urease preparations from such cultures could be elevated by heat treatment, dilution, or dialysis to values comparable to those observed in samples from exponentially grown cells. PMID:1510567

McCoy, D D; Cetin, A; Hausinger, R P

1992-01-01

72

Mathematics of combustion  

Microsoft Academic Search

The applications of numerical techniques to the study of combustion processes is considered. The basic equations governing combustion processes are introduced, and some novel approaches to combustion reaction modelling are described. Among the specific applications discussed are: the Burger and Korteweg-de Vries equations of detonation processes; turbulent combustion modelling; and analysis of finite amplitude waves in combustible gases.

J. D. Buckmaster; H. Rabitz; F. A. Williams; W. Fickett; J. F. Clarke

1985-01-01

73

Combustion pressure sensor  

Microsoft Academic Search

A combustion pressure sensor is described for mounting on an internal combustion engine so as to have access to the interior of a combustion cylinder. The sensor consists of: a first diaphragm means adjacent a combustion region for deflecting as a function of the magnitude of adjacent pressure in the combustion region, and for acting as a gas tight seal

Bettman

1986-01-01

74

76 FR 15339 - Solid Urea From Russia and Ukraine  

Federal Register 2010, 2011, 2012, 2013, 2014

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

2011-03-21

75

76 FR 77015 - Solid Urea From Russia and Ukraine  

Federal Register 2010, 2011, 2012, 2013, 2014

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

2011-12-09

76

75 FR 74746 - Solid Urea From Russia and Ukraine  

Federal Register 2010, 2011, 2012, 2013, 2014

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

2010-12-01

77

21 CFR 176.320 - Sodium nitrate-urea complex.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 2009-04-01 true Sodium nitrate-urea complex. 176.320 Section 176.320 Food...and Paperboard § 176.320 Sodium nitrate-urea complex. Sodium nitrate-urea complex may be safely used as a component...

2010-04-01

78

Investigating the Hydrogen-Bonding Model of Urea Denaturation  

E-print Network

Investigating the Hydrogen-Bonding Model of Urea Denaturation Laura B. Sagle, Yanjie Zhang@mail.chem.tamu.edu Abstract: The direct binding mechanism for urea-based denaturation of proteins was tested-induced denaturation of proteins. Introduction Although urea was first shown to denature proteins in 1900

79

21 CFR 176.320 - Sodium nitrate-urea complex.  

Code of Federal Regulations, 2011 CFR

...2011-04-01 2011-04-01 false Sodium nitrate-urea complex. 176.320 Section 176.320 Food...and Paperboard § 176.320 Sodium nitrate-urea complex. Sodium nitrate-urea complex may be safely used as a component...

2011-04-01

80

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. ...

81

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

Microsoft Academic Search

This study investigated the reactivity of chlorine with urea which is the main nitrogen contaminant introduced into swimming pool water by bathers. In the first part of this study, analyses showed that the mean concentrations of urea and TOC determined from 50 samples of municipal swimming pool were equal to 18.0 ?M (s.d. 11.7) and 3.5 mg C L?1 (s.d. 1.6), respectively. The mean

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

2011-01-01

82

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

Microsoft Academic Search

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

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

1996-01-01

83

American Routes  

NSDL National Science Digital Library

From Acadian folksongs to the sea songs of the coastal Carolinas, the American Routes radio program brings together all of the fine American musical traditions in one delightful two-hour block each and every week. The program is hosted by Nick Spitzer, and it has received sponsorship from Tulane University and the National Endowment for the Humanities. Some of the guests who have appeared on the program include Abbey Lincoln, Elvis Costello, Tom Waits, and Dave Brubeck. First-time visitors to the site can sign up for their email updates or just jump right in by listening to the current edition of the show. The archive dates back to 1999, and visitors can listen to the complete shows, if they wish to do so. Additionally, visitors can also use the Facebook or Twitter links offered here.

84

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

Microsoft Academic Search

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

Jian Luo; Zhaohuang Lian; Xiaolong Yan

1993-01-01

85

Combustion Control  

E-print Network

casing of the fuel control regulator with the combustion air piping. The upstream pressure on the burner air orifice is applied to the main diaphragm of the pressure balanced regulator. Assuming sufficient gas pressure at the regulator inlet..., the outlet gas pressure will equal the air impulse pressLre. As the primary control drive moves to open or close the air valve, the outlet pressure will "track" changes in air pressure. The burner is an orifice for the air (assuming that it is in good...

Riccardi, R. C.

1984-01-01

86

Routing without routes: the backpressure collection protocol  

Microsoft Academic Search

Current data collection protocols for wireless sensor networks are mostly based on quasi-static minimum-cost routing trees. We consider an alternative, highly-agile approach called backpressure routing, in which routing and forwarding decisions are made on a per-packet basis. Although there is a considerable theoretical literature on backpressure routing, it has not been implemented on practical systems to date due to concerns

Scott Moeller; Avinash Sridharan; Bhaskar Krishnamachari; Omprakash Gnawali

2010-01-01

87

Urea-induced denaturation of PreQ1-riboswitch  

E-print Network

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

Jeseong Yoon; D. Thirumalai; Changbong Hyeon

2013-07-20

88

Small-Molecule Inhibitors of Urea Transporters  

PubMed Central

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

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

2015-01-01

89

Genes and proteins of urea transporters.  

PubMed

A urea transporter protein in the kidney was first proposed in 1987. The first urea transporter cDNA was cloned in 1993. The SLC14a urea transporter family contains two major subgroups: SLC14a1, the UT-B urea transporter originally isolated from erythrocytes; and SLC14a2, the UT-A group originally isolated from kidney inner medulla. Slc14a1, the human UT-B gene, arises from a single locus located on chromosome 18q12.1-q21.1, which is located close to Slc14a2. Slc14a1 includes 11 exons, with the coding region extending from exon 4 to exon 11, and is approximately 30 kb in length. The Slc14a2 gene is a very large gene with 24 exons, is approximately 300 kb in length, and encodes 6 different isoforms. Slc14a2 contains two promoter elements: promoter I is located in the typical position, upstream of exon 1, and drives the transcription of UT-A1, UT-A1b, UT-A3, UT-A3b, and UT-A4; while promoter II is located within intron 12 and drives the transcription of UT-A2 and UT-A2b. UT-A1 and UT-A3 are located in the inner medullary collecting duct, UT-A2 in the thin descending limb and liver, UT-A5 in testis, UT-A6 in colon, UT-B1 primarily in descending vasa recta and erythrocytes, and UT-B2 in rumen. PMID:25298338

Sands, Jeff M; Blount, Mitsi A

2014-01-01

90

Ammonium and urea removal by Spirulina platensis  

Microsoft Academic Search

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

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

2006-01-01

91

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

92

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

93

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

94

The electrophoresis of transferrins in urea/polyacrylamide gels.  

PubMed Central

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

Evans, R W; Williams, J

1980-01-01

95

14C-urea breath test in C pylori gastritis  

Microsoft Academic Search

14C-urea breath test was used to detect Campylobacter pylori colonisation in 129 consecutive non-ulcer dyspepsia patients. Fasting patients were given 3 microCi (110 kBq) of 14C-labelled urea after a test meal. Breath samples were collected at 10 minute intervals for 90 minutes and the C-14 activity was counted on a liquid scintillation analyser. Urea derived 14CO2 appears in the exhaled

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

1989-01-01

96

Daily rhythm of salivary and serum urea concentration in sheep  

PubMed Central

Background In domestic animals many biochemical and physiological processes exhibit daily rhythmicity. The aim of the present study was to investigate the rhythmic pattern of salivary and serum urea concentrations in sheep. Methods Six 3-year-old female sheep kept in the same environmental conditions were used. Sheep were sampled at 4 hour intervals for 48 consecutive hours starting at 08:00 of the first day and finishing at 04:00 of the second day. Blood samples were collected via intravenous cannulae inserted into the jugular vein; saliva samples were collected through a specific tube, the "Salivette". Salivary and serum urea concentrations were assayed by means of UV spectrophotometer. ANOVA was used to determine significant differences. The single Cosinor procedure was applied to the results showing significant differences over time. Results ANOVA showed a significant effect of time on salivary and serum urea concentrations. Serum and salivary urea peaked during the light phase. In the dark phase serum and salivary urea concentrations decreased, and the diurnal trough occurred at midnight. Cosinor analysis showed diurnal acrophases for salivary and serum urea concentrations. Daily mean levels were significantly higher in the serum than in the saliva. Conclusion In sheep both salivary and serum urea concentrations showed daily fluctuations. Urea is synthesized in the liver and its production is strongly influenced by food intake. Future investigation should clarify whether daily urea rhythms in sheep are endogenous or are simply the result of the temporal administration of food. PMID:17123442

Piccione, Giuseppe; Foà, Augusto; Bertolucci, Cristiano; Caola, Giovanni

2006-01-01

97

Urea Impedes the Hydrophobic Collapse of Partially Unfolded Proteins  

PubMed Central

Proteins are denatured in aqueous urea solution. The nature of the molecular driving forces has received substantial attention in the past, whereas the question how urea acts at different phases of unfolding is not yet well understood at the atomic level. In particular, it is unclear whether urea actively attacks folded proteins or instead stabilizes unfolded conformations. Here we investigated the effect of urea at different phases of unfolding by molecular dynamics simulations, and the behavior of partially unfolded states in both aqueous urea solution and in pure water was compared. Whereas the partially unfolded protein in water exhibited hydrophobic collapses as primary refolding events, it remained stable or even underwent further unfolding steps in aqueous urea solution. Further, initial unfolding steps of the folded protein were found not to be triggered by urea, but instead, stabilized. The underlying mechanism of this stabilization is a favorable interaction of urea with transiently exposed, less-polar residues and the protein backbone, thereby impeding back-reactions. Taken together, these results suggest that, quite generally, urea-induced protein unfolding proceeds primarily not by active attack. Rather, thermal fluctuations toward the unfolded state are stabilized and the hydrophobic collapse of partially unfolded proteins toward the native state is impeded. As a result, the equilibrium is shifted toward the unfolded state. PMID:19413980

Stumpe, Martin C.; Grubmüller, Helmut

2009-01-01

98

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

99

Urea formaldehyde foam: a dangerous insulation  

SciTech Connect

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

Keough, C.

1980-12-01

100

Effect of organic matter and urease inhibitors on urea hydrolysis and immobilization of urea nitrogen in an alkaline soil  

Microsoft Academic Search

Laboratory incubation experiments with 15N-labelled urea were conducted on a Aquic Udifluvent Belgian soil amended with barley straw, in, order to study the influence of three urease inhibitors, hydroquinone, phenyl phosphorodiamidate and N-(n-butyl) phosphorothioic triamide on urea hydrolysis and N transformations. The results demonstrated that the urea was hydrolyzed more rapidly when the soil was amended with ground barley straw.

Wang Zhengping; O. Van Cleemput; Li Liantie; L. Baert

1991-01-01

101

Combustion 2000  

SciTech Connect

This report is a presentation of work carried out on Phase II of the HIPPS program under DOE contract DE-AC22-95PC95144 from June 1995 to March 2001. The objective of this report is to emphasize the results and achievements of the program and not to archive every detail of the past six years of effort. These details are already available in the twenty-two quarterly reports previously submitted to DOE and in the final report from Phase I. The report is divided into three major foci, indicative of the three operational groupings of the program as it evolved, was restructured, or overtaken by events. In each of these areas, the results exceeded DOE goals and expectations. HIPPS Systems and Cycles (including thermodynamic cycles, power cycle alternatives, baseline plant costs and new opportunities) HITAF Components and Designs (including design of heat exchangers, materials, ash management and combustor design) Testing Program for Radiative and Convective Air Heaters (including the design and construction of the test furnace and the results of the tests) There are several topics that were part of the original program but whose importance was diminished when the contract was significantly modified. The elimination of the subsystem testing and the Phase III demonstration lessened the relevance of subtasks related to these efforts. For example, the cross flow mixing study, the CFD modeling of the convective air heater and the power island analysis are important to a commercial plant design but not to the R&D product contained in this report. These topics are of course, discussed in the quarterly reports under this contract. The DOE goal for the High Performance Power Plant System ( HIPPS ) is high thermodynamic efficiency and significantly reduced emissions. Specifically, the goal is a 300 MWe plant with > 47% (HHV) overall efficiency and {le} 0.1 NSPS emissions. This plant must fire at least 65% coal with the balance being made up by a premium fuel such as natural gas. To achieve these objectives requires a change from complete reliance of coal-fired systems on steam turbines (Rankine cycles) and moving forward to a combined cycle utilizing gas turbines (Brayton cycles) which offer the possibility of significantly greater efficiency. This is because gas turbine cycles operate at temperatures well beyond current steam cycles, allowing the working fluid (air) temperature to more closely approach that of the major energy source, the combustion of coal. In fact, a good figure of merit for a HIPPS design is just how much of the enthalpy from coal combustion is used by the gas turbine. The efficiency of a power cycle varies directly with the temperature of the working fluid and for contemporary gas turbines the optimal turbine inlet temperature is in the range of 2300-2500 F (1260-1371 C). These temperatures are beyond the working range of currently available alloys and are also in the range of the ash fusion temperature of most coals. These two sets of physical properties combine to produce the major engineering challenges for a HIPPS design. The UTRC team developed a design hierarchy to impose more rigor in our approach. Once the size of the plant had been determined by the choice of gas turbine and the matching steam turbine, the design process of the High Temperature Advanced Furnace (HITAF) moved ineluctably to a down-fired, slagging configuration. This design was based on two air heaters: one a high temperature slagging Radiative Air Heater (RAH) and a lower temperature, dry ash Convective Air Heater (CAH). The specific details of the air heaters are arrived at by an iterative sequence in the following order:-Starting from the overall Cycle requirements which set the limits for the combustion and heat transfer analysis-The available enthalpy determined the range of materials, ceramics or alloys, which could tolerate the temperatures-Structural Analysis of the designs proved to be the major limitation-Finally the commercialization issues of fabrication and reliability, availability and maintenance. The program that has s

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

2001-06-30

102

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

NASA Astrophysics Data System (ADS)

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

Banchorndhevakul, Siriwattana

2002-08-01

103

Combustion 2000  

SciTech Connect

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

None

1999-12-31

104

Fundamentals of Gas Turbine combustion  

NASA Technical Reports Server (NTRS)

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

Gerstein, M.

1979-01-01

105

Backpressure Routing Made Practical  

Microsoft Academic Search

Current data collection protocols for wireless sensor networks are mostly based on quasi-static minimum-cost routing trees. We consider an alternative, highly-agile approach called backpressure routing, in which routing and forwarding decisions are made on a per-packet basis. Although there is a considerable theoretical literature on backpressure routing, it has not been implemented on practical systems to date due to concerns

Scott Moeller; Avinash Sridharan; Bhaskar Krishnamachari; Omprakash Gnawali

2010-01-01

106

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

107

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

Code of Federal Regulations, 2011 CFR

...2011-07-01 2011-07-01 false Urea, (hexahydro-6-methyl-2-oxopyrimidinyl...Specific Chemical Substances § 721.9920 Urea, (hexahydro-6-methyl-2-oxopyrimidinyl...reporting. (1) The chemical substance urea,...

2011-07-01

108

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

Code of Federal Regulations, 2011 CFR

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

2011-07-01

109

Ocean urea fertilization for carbon credits poses high ecological risks  

Microsoft Academic Search

The proposed plan for enrichment of the Sulu Sea, Philippines, a region of rich marine biodiversity, with thousands of tonnes of urea in order to stimulate algal blooms and sequester carbon is flawed for multiple reasons. Urea is preferentially used as a nitrogen source by some cyanobacteria and dinoflagellates, many of which are neutrally or positively buoyant. Biological pumps to

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

2008-01-01

110

Measuring urea persistence, distribution and transport on coastal plain soils  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

111

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

112

Branchial and renal urea transport mechanisms in three teleost fish  

Microsoft Academic Search

Physiological and pharmacological approaches were used to characterize the pulsatile, facilitated diffusion urea transport mechanism (tUT) known from molecular evidence to be present in the gills of the facultatively ureotelic gulf toadfish (Opsanus beta). Using those findings, potential urea transport mechanisms in the kidney of the toadfish and in both excretory organs of the ammoniotelic plainfin midshipman (Porichthys notatus), closely

M. Danielle McDonald

2002-01-01

113

Molecular Basis of the Apparent Near Ideality of Urea Solutions.  

SciTech Connect

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

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

2007-11-01

114

Managing Urea-Containing Fertilizers1 Larry G. Bundy2  

E-print Network

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

Balser, Teri C.

115

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

116

Rapid method for detection of urea hydrolysis by yeasts.  

PubMed Central

A method is described for the rapid detection of urea hydrolysis by yeasts, using the Berthelot color reaction. The results could be determined within 30 to 50 min with this method, compared with 8 to 72 h usually required with Christensen urea agar. PMID:322609

Paliwal, D K; Randhawa, H S

1977-01-01

117

Combustion Modeling in Internal Combustion Engines  

Microsoft Academic Search

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

FRANK J. ZELEZNIK

1976-01-01

118

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

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

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

121

Adiabatic internal combustion engine  

Microsoft Academic Search

An adiabatic internal combustion engine is described comprising a cylinder having a piston movably disposed therein, means for admitting air and fuel to the cylinder to be combusted therein and means for discharging the combustion gases therefrom, the cylinder including a piston guide and seal structure having stationary seal rings associated therewith and, the cylinder having an inner wall structure

C. E. Kraus; C. B. Lohr

1989-01-01

122

Internal combustion engine  

Microsoft Academic Search

An internal combustion engine is described which utilizes a combustion cylinder formed in part of material which can withstand high temperatures in conjunction with a displacement or power piston having a ringless section capable of withstanding high temperatures and being backed up by a relatively low temperature lubricated ringed piston section. Means to inject fuel and water into the combustion

Thomas

1976-01-01

123

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

124

Functionalized multilayered graphene platform for urea sensor.  

PubMed

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

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

2012-01-24

125

State alternative route designations  

SciTech Connect

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

Not Available

1989-07-01

126

State alternative route designations  

SciTech Connect

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

Not Available

1989-07-01

127

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

Microsoft Academic Search

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

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

1983-01-01

128

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

129

Opportunities in pulse combustion  

SciTech Connect

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

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

1985-10-01

130

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

131

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

132

Structural Characterization of Apomyoglobin Self-Associated Species in Aqueous Buffer and Urea Solution  

PubMed Central

The biophysical characterization of nonfunctional protein aggregates at physiologically relevant temperatures is much needed to gain deeper insights into the kinetic and thermodynamic relationships between protein folding and misfolding. Dynamic and static laser light scattering have been employed for the detection and detailed characterization of apomyoglobin (apoMb) soluble aggregates populated at room temperature upon dissolving the purified protein in buffer at pH 6.0, both in the presence and absence of high concentrations of urea. Unlike the ?-sheet self-associated aggregates previously reported for this protein at high temperatures, the soluble aggregates detected here have either ?-helical or random coil secondary structure, depending on solvent and solution conditions. Hydrodynamic diameters range from 80 to 130 nm, with semiflexible chain-like morphology. The combined use of low pH and high urea concentration leads to structural unfolding and complete elimination of the large aggregates. Even upon starting from this virtually monomeric unfolded state, however, protein refolding leads to the formation of severely self-associated species with native-like secondary structure. Under these conditions, kinetic apoMb refolding proceeds via two parallel routes: one leading to native monomer, and the other leading to a misfolded and heavily self-associated state bearing native-like secondary structure. PMID:16214860

Chow, Charles; Kurt, Ne?e; Murphy, Regina M.; Cavagnero, Silvia

2006-01-01

133

Structural characterization of apomyoglobin self-associated species in aqueous buffer and urea solution.  

PubMed

The biophysical characterization of nonfunctional protein aggregates at physiologically relevant temperatures is much needed to gain deeper insights into the kinetic and thermodynamic relationships between protein folding and misfolding. Dynamic and static laser light scattering have been employed for the detection and detailed characterization of apomyoglobin (apoMb) soluble aggregates populated at room temperature upon dissolving the purified protein in buffer at pH 6.0, both in the presence and absence of high concentrations of urea. Unlike the beta-sheet self-associated aggregates previously reported for this protein at high temperatures, the soluble aggregates detected here have either alpha-helical or random coil secondary structure, depending on solvent and solution conditions. Hydrodynamic diameters range from 80 to 130 nm, with semiflexible chain-like morphology. The combined use of low pH and high urea concentration leads to structural unfolding and complete elimination of the large aggregates. Even upon starting from this virtually monomeric unfolded state, however, protein refolding leads to the formation of severely self-associated species with native-like secondary structure. Under these conditions, kinetic apoMb refolding proceeds via two parallel routes: one leading to native monomer, and the other leading to a misfolded and heavily self-associated state bearing native-like secondary structure. PMID:16214860

Chow, Charles; Kurt, Nese; Murphy, Regina M; Cavagnero, Silvia

2006-01-01

134

Combustion modeling in internal combustion engines  

NASA Technical Reports Server (NTRS)

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

Zeleznik, F. J.

1976-01-01

135

Routing Without Routes: The Backpressure Collection Scott Moeller  

E-print Network

Routing Without Routes: The Backpressure Collection Protocol Scott Moeller , Avinash Sridharan trees. We consider an alternative, highly-agile approach called backpressure routing, in which routing on backpressure routing, it has not been implemented on practical systems to date due to concerns about packet

Krishnamachari, Bhaskar

136

Online measurement of urea concentration in spent dialysate during hemodialysis  

NASA Astrophysics Data System (ADS)

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

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

2002-05-01

137

CONTROL OF DIESEL ENGINE UREA SELECTIVE CATALYTIC REDUCTION SYSTEMS.  

E-print Network

??A systematic nonlinear control methodology for urea-SCR systems applicable for light-to-heavy-duty Diesel engine platforms in a variety of on-road, off-road, and marine applications is developed… (more)

Hsieh, Ming-Feng

2010-01-01

138

21 CFR 862.1770 - Urea nitrogen test system.  

Code of Federal Regulations, 2012 CFR

...DRUG 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) Identification....

2012-04-01

139

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. ...

140

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

141

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...

142

Hydrogen production via urea electrolysis using a gel electrolyte  

NASA Astrophysics Data System (ADS)

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

King, Rebecca L.; Botte, Gerardine G.

2011-03-01

143

Reinvestigation of growth of thiourea urea zinc sulfate crystal  

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

144

Correcting Nitrogen Deficiencies in Cotton with Urea-Based Products  

E-print Network

Correcting nitrogen deficiency is important for cotton plant growth. This publication explains nitrogen requirements, the problems associated with nitrogen deficiency, and ways to correct deficiencies using urea as a source of nitrogen....

Livingston, Stephen; Stichler, Charles

1995-11-22

145

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

PubMed

Heterostructured BiOBr/Bi24O31Br10 nanocomposites with surface oxygen vacancies are constructed by a facile in situ route of one-step self-combustion of ionic liquids. The compositions can be easily controlled by simply adjusting the fuel ratio of urea and 2-bromoethylamine hydrobromide (BTH). BTH serves not only as a fuel, but also as a complexing agent for ionic liquids and a reactant to supply the Br element. The heterojunctions show remarkable adsorptive ability for both the cationic dye of rhodamine B (RhB) and the anionic dye of methylene orange (MO) at high concentrations, which is attributed to the abundant surface oxygen vacancies. The sample containing 75.2% BiOBr and 24.8% Bi24O31Br10 exhibits the highest photocatalytic activity. Its reaction rate constant is 4.0 and 9.0 times that of pure BiOBr in degrading 50 mg L(-1) of RhB and 30 mg L(-1) of MO under visible-light (? > 400 nm) irradiation, respectively, which is attributed to the narrow band gap and highly efficient transfer efficiency of charge carriers. Different photocatalytic reaction processes and mechanisms over pure BiOBr and heterojunctions are proposed. PMID:25482071

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

2014-12-18

146

Coal combustion products  

USGS Publications Warehouse

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

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

2001-01-01

147

Solid-state urea biosensor based on the differential method  

Microsoft Academic Search

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

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

2006-01-01

148

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

149

Combustion under microgravity conditions  

SciTech Connect

Reduced gravity combustion experiments are frequently required to provide the information necessary for comprehensive understanding of combustion phenomena at normal gravitational conditions. Previous papers have dealt in detail with a broad range of combustion science experiments which require reduced gravity experimentation. This paper enlarges on these previous studies. Reduced gravity experiments are shown to be needed for comprehensive understanding of kinetic and thermokinetic oscillatory flame processes, the radiative ignition of solids, high pressure flame propagation and extinction phenomena, as well as a number of other combustion science areas of vital interest.

Berlad, A.L.

1982-01-01

150

Analysis of the Sub-Millimeter Rotational Spectrum of Urea  

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

151

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

152

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

153

Onion routing access configurations  

Microsoft Academic Search

Onion Routing is an infrastructure for private communication over a public network. It provides anonymous connections that are strongly resistant to both eavesdropping and traffic analysis. Thus it hides not only the data being sent, but who is talking to whom. Onion Routing's anonymous connections are bidirectional and near real-time, and can be used anywhere a socket connection can be

Paul Syverson; Michael Reed; David Goldschlag

2000-01-01

154

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

Microsoft Academic Search

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

D. L. Palmquist

1993-01-01

155

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

SciTech Connect

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

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

2009-01-15

156

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.

2014-09-14

157

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

158

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

159

Application of selective non-catalytic reduction of NO x in small-scale combustion systems  

Microsoft Academic Search

The selective non-catalytic reduction of NOx has been studied experimentally employing commercial grade urea in a pilot-scale diesel-fired tunnel furnace at 3–4% excess oxygen level and with low ppm of baseline NOx ranging from 65 to 75ppm within the investigated temperature range. The furnace simulated the thermal behavior of small-scale combustion systems such as small capacity boilers, water heaters, oil

Khandoker Abul Hossain; Mohammad Nazri Mohd Jaafar; Azeman Mustafa; Kiran Babu Appalanidu; Farid Nasir Ani

2004-01-01

160

Application of selective non-catalytic reduction of NOx in small-scale combustion systems  

Microsoft Academic Search

The selective non-catalytic reduction of NOx has been studied experimentally employing commercial grade urea in a pilot-scale diesel-fired tunnel furnace at 3-4% excess oxygen level and with low ppm of baseline NOx ranging from 65 to 75 ppm within the investigated temperature range. The furnace simulated the thermal behavior of small-scale combustion systems such as small capacity boilers, water heaters,

Khandoker Abul Hossain; Mohammad Nazri Mohd Jaafar; Azeman Mustafa; Kiran Babu Appalanidu; Farid Nasir Ani

2004-01-01

161

Effect of propellant on the combustion synthesized Sr-doped LaMnO 3 powders  

Microsoft Academic Search

Lanthanum strontium manganite (LSM) powders of composition La0.7Sr0.3MnO3 are good candidates for cathode application in solid oxide fuel cells. This paper reports the synthesis of LSM powders from nitrate precursors by the combustion method, using two different propellants (urea and glycine) and varying the propellant\\/nitrate ratio. Thermogravimetric analysis (TGA) revealed two or three decomposition stages of the as-synthesized samples, with

Leandro da Conceição; Nielson F. P. Ribeiro; José Geraldo M. Furtado; Mariana M. V. M. Souza

2009-01-01

162

Combustion synthesis and photoluminescence of Nd 3+-doped YPO 4 nanocrystals  

Microsoft Academic Search

Nd3+-doped YPO4 nanocrystals were synthesized by combustion method with urea as a fuel calcined at 600°C. The diffraction profile of the obtained sample was indexed as a tetragonal xenotime structure by X-ray diffraction (XRD) data. The obtained nanocrystals appeared to be spherical with some agglomeration and their sizes ranged from 30 to 50nm. The luminescence intensities of Nd3+-doped YPO4 nanocrystals

Suwen Liu; Zhiliang Xiu; Fengxiu Xu; Weina Yu; Jiaoxian Yu; Guangjian Feng

2008-01-01

163

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

164

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

165

External combustion rotary engine  

Microsoft Academic Search

A rotary piston external combustion engine is described comprising: means for compressing air and expanding combusted gas; a shaft connected to the compressing and expanding means for delivering power by means of an external drive shaft; an air inlet port opening for admitting ambient air in the air compressing means; an outlet valve for venting the compressed air out when

1988-01-01

166

Internal combustion engine  

Microsoft Academic Search

This patent describes an internal combustion engine of the two-cycle type. It comprises a cylinder, a piston slidable within the cylinder, a cylinder head to seal the cylinder at the top, thereby defining a combustion chamber, a crankshaft means to provide reciprocating motion to the piston, a lubricating means to lubricate the crankshaft, a sealing means around the bottom of

Van Blaricom

1992-01-01

167

Coal Combustion Science  

SciTech Connect

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

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

1991-08-01

168

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

169

Internal combustion engine with rotary combustion chamber  

Microsoft Academic Search

This patent describes an internal combustion engine comprising: a block having at least one cylindrical wall surrounding a piston chamber, piston means located in the piston chamber means operable to reciprocate the piston means in the chamber, head means mounted on the block covering the chamber. The head means has an air and fuel intake passage, and exhaust gas passage,

C. N. Hansen; P. C. Cross

1986-01-01

170

Internal combustion engine with rotary combustion chamber  

Microsoft Academic Search

This patent describes an internal combustion engine comprising: a block having at least one cylindrical wall surrounding a piston chamber, piston means located in the piston chamber, means operable to reciprocate the piston means in the chamber, head means mounted on the block covering the chamber. The head means having an air and fuel intake passage, an exhaust gas passage,

C. N. Hansen; P. C. Cross

1988-01-01

171

Combustion control system for internal combustion engines  

Microsoft Academic Search

This patent describes a modified spark plug for internal combustion engines comprising: a base made of an electrically conductive material and adapted to be installed in the engine; an insulator disposed within the base and having a precombustion chamber formed therein; a central electrode passing through the insulator, extending into the precombustion chamber and defining a passageway in communication with

1988-01-01

172

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

PubMed

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, however, no GS activity was detected, and GOGAT activity was only present in S. ureae. GDH enzymes were present in these two organisms, but showed only low affinity for ammonium, with apparent Km-values of 55.2 mM in B. pasteurii and 36.7 mM in S. ureae, respectively. These observations explain why P. vulgaris is able to grow at neutral pH and low ammonium concentration (2 mM), while B. pasteurii and S. ureae require high ammonium concentration (40 mM) and alkaline pH for growth. PMID:2570557

Mörsdorf, G; Kaltwasser, H

1989-01-01

173

Structure of divided combustion chamber for internal combustion engine  

Microsoft Academic Search

This patent describes a structure defining a divided combustion chamber of an internal combustion engine, comprising an upper ceramic member, and a lower ceramic member having a transfer passage which communicates with a main combustion chamber of the engine. The upper and lower ceramic members meet with each other at an interface to form divided combustion chamber such that it

Y. Ogawa; T. Ogasawara; S. Hanzawa

1987-01-01

174

WhatRoute  

NSDL National Science Digital Library

How does your data travel? It's a great question, and one that can be answered via the use of WhatRoute. This application is a network diagnostic utility that allows users to see the geographical route of the paths that packets from your computer take as they traverse the Internet. The results can also be viewed via Google Earth, which is quite a dramatic experience. This version is compatible with computers running Mac OS X and newer.

Christianson, Bryan

2012-07-28

175

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

176

Winged reentrant electromagnetic combustion chamber  

Microsoft Academic Search

An internal combustion engine combustion chamber suitable for electromagnetic stimulation of combustion which has been improved by the addition of combustion chamber periphery extensions (wings) filled with dielectric material. The wing dimensions and filler dielectric material are chosen to allow for specification of the chamber EM resonant frequency, preferably at a frequency in the UHF range (where low cost DC

M. A. V

1985-01-01

177

Wire routing by Lagrangian method  

Microsoft Academic Search

Routing problems have been formulated as discrete optimization problems. The maze router has been widely used because of its ability to find a shortest path. The weakness of the maze router is that the routing quality is dependent on the ordering of the nets to be routed. We propose a new algorithm which solves the routing problem as a continuous

M. Nagamatu; S. Ismail; R. Shinji; T. Yanaru

1995-01-01

178

Bees_ Ants Based Routing Algorithm  

Microsoft Academic Search

In this paper we propose a novel routing algorithm called Bees_Ants algorithm. This algorithm is a combination of ant colony based routing algorithm (ARA) and BeeHive based routing algorithm. The proposed routing algorithm depends on splitting the network into two parts; one is a fixed network and the other is a mobile ad hoc network (MANET), then applying the ant

Eslam Al Maghayreh; Salam Abu Al-Haija; Faisal Alkhateeb; Shadi Aljawarneh

2010-01-01

179

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

180

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

181

Monitoring of Urea and Potassium by Reverse Iontophoresis In Vitro  

Microsoft Academic Search

Purpose  Reverse iontophoresis is an alternative to blood sampling for the monitoring of endogenous molecules. Here, the potential\\u000a of the technique to measure urea and potassium levels non-invasively, and to track their concentrations during hemodialysis,\\u000a has been examined.\\u000a \\u000a \\u000a \\u000a Materials and Methods  \\u000a In vitro experiments were performed to test (a) a series of subdermal urea and potassium concentrations typical of the pathophysiologic

Valentine Wascotte; M. Begoña Delgado-Charro; Eric Rozet; Pierre Wallemacq; Philippe Hubert; Richard H. Guy; Véronique Préat

2007-01-01

182

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

PubMed

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

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

2013-06-01

183

Effects of high ambient temperature on urea-nitrogen recycling in lactating dairy cows.  

PubMed

Effects of exposure to hot environment on urea metabolism were studied in lactating Holstein cows. Four cows were fed ad libitum a total mixed ration and housed in a temperature-controlled chamber at constant moderate (18°C) or high (28°C) ambient temperatures in a cross-over design. Urea nitrogen (N) kinetics was measured by determining urea isotopomer in urine after single injection of [(15) N(2) ]urea into the jugular vein. Both dry matter intake and milk yield were decreased under high ambient temperature. Intakes of total N and digestible N were decreased under high ambient temperature but urinary urea-N excretion was increased. The ratio of urea-N production to digestible N was increased, whereas the proportion of gut urea-N entry to urea-N production tended to be decreased under high ambient temperature. Neither return to the ornithine cycle, anabolic use nor fecal excretion of urea-N recycled to the gut was affected by ambient temperature. Under high ambient temperature, renal clearance of plasma urea was not affected but the gut clearance was decreased. Increase of urea-N production and reduction of gut urea-N entry, in relative terms, were associated with increased urinary urea-N excretion of lactating dairy cows in higher thermal environments. PMID:21794010

Obitsu, Taketo; Kamiya, Mitsuru; Kamiya, Yuko; Tanaka, Masahito; Sugino, Toshihisa; Taniguchi, Kohzo

2011-08-01

184

Studies in premixed combustion  

SciTech Connect

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

Sivashinsky, G.I.

1992-01-01

185

Combustion in fluidized beds  

Microsoft Academic Search

Circulating fluidized-bed (CFB) combustion systems have become popular since the late 1970s, and, given the current level of activity in the area,it is clear that this technology has a stable future in the boiler market. For standard coal combustion applications, competition is fierce with mature pulverized-fuel-based (PF) technology set to maintain a strong profile. CFB systems, however, can be more

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

1990-01-01

186

pH-Dependent urea-induced unfolding of stem bromelain: unusual stability against urea at neutral pH.  

PubMed

Equilibrium unfolding of stem bromelain (SB) with urea as a denaturant has been monitored as a function of pH using circular dichroism and fluorescence emission spectroscopy. Urea-induced denaturation studies at pH 4.5 showed that SB unfolds through a two-state mechanism and yields DeltaG (free energy difference between the fully folded and unfolded forms) of approximately 5.0 kcal/mol and C(m) (midpoint of the unfolding transition) of approximately 6.5 M at 25 degrees C. Very high concentration of urea (9.5 M) provides unusual stability to the protein with no more structural loss and transition to a completely unfolded state. PMID:19961414

Ahmad, B; Rathar, G M; Varshney, A; Khan, R H

2009-12-01

187

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

188

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

Code of Federal Regulations, 2011 CFR

...2011-07-01 2011-07-01 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...

2011-07-01

189

Imposed Route Reuse in Ad Hoc Network Routing Protocols Using Structured Peer-to-Peer Overlay Routing  

Microsoft Academic Search

One of the most effective approaches to reducing the routing overhead in mobile ad hoc network routing protocols is to reuse routes discovered for one packet to deliver as many other packets as possible. Numerous techniques have been developed to facilitate route reuse, including caching, overhearing, using partial routes, and replying to route discovery with cached routes. We term such

Himabindu Pucha; Saumitra M. Das; Y. Charlie Hu

2006-01-01

190

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

PubMed Central

Urea transporters facilitate urea permeation across cell membranes in prokaryotes and eukaryotes. Bacteria use urea either as a means to survive in acidic environments and/or as a nitrogen source. The urea transporter ApUT from Actinobacillus pleuropneumoniae, the pathogen that causes porcine pleurisy and pneumonia, was expressed in E. coli and purified. Analysis of the recombinant protein using cross-linking and blue-native gel electrophoresis established that ApUT is a dimer in detergent solution. To determine the urea transport kinetics of ApUT, purified protein was reconstituted into proteoliposomes, and urea efflux was measured by stopped-flow fluorometry. The measured urea flux was saturable, could be inhibited by phloretin, and was not affected by pH. Two-dimensional crystals of the biologically active ApUT show that it is also dimeric in a lipid membrane and provide the first structural information on a member of the urea transporter family. PMID:19361419

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

2009-01-01

191

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

192

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

E-print Network

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

Priyakumar, U Deva; Thirumalai, D; MacKerell, Alexander D

2009-01-01

193

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

E-print Network

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

U. Deva Priyakumar; Changbong Hyeon; D. Thirumalai; Alexander D. MacKerell Jr

2009-12-07

194

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

Code of Federal Regulations, 2011 CFR

...Environment 31 2011-07-01 2011-07-01 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)....

2011-07-01

195

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

196

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

Code of Federal Regulations, 2010 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...

2010-07-01

197

Combustion synthesis of YAG:Ce and related phosphors  

NASA Astrophysics Data System (ADS)

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

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

2011-11-01

198

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

199

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

Microsoft Academic Search

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

Zhengpeng Yang; Shihui Si; Hongjuan Dai; Chunjing Zhang

2007-01-01

200

Reduction in slow intercompartmental clearance of urea during dialysis  

SciTech Connect

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

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

1985-04-01

201

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

202

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...

203

Some studies on starch–urea–acid reaction mechanism  

Microsoft Academic Search

Starch reacted with urea in the absence or presence of mineral acids or mineral acid salts at 150°C for various reaction durations. The acids used were phosphoric, nitric, and sulphuric and the salts used were ammonium sulphate, ammonium nitrate, ammonium chloride and magnesium sulphate. The reaction extent was followed by monitoring nitrogen content. Carrying out the reaction of starch and

M. I Khalil; S Farag; A. A Aly; A Hebeish

2002-01-01

204

Pt nanoflower/polyaniline composite nanofibers based urea biosensor.  

PubMed

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

Jia, Wenzhao; Su, Liang; Lei, Yu

2011-12-15

205

Using urea to decompose polylactic acid in bark compost  

Microsoft Academic Search

Polylactic acid (PLA) is a plastic of plant origin. Because it is biodegradable, it is used for various environmentally friendly materials, such as sand bags and mulching sheets for agriculture and construction. However, PLA biodegrades very slowly and only a few microorganisms can biodegrade it. We tested a biodegrading method that uses urea to accelerate the decomposition of PLA cloth

Kenji Nakamura

206

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

207

Collective network routing  

DOEpatents

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

Hoenicke, Dirk

2014-12-02

208

On Compact Routing for the Internet  

Microsoft Academic Search

The Internet's routing system is facing stresses due to its poor fundamental scaling properties. Compact routing is a research field that studies fundamental limits of routing scalability and designs algorithms that try to meet these limits. In particular, compact routing research shows that shortest-path routing, forming a core of traditional routing algorithms, cannot guarantee routing table (RT) sizes that on

Dmitri V. Krioukov; Kimberly C. Claffy; Kevin R. Fall; Arthur Brady

2007-01-01

209

The Combustive Sound Source  

NASA Astrophysics Data System (ADS)

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

Wilson, Preston S.

1994-04-01

210

Crystal growth and nonlinear optical studies of m-dinitrobenzene doped urea  

Microsoft Academic Search

Urea is an attractive material for frequency conversion of high power lasers to UV but the frequent use of urea (U) crystal at normal atmosphere is troublesome due to its hygroscopic nature. The hygroscopic character of urea has been modified by making the solid solution with m-dinitrobenzene (DNB). The phase diagram of DNB and U shows the formation of a

R. N. Rai; S. R. Mudunuri; R. S. B. Reddi; V. S. A. Kumar Satuluri; S. Ganeshmoorthy; P. K. Gupta

2011-01-01

211

Urea-Induced Denaturation of PreQ1Riboswitch Jeseong Yoon,  

E-print Network

components of nucleotides makes urea a powerful chemical denaturant for nucleic acids. INTRODUCTION Neutral with the bases. Through detailed studies of the simulation trajectories, we found that geminate pairs between urea and bases due to hydrogen bonds and stacks persist only 0.1-1 ns, which suggests that the urea-base

Thirumalai, Devarajan

212

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

E-print Network

1 Judith Beekman and Ronald L. Thune Evaluation of the Role of Ammonia and Urea Transporters and ammonia transporters in a urease gene cluster · Hypothesis: The E. ictaluri urea and ammonia transporters are actively expressed ­Aim 1. Demonstrate transcription of the E. ictaluri urea and ammonia transporters ­Aim

Kane, Andrew S.

213

Urea cycling and ammonia absorption in vivo in the digestive tract of the rat  

E-print Network

Urea cycling and ammonia absorption in vivo in the digestive tract of the rat C. DEMIGNÃ? C. RÃ?MÃ?SY. The transfer of blood urea into the digestive tract and ammonia absorption at that site have been studied in vivo in anesthetized rats. The vein-artery differences in urea and ammonia absorption were greater

Paris-Sud XI, Université de

214

ORIGINAL PAPER Urea-induced hypometabolism in the hibernating wood frog  

E-print Network

ORIGINAL PAPER Urea-induced hypometabolism in the hibernating wood frog (Rana sylvatica-induced hypometabolism observed in hibernating R. sylvatica results from inhibition of energy-utilizing processes urea depresses metabolic rate. Keywords Mitochondria Á Metabolism Á Urea Á Hibernation Á Rana sylvatica

Lee Jr., Richard E.

215

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

Microsoft Academic Search

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

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

1996-01-01

216

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

Federal Register 2010, 2011, 2012, 2013, 2014

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

2010-12-15

217

Effect of the Protein Denaturants Urea and Guanidinium on Water Structure: A Structural and Thermodynamic Study  

E-print Network

Effect of the Protein Denaturants Urea and Guanidinium on Water Structure: A StructuralVania 19104-6059 ReceiVed May 4, 1998 Abstract: The mechanism of the denaturing effects of urea of denaturation is discussed. Introduction The mechanism by which urea and the guanidinium ion denature proteins

Sharp, Kim

218

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

E-print Network

Urea denaturation by stronger dispersion interactions with proteins than water implies a 2-stage of denaturation of proteins by urea is explored by using all-atom microseconds molecular dynamics simulations mechanism'' whereby urea has a stronger dispersion interaction with protein than water. denaturing mechanism

Thirumalai, Devarajan

219

Detailed modeling of the evaporation and thermal decomposition of urea-water-solution in SCR systems  

E-print Network

Detailed modeling of the evaporation and thermal decomposition of urea-water-solution in SCRE Journal. Keywords: Multi-component, , evaporation, UWS, Adbue, urea decomposition, thermolysis SCR, kinetics Abstract This work aims to develop a multi-component evaporation model for droplets of urea

Boyer, Edmond

220

PHYSIOLOGY AND YIELD RESPONSES OF COTTON TO FOLIAR UREA WITH NBPT  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

221

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

222

Combustion synthesis process for the rapid preparation of high-purity SrO powders  

NASA Astrophysics Data System (ADS)

A rapid, safe and simple technique for the production of high purity strontium oxide powders via a chemical combustion process is reported. The combustion reactions were performed to optimize the fuel to oxidizer ratios in the reaction mixtures required to obtain pure SrO powders by varying the molar ratio of chemical precursors and the temperature. The synthesized powders were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectrometry, infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis, and N2-physisorption measurements. The results indicate that crystalline SrO was obtained using a 1:1 strontium nitrate: urea molar ratio at 1000 °C after 5 minutes. In addition, high-purity, homogeneous and crystalline SrO powders were easily produced in a short time via a chemical combustion process.

Granados-Correa, Francisco; Bonifacio-Martínez, Juan

2014-12-01

223

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

224

Combustion in fluidized beds  

SciTech Connect

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

Dry, F.J.; La Nauze, R.D. (CSIRO, Div. of Mineral and Process Engineering, Clayton, Victoria 3168 (AU))

1990-07-01

225

Microgravity Combustion Diagnostics Workshop  

NASA Technical Reports Server (NTRS)

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

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

1988-01-01

226

High efficiency RCCI combustion  

NASA Astrophysics Data System (ADS)

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

Splitter, Derek A.

227

Pictorial Representations of Routes: Chunking Route Segments during Comprehension  

Microsoft Academic Search

Route directions are usually conveyed either by graphical means, i.e. by illustrating the route in a map or drawing a sketch-maps or, linguistically by giving spoken or written route instructions, or by combining both kinds of external representations. In most cases route directions are given in advance, i.e. prior to the actual traveling. But they may also be communicated quasi-

Alexander Klippel; Heike Tappe; Christopher Habel

2003-01-01

228

Submarine cable route survey  

SciTech Connect

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

Herrouin, G.; Scuiller, T.

1995-12-31

229

Hydrologic Flood Routing.  

ERIC Educational Resources Information Center

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

Heggen, Richard J.

1982-01-01

230

Droplet Combustion Experiment movie  

NASA Technical Reports Server (NTRS)

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

2003-01-01

231

Fluidized-bed combustion  

SciTech Connect

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

Botros, P E

1990-04-01

232

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

233

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

234

Internal combustion engine  

DOEpatents

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

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

1991-01-01

235

Combustion wave instability in the filtration combustion of gases  

Microsoft Academic Search

Theoretical and experimental approaches to the problem of combustion wave stability in gas filtration combustion are described. An approximate criterion of instability for an initially plane combustion wave front is suggested within the framework of a hydrodynamic model. It is shown that the wave instabiliry cannot be observed if the reactor diameter is under a critical value. The critical value

S. S. Minaev; S. I. Potytnyakov; V. S. Babkin

1994-01-01

236

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

237

Routes to Novel Azo compounds   

E-print Network

Routes to novel heterocyclic azo compounds and components of use as potential inkjet dyes were investigated. A new route to fluorenones from biphenyl acid chlorides using FVP (Flash Vacuum Pyrolysis) has been discovered. ...

Iannarelli, Paul M.

238

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

239

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

240

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

241

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. ...

242

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

PubMed Central

To explain the large, opposite effects of urea and glycine betaine (GB) on stability of folded proteins and protein complexes, we quantify and interpret preferential interactions of urea with 45 model compounds displaying protein functional groups and compare with a previous analysis of GB. This information is needed to use urea as a probe of coupled folding in protein processes and to tune molecular dynamics force fields. Preferential interactions between urea and model compounds relative to their interactions with water are determined by osmometry or solubility and dissected using a unique coarse-grained analysis to obtain interaction potentials quantifying the interaction of urea with each significant type of protein surface (aliphatic, aromatic hydrocarbon (C); polar and charged N and O). Microscopic local-bulk partition coefficients Kp for the accumulation or exclusion of urea in the water of hydration of these surfaces relative to bulk water are obtained. Kp values reveal that urea accumulates moderately at amide O and weakly at aliphatic C, whereas GB is excluded from both. These results provide both thermodynamic and molecular explanations for the opposite effects of urea and glycine betaine on protein stability, as well as deductions about strengths of amide NH—amide O and amide NH—amide N hydrogen bonds relative to hydrogen bonds to water. Interestingly, urea, like GB, is moderately accumulated at aromatic C surface. Urea m-values for protein folding and other protein processes are quantitatively interpreted and predicted using these urea interaction potentials or Kp values. PMID:21930943

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

2011-01-01

243

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

244

Group combustion of coal particles  

Microsoft Academic Search

Group Combustion studies predict the effect of interactions on ignition and\\/or combustion of droplet\\/particle sprays\\/suspensions. The model presented in the current work deals with the iteractive combustion of a spherical cloud of uniformly spaced monosized coal particles. A method of correcting gas phase and particle kinetics when combustion becomes locally diffusion controlled allows for the use of rather large time

Ryan

1992-01-01

245

Cognitively Ergonomic Route Alexander Klippel  

E-print Network

Cognitively Ergonomic Route Directions Alexander Klippel C R C - S p a t i a l I n f o r m a t i o principles that allow us to define what makes route directions cognitively ergonomic, technical aspects for cognitively ergonomic route directions (Denis, 1997; Lovelace, Hegarty, & Montello, 1999; Tversky & Lee, 1999

Klippel, Alexander

246

Fast printed circuit board routing  

Microsoft Academic Search

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

Jeremy Dion

1987-01-01

247

Geographic routing without location information  

Microsoft Academic Search

For many years, scalable routing for wireless communication systems was a compelling but elusive goal. Recently, several routing algorithms that exploit geographic information (e.g. GPSR) have been proposed to achieve this goal. These algorithms refer to nodes by their location, not address, and use those coordinates to route greedily, when possible, towards the destination. However, there are many situations where

Ananth Rao; Sylvia Ratnasamy; Christos Papadimitriou; Scott Shenker; Ion Stoica

2003-01-01

248

Certificateless Onion Routing Dario Catalano  

E-print Network

Certificateless Onion Routing Dario Catalano Dipartimento di Matematica e Informatica Università di 10532 rosario@us.ibm.com ABSTRACT Onion routing protocols allow users to establish anonymous channels- posed in recent years, and TOR, a real-life implementation, provides an onion routing service

Catalano, Dario

249

Using directionality in mobile routing  

Microsoft Academic Search

The increased usage of directional methods of commu- nications has prompted research into leveraging direction- ality in every layer of the network stack. In this paper, we explore the use of directionality in layer 3 to facilitate routing in highly mobile environments. We introduce Mo- bile Orthogonal Rendezvous Routing Protocol (MORRP), a lightweight, but scalable routing protocol utilizing di- rectional

Bow-Nan Cheng; Murat Yuksel; Shivkumar Kalyanaraman

2010-01-01

250

Using directionality in mobile routing  

Microsoft Academic Search

The increased usage of directional methods of communications has prompted research into leveraging directionality in every layer of the network stack. In this paper, we explore the use of directionality in layer 3 to facilitate routing in highly mobile environments. We introduce mobile orthogonal rendezvous routing protocol (MORRP), a lightweight, but scalable routing protocol utilizing directional communications (such as directional

Bow-Nan Cheng; Murat Yuksel; Shivkumar Kalyanaraman

2008-01-01

251

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

PubMed

Recently, choline chloride/urea (ChCl/urea), a typical deep eutectic solvent (DES), has been found to possess various applications in organic synthesis, electrochemistry, and nanomaterial preparation. Herein we reported the first attempt to plasticize regenerated cellulose film (RCF) using ChCl/urea as an effective plasticizer. Meanwhile, RCFs plasticized with glycerol and sorbitol were also prepared for comparison. The plasticized RCFs were investigated by Fourier transform infrared (FT-IR) spectroscopy, wide-angle X-ray diffraction (XRD), atomic force microscopy (AFM), and mechanical testing. Transparent and soft RCFs could be successfully prepared in the presence of ChCl/urea, and high elongation at break (34.88%) suggested a significant plasticizing efficiency. No new crystal and phase separation occurred to ChCl/urea plasticized RCFs. The thermal stability of ChCl/urea plasticized RCF was lowered. These results indicated that ChCl/urea was an effective plasticizer for producing cellulose films. PMID:25498618

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

2015-03-01

252

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

253

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

254

Biomass combustion for power generation  

Microsoft Academic Search

An overview is given of the state of the art of biomass combustion power generation technologies with a capacity of more than 10 MWe. Biomass combustion technologies have been compared on a qualitative basis and a selection of individual biomass combustion power plants has been compared on a quantitative basis. Collected data were modified for comparison of the various power

Richard van den Broek; Ad van Wijk

1996-01-01

255

Combustion Systems for Biomass Fuel  

Microsoft Academic Search

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

Ayhan Demirbas

2007-01-01

256

Modified aspirated internal combustion engine  

Microsoft Academic Search

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

1993-01-01

257

Computer experiment on aqueous solution. IV. Molecular dynamics calculation on the hydration of urea in an infinitely dilute aqueous solution with a new urea-water pair potential  

NASA Astrophysics Data System (ADS)

A molecular dynamics calculation on aqueous solution of urea has been carried out using constant temperature technique. The total number of molecules was 216, one of which was urea and the temperature was set to 298.15 K and an experimental value was used for the density. For water-water interaction, the MCY (Matsuoka-Clementi-Yoshimine) potential was used, whereas a new potential function was determined for urea-water interaction from SCF LCAO calculations for more than 800 different dimeric configurations with an STO-3G basis set and subsequent multiparameter fitting of the MO results thus obtained to an appropriate functional form by a nonlinear optimization method. The molecular dynamics calculation has been carried out up to 64 000 time steps and from the final 40 000 time steps, thermodynamic quantities, structural and energetic distribution functions, and time-dependent properties were obtained. The original water structure in the vicinity of urea molecule is slightly changed energetically by incorporation of the urea molecule. However, this energy difference is insignificant for the whole system. Instead of the possibility to form strong hydrogen bonding as estimated from the potential function, it is found that urea molecule could enter into the water structure without any appreciable distortion. This fact was confirmed by the angular dependence of any distribution function around the urea molecule. The hydrophilic region does not show a large energetic stabilization between water molecules and the system is stabilized slightly by including urea-water interaction. In contrast to this, the energy for water molecules in the hydrophobic region (above and below the plane containing urea molecule) becomes lower than that of pure water, although this region is small and water molecules cannot form a strong hydrogen bond with urea. This fact reveals that the role of each functional region, which may be either hydrophobic or hydrophilic, is similar to that of alcohol in aqueous solution, although the whole hydration structure of urea molecule is somewhat different from that of alcohol. Reflecting strong interaction of urea-water, the diffusion coefficient for shell water molecules in the vicinity of urea (within 5 Å from urea molecule) becomes smaller by 10%. Moreover, the hydration structure around urea continues for a long time (16 ps), though the energetic relaxation time is very short.

Tanaka, H.; Touhara, Hidekazu; Nakanishi, Koichiro; Watanabe, Nobuatsu

1984-05-01

258

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

259

Molecular-dynamics simulations of urea nucleation from aqueous solution.  

PubMed

Despite its ubiquitous character and relevance in many branches of science and engineering, nucleation from solution remains elusive. In this framework, molecular simulations represent a powerful tool to provide insight into nucleation at the molecular scale. In this work, we combine theory and molecular simulations to describe urea nucleation from aqueous solution. Taking advantage of well-tempered metadynamics, we compute the free-energy change associated to the phase transition. We find that such a free-energy profile is characterized by significant finite-size effects that can, however, be accounted for. The description of the nucleation process emerging from our analysis differs from classical nucleation theory. Nucleation of crystal-like clusters is in fact preceded by large concentration fluctuations, indicating a predominant two-step process, whereby embryonic crystal nuclei emerge from dense, disordered urea clusters. Furthermore, in the early stages of nucleation, two different polymorphs are seen to compete. PMID:25492932

Salvalaglio, Matteo; Perego, Claudio; Giberti, Federico; Mazzotti, Marco; Parrinello, Michele

2015-01-01

260

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...

261

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

262

Combustion control system  

Microsoft Academic Search

A combustion control method is described for an automotive engine in a vehicle having a large, open intake manifold leading to cylinders with intake valves and exhaust valves leading to an exhaust conduit. It consists of: keeping the intake manifold wide open with no ducts and no barriers, so that all of the cylinders are joined in the large, open

Lindberg

1987-01-01

263

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

264

Asymmetrical internal combustion engine  

Microsoft Academic Search

An internal combustion engine adapted to be powered by a burnable gaseous fuel includes one cylinder, first and second pistons reciprocally movable in the cylinder substantially in opposite directions, inlet and outlet valves for controlling the flow of the gaseous fuel into the cylinder, and the exhaust of the burnt fuel therefrom, respectively, and a linkage device connected to the

Barret

1983-01-01

265

Rotary internal combustion engine  

Microsoft Academic Search

A multi bank power plant is described comprising at least a first and a second rotary internal combustion engine connectable together in series, each of the engines comprising: a housing; a cam track internally disposed within the housing and adapted to receive a cam follower; an engine block disposed within the housing and rotatable about a central axis; an output

1993-01-01

266

Reciprocating internal combustion engine  

Microsoft Academic Search

A reciprocating internal combustion engine is described having a cylinder block, a piston slidably mounted so as to travel in a cylinder bore formed in the cylinder block, a crankshaft operatively connected to the piston by a connecting rod defining a crank radius, and intake and exhaust valves. The engine comprises: a head block axially slidably mounted in the cylinder

Kamimaru

1987-01-01

267

Internal combustion engine  

Microsoft Academic Search

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

H. G. Evans; S. Speer

1991-01-01

268

Internal combustion engine  

Microsoft Academic Search

An internal combustion engine operating on a two-stroke cycle and including a piston 1 reciprocable in a cylinder 2 to drive a crank shaft and also to inhale and compress a volume of air is characterized by a second piston 15 working in a separate cylinder 13 co-axial with and opposed to the first cylinder 2, the piston 15 being

1982-01-01

269

Project Sponsors: UCI Combustion  

E-print Network

of a Commercial Microturbine Generator". 8th U. S. National Combustion Meeting. · R. Hack and V. McDonell. (2008 as predicted with the CRN model and compared to the experimental results obtained by Hack & McDonell in 2008

Mease, Kenneth D.

270

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

271

Rotary internal combustion engine  

Microsoft Academic Search

This patent describes a rotary internal combustion engine operating on fuel and air, comprising: a housing having a pair of communicating parallel axis rotor chambers; a pair of parallel axis rotors, one in each rotor chamber of the housing, the rotors each having on its outer periphery circumferentially spaced axial teeth with intervening circumferentially spaced axial passages. The rotors are

Kollen

1987-01-01

272

Downward buoyant filtration combustion  

Microsoft Academic Search

We consider heterogeneous combustion in a porous medium subject to gravity-induced buoyant forces. A vertical sample, open to flow at the top and bottom, is ignited at the top. Buoyancy causes the hot gases to leave the sample through the top, thus drawing in fresh cool gas, containing both oxidizer and inert gases, through the bottom. The incoming gas supplies

B. J. Matkowsky; D. A. Schult

1996-01-01

273

Potent Urea and Carbamate Inhibitors of Soluble Epoxide Hydrolases  

Microsoft Academic Search

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

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

1999-01-01

274

Dicyanidobis(thio­urea-?S)cadmium(II) monohydrate  

PubMed Central

In the title compound, [Cd(CN)2(CH4N2S)2]·H2O, the Cd atom lies on a twofold rotation axis and is bonded to two S atoms of thio­urea and two C atoms of the cyanide anions in a distorted tetra­hedral environment. The crystal structure is stabilized by N—H?N(CN), N—H?O, O—H?N and N—H?S hydrogen bonds. PMID:21588216

Fettouhi, Mohammed; Riaz Malik, Muhammad; Ali, Saqib; A. Isab, Anvarhusein; Ahmad, Saeed

2010-01-01

275

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

276

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

NASA Technical Reports Server (NTRS)

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

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

1980-01-01

277

A novel disposable electrochemical immunosensor for phenyl urea herbicide diuron  

Microsoft Academic Search

A disposable electrochemical immunosensor has been developed for the determination of phenyl urea herbicide-diuron using a low cost laser ablated gold electrodes (LC-LAGE) fabricated on polystyrene substrate. The electrodes were electrochemically deposited with prussian blue-gold nanoparticle (PB-GNP) film, and a competitive inhibition immunoassay was performed on LC-LAGE by using a specific hapten–protein conjugate. The binding of available diuron specific antibody

Priyanka Sharma; Kavita Sablok; Vijayender Bhalla; C. Raman Suri

2011-01-01

278

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

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

279

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

280

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

281

An epigenetic escape route.  

PubMed

Some of our fate is predetermined, by genetics and by the environment in the womb. Gestational environments are reflected in the DNA methylomes of newborns, in a manner that is often influenced by genotype. Therefore, DNA methylation serves as molecular mechanism linking the interplay of early life environments and genetics to later life health. As such, methylation marks are potential biomarkers of suboptimal developmental trajectories. Can DNA methylation also be used to construct an escape route from biological fate? PMID:25547197

Holbrook, Joanna D

2015-01-01

282

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

283

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

NASA Astrophysics Data System (ADS)

Heterostructured BiOBr/Bi24O31Br10 nanocomposites with surface oxygen vacancies are constructed by a facile in situ route of one-step self-combustion of ionic liquids. The compositions can be easily controlled by simply adjusting the fuel ratio of urea and 2-bromoethylamine hydrobromide (BTH). BTH serves not only as a fuel, but also as a complexing agent for ionic liquids and a reactant to supply the Br element. The heterojunctions show remarkable adsorptive ability for both the cationic dye of rhodamine B (RhB) and the anionic dye of methylene orange (MO) at high concentrations, which is attributed to the abundant surface oxygen vacancies. The sample containing 75.2% BiOBr and 24.8% Bi24O31Br10 exhibits the highest photocatalytic activity. Its reaction rate constant is 4.0 and 9.0 times that of pure BiOBr in degrading 50 mg L-1 of RhB and 30 mg L-1 of MO under visible-light (? > 400 nm) irradiation, respectively, which is attributed to the narrow band gap and highly efficient transfer efficiency of charge carriers. Different photocatalytic reaction processes and mechanisms over pure BiOBr and heterojunctions are proposed.Heterostructured BiOBr/Bi24O31Br10 nanocomposites with surface oxygen vacancies are constructed by a facile in situ route of one-step self-combustion of ionic liquids. The compositions can be easily controlled by simply adjusting the fuel ratio of urea and 2-bromoethylamine hydrobromide (BTH). BTH serves not only as a fuel, but also as a complexing agent for ionic liquids and a reactant to supply the Br element. The heterojunctions show remarkable adsorptive ability for both the cationic dye of rhodamine B (RhB) and the anionic dye of methylene orange (MO) at high concentrations, which is attributed to the abundant surface oxygen vacancies. The sample containing 75.2% BiOBr and 24.8% Bi24O31Br10 exhibits the highest photocatalytic activity. Its reaction rate constant is 4.0 and 9.0 times that of pure BiOBr in degrading 50 mg L-1 of RhB and 30 mg L-1 of MO under visible-light (? > 400 nm) irradiation, respectively, which is attributed to the narrow band gap and highly efficient transfer efficiency of charge carriers. Different photocatalytic reaction processes and mechanisms over pure BiOBr and heterojunctions are proposed. Electronic supplementary information (ESI) available: XRD pattern for composition calculation (Fig. S1), SEM photographs (Fig. S2), N2 absorption-desorption isotherms (Fig. S3), STEM images (Fig. S4), time-course variation of ln(C0/C) of dyes (Fig. S5), Appearance photographs for adsorption of dyes (Fig. S6), UV-Vis absorption spectra of NBT (Fig. S7), pseudo-first order rate constants for RhB and MO degradation (Tables S1 and S2), electronegativity, calculated CB and VB edge positions (Table S3). See DOI: 10.1039/c4nr05451b

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

2014-12-01

284

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

285

Dynamic features of combustion  

NASA Technical Reports Server (NTRS)

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

Oppenheim, A. K.

1985-01-01

286

THE FIRST TURBULENT COMBUSTION  

Microsoft Academic Search

The first turbulent combustion arises in a hot-big-bang cosmological model (Gibson, 2004) where nonlinear exothermic turbulence permitted by quantum mechanics, general relativity, multidimensional superstring theory, and fluid mechanics cascades from Planck to strong-force freeze-out scales with gravity balancing turbulent inertial-vortex forces. Interactions between Planck scale spinning and non-spinning black holes produce high Reynolds number turbulence and temperature mixing with huge

CARL H. GIBSON

2005-01-01

287

Combustion powered linear actuator  

SciTech Connect

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

288

Spontaneous combustion of hydrogen  

NASA Technical Reports Server (NTRS)

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

Nusselt, Wilhelm; Pothmann, PH

1923-01-01

289

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

290

The Diesel Combustion Collaboratory: Combustion Researchers Collaborating over the Internet  

SciTech Connect

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

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

2000-02-01

291

Spray combustion modeling  

NASA Technical Reports Server (NTRS)

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

Bellan, J.

1997-01-01

292

Droplet Combustion Experiment (DCE)  

NASA Technical Reports Server (NTRS)

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

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

1998-01-01

293

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.

294

Storage and flood routing  

USGS Publications Warehouse

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

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

1960-01-01

295

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

296

Design, synthesis and evaluation of non-urea inhibitors of soluble epoxide hydrolase  

PubMed Central

Inhibition of soluble epoxide hydrolase (sEH) has been proposed as a new pharmaceutical approach for treating hypertension and vascular inflammation. The most potent sEH inhibitors reported in literature to date are urea derivatives. However, these compounds have limited pharmacokinetic profiles. We investigated non-urea amide derivatives as sEH inhibitors and identified a potent human sEH inhibitor 14–34 having potency comparable to urea-based inhibitors. PMID:22079754

Pecic, Stevan; Deng, Shi-Xian; Morisseau, Christophe; Hammock, Bruce D.; Landry, Donald W.

2012-01-01

297

A general method for the solid-phase synthesis of unsymmetrical tri- and tetrasubstituted ureas.  

PubMed

A general method for the preparation of unsymmetrical di, tri-, and tetrasubstituted ureas on polymer supports is presented. Polymer-bound primary and secondary amines react with imidazolium salts (urea donors), which are generated from the reaction of N,N'-carbonyldiimidazole (CDI) with primary and secondary amines followed by alkylation with MeI to give tri- and tetrasubstituted ureas in excellent yields (76-98%) and purities (80-99%). PMID:11831880

Zheng, Changsheng; Combs, Andrew P

2002-01-01

298

On-line monitoring of urea using enzymatic field effect transistors  

Microsoft Academic Search

Silicon and polymer-based technologies were developed in order to reach the industrial fabrication of disposable, mass-fabricated microsensors for the urea detection in liquid phase. The detection principle is based on pH-sensitive chemical field effect transistor (pH-ChemFET) microdevices. In order to realize an urea-sensitive enzymatic field effect transistor (urea-EnFET), studies involve the integration of an urease-based enzymatic layer by ink jet

W. Sant; P. Temple-Boyer; E. Chanié; J. Launay; A. Martinez

299

Urease-independent chemotactic responses of Helicobacter pylori to urea, urease inhibitors, and sodium bicarbonate.  

PubMed Central

Helicobacter pylori CPY3401 and an isogenic urease-negative mutant, HPT73, showed chemotactic responses to urea, flurofamide (a potent urease inhibitor), and sodium bicarbonate. Since urea and sodium bicarbonate are secreted through the gastric epithelial surface and hydrolysis of urea by urease on the bacterial surface is essential for colonization, the chemotactic response of H. pylori may be crucial for its colonization and persistence in the stomach. PMID:9119496

Mizote, T; Yoshiyama, H; Nakazawa, T

1997-01-01

300

Flow injection analysis biosensor for urea analysis in adulterated milk using enzyme thermistor.  

PubMed

Urea in adulterated milk is one of the major health concern, it is especially harmful to pregnant women, children, and the sick. A sophisticated and reliable detection system is needed to replace current diagnostic tools for the urea in the milk. In this work, we report a flow injection analysis-enzyme thermistor (FIA-ET) bio-sensing system for monitoring of urea in adulterated milk. This biosensor was made of the covalently immobilized enzyme urease (Jack bean) on controlled pore glass (CPG) and packed into a column inside thermistor, which selectively hydrolysed the urea present in the sample. The specific heat registered from the hydrolysis of urea was found proportional to the concentration of urea present in the milk sample. The biosensor showed a linear range 1-200 mM, with % R.S.D. 0.96 for urea in 100 mM phosphate buffer, pH 7.2. Good recoveries were obtained (97.56-108.7%) for urea up to 200 mM in the spiked milk samples with % R.S.D. 0.95. In the adulterated milk, a simple filtration strategy and matrix matching technique was used to analyse urea. The response time of the sensor was evaluated for urea, which was 2 min, and it gives satisfactory output. A good comparison was observed between the urea concentrations measured through FIA-ET and the colorimetric method. These results indicate that utilizing this system could be very effective to detect low and high level of urea in adulterated milk. The immobilized urease column exhibited a good operational stability up to 180 days when used continuously at room temperature. PMID:20732804

Mishra, Geetesh K; Mishra, Rupesh K; Bhand, Sunil

2010-12-15

301

Development of a novel combustion synthesis method for synthesizing of ceramic oxide powders  

Microsoft Academic Search

A novel combustion synthesis method has been developed to prepare electronic ceramic oxide powders—Ni0.5Zn0.5Fe2O4, ZnO, LiCoO2, BaFe12O19 and YBa2Cu3O7?x (x?0.25). Organic compounds (e.g., glycine, urea, citric acid, alanine, or carbohydrazide) to be mixed directly with metal nitrates without adding water, is the key technique of this method. Metal nitrates acting as oxidants were also used as cation sources, whereas an

Chyi-Ching Hwang; Tsung-Yung Wu; Jun Wan; Jih-Sheng Tsai

2004-01-01

302

Propellant combustion at low pressures  

SciTech Connect

The combustion characteristics of a family of composite propellants have been investigated at low (i.e., subatmospheric) pressures and three different temperatures. Although a de Vieille-type burning rate law appeared to be applicable, the burning rate exponent and coefficient vary strongly with the initial temperatures. Indications are that this is primarily due to the presence of nitroguanidine and oxalate. Combustion efficiency proved to be poor. At low pressures, all propellants are susceptible to irregular burning: above 50 kPa oscillatory combustion was hardly observed. All propellants exhibit distinct preferred frequencies for oscillatory combustion. These frequencies, being much lower than the acoustic frequency of the test system, are associated with the combustion characteristics of the propellants. They depend strongly on the combustion pressure and the initial propellant temperature.

Schoyer, H.F.R.; Korting, P.A.O.G.

1986-03-01

303

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

PubMed Central

In the unicellular green alga Chlamydomonas reinhardi (strain y-1), synthesis of the enzymes required for urea hydrolysis is under substrate induction control by urea and under end product repression control by ammonia. Hydrolysis of urea if effected by the sequential action of the discrete enzymes urea carboxylase and allophanate lyase, collectively called urea amidolyase. The carboxylase converts urea to allophanate in a reaction requiring biotin, adenosine 5'-triphosphate, and Mg2+. The lyase hydrolzyes allophanate to ammonium ions and bicarbonate. Neither activity is present in more than trace amounts when cultures are grown with ammonia or urea plus ammonia, or when they are starved for nitrogen for 8 h. Urea in the absence of ammonia induces both activities 10 to 100 times the basal levels. Addition of ammonia to an induced culture causes complete cessation of carboxylase accumulation and an 80% depression of lyase accumulation. Ammonia does not reduce urea uptake by repressed cells, so it does not prevent induction by the mechanism of inducer exclusion. The unicellular green alga Chlorella pyrenoidosa (strain 3 Emerson) also has discrete carboxylase and lyase enzymes, but only the carboxylase exhibits metabolic control. PMID:1116994

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

1975-01-01

304

Limitations to carbon 13-labeled urea breath testing for Helicobacter pylori in infants.  

PubMed

We determined the validity of the carbon 13-labeled urea breath test in young children. We found that although the 13C-labeled urea breath test had a specificity greater than 90%, borderline or false positive results occurred more frequently in children younger than 2 years compared with older children. False positive results may be caused by oral-urease-producing organisms because direct intragastric administration of 13C urea reduced the excess delta 13CO2. Care is urged in interpreting one positive 13C-labeled urea breath test in children younger than 2 years. PMID:11713455

Imrie, C; Rowland, M; Bourke, B; Drumm, B

2001-11-01

305

Functional materials from self-assembled bis-urea macrocycles.  

PubMed

CONSPECTUS: This Account highlights the work from our laboratories on bis-urea macrocycles constructed from two C-shaped spacers and two urea groups. These simple molecular units assembled with high fidelity into columnar structures guided by the three-centered urea hydrogen bonding motif and aryl stacking interactions. Individual columns are aligned and closely packed together to afford functional and homogeneous microporous crystals. This approach allows for precise and rational control over the dimensions of the columnar structure simply by changing the small molecular unit. When the macrocyclic unit lacks a cavity, columnar assembly gives strong pillars. Strong pillars with external functional groups such as basic lone pairs can expand like clays to accept guests between the pillars. Macrocycles that contain sizable interior cavities assemble into porous molecular crystals with aligned, well-defined columnar pores that are accessible to gases and guests. Herein, we examine the optimal design of the macrocyclic unit that leads to columnar assembly in high fidelity and probe the feasibility of incorporating a second functional group within the macrocycles. The porous molecular crystals prepared through the self-assembly of bis-urea macrocycles display surface areas similar to zeolites but lower than MOFs. Their simple one-dimensional channels are well-suited for studying binding, investigating transport, diffusion and exchange, and monitoring the effects of encapsulation on reaction mechanism and product distribution. Guests that complement the size, shape, and polarity of the channels can be absorbed into these porous crystals with repeatable stoichiometry to form solid host-guest complexes. Heating or extraction with an organic solvent enables desorption or removal of the guest and subsequent recovery of the solid host. Further, these porous crystals can be used as containers for the selective [2 + 2] cycloadditions of small enones such as 2-cyclohexenone or 3-methyl-cyclopentenone, while larger hosts bind and facilitate the photodimerization of coumarin. When the host framework incorporates benzophenone, a triplet sensitizer, UV-irradiation in the presence of oxygen efficiently generates singlet oxygen. Complexes of this host were employed to influence the selectivity of photooxidations of 2-methyl-2-butene and cumene with singlet oxygen. Small systematic changes in the channel and bound reactants should enable systematic evaluation of the effects of channel dimensions, guest dimensions, and channel-guest interactions on the processes of absorption, diffusion, and reaction of guests within these nanochannels. Such studies could help in the development of new materials for separations, gas storage, and catalysis. PMID:24784767

Shimizu, Linda S; Salpage, Sahan R; Korous, Arthur A

2014-07-15

306

Discovery of potent, selective sulfonylfuran urea endothelial lipase inhibitors.  

PubMed

Endothelial lipase (EL) activity has been implicated in HDL catabolism, vascular inflammation, and atherogenesis, and inhibitors are therefore expected to be useful for the treatment of cardiovascular disease. Sulfonylfuran urea 1 was identified in a high-throughput screening campaign as a potent and non-selective EL inhibitor. A lead optimization effort was undertaken to improve potency and selectivity, and modifications leading to improved LPL selectivity were identified. Radiolabeling studies were undertaken to establish the mechanism of action for these inhibitors, which were ultimately demonstrated to be irreversible inhibitors. PMID:19058966

Goodman, Krista B; Bury, Michael J; Cheung, Mui; Cichy-Knight, Maria A; Dowdell, Sarah E; Dunn, Allison K; Lee, Dennis; Lieby, Jeffrey A; Moore, Michael L; Scherzer, Daryl A; Sha, Deyou; Suarez, Dominic P; Murphy, Dennis J; Harpel, Mark R; Manas, Eric S; McNulty, Dean E; Annan, Roland S; Matico, Rosalie E; Schwartz, Benjamin K; Trill, John J; Sweitzer, Thomas D; Wang, Da-Yuan; Keller, Paul M; Krawiec, John A; Jaye, Michael C

2009-01-01

307

Structure oftheTetragonal Surface Layerof Sporosarcina ureae  

Microsoft Academic Search

structure oftheregular surface layer ofSporosarcina ureae hasbeendetermined to aresolution of1.7nmbyelectron microscopy andimage reconstruction. TheS-layer hasp4symmetry, alattice constant of12.9nm,andaminimumthickness of6.6nm.Thereconstruction reveals adistinct domain structure: amassive core, armsconnecting adjacent unit cells, andspurs whichmakecontact atthesubsidiary fourfold symmetry axes. Inthez-direction thedomains appear tobearranged inthree planes, creating two entirely different surface reliefs. TheS-layer hasacomplex pattern ofpores andgapsthat are2to3nmwide. Inaddition, thesecondary-structure composition hasbeendetermined byinfrared spectroscopy: about

HARALD ENGELHARDT; W. OWEN SAXTON; ANDWOLFGANG BAUMEISTER

1986-01-01

308

DYNAMIC ROUTES THROUGH VIRTUAL PATHS ROUTING FOR AD HOC NETWORKS  

E-print Network

DYNAMIC ROUTES THROUGH VIRTUAL PATHS ROUTING FOR AD HOC NETWORKS Abdulrahman H. Altalhi Golden G and selected based on multiple criteria. The rest of this paper is organized as follows. In Section 2, we describe, in a high level, the design and operations of the VPR protocol. In Section 3, we detail

Richard III, Golden G.

309

Composite propellant combustion modeling studies  

NASA Technical Reports Server (NTRS)

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

Ramohalli, K.

1977-01-01

310

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

311

Combustion transfer in gasless pyrotechnics  

SciTech Connect

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

Boddington, T.; Cottrell, A.; Laye, P.G. (Leeds Univ. (UK))

1990-03-01

312

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 private-sector organizations that may be able to utilize these materials in the conduct of their missions should also provide input. The CBRC will serve as an effective vehicle for acquiring and maintaining guidance from these diverse organizations so that the proper balance in the R&D program is achieved.

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

2008-08-31

313

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

314

Rotary internal combustion engine  

SciTech Connect

This patent describes a rotary internal combustion engine operating on fuel and air, comprising: a housing having a pair of communicating parallel axis rotor chambers; a pair of parallel axis rotors, one in each rotor chamber of the housing, the rotors each having on its outer periphery circumferentially spaced axial teeth with intervening circumferentially spaced axial passages. The rotors are positioned with the teeth and passages of one rotor engaging, respectively, the passages and teeth of the other rotor, and each of the rotors further having an internal chamber surrounding axial generally cylindrical oblique helicoid walls forming a mixer means; mean for introducing a mixture of the fuel and air into the mixer chambers of the rotors whereby rotating of the rotors correspondingly rotates and mixer means to homogenize the mixture to produce a fuel/air mist; means for transferring the mist from the mixer chambers to a predetermined injection point in the rotor chambers of the housing such that the mist is disposed in selected passages of the rotors as the selected passages rotate past the predetermined injection point; means for igniting the mist at a predetermined ignition point in the rotor chambers of the housing. The predetermined ignition point is proximate a combustion chamber formed by interengagement of the teeth of the rotors immediately adjacent the selected passages. Exhaust resulting from ignition of the mist urges expansion of the combustion chamber and causes rotation of the rotors; and means for extracting the exhaust as the selected passages rotate past a predetermined exhaust point in the rotor chambers of the housing. The predetermined exhaust point is located in the rotor chambers such that the selected passages of the rotors rotate past the predetermined exhaust point before rotating past the predetermined injection point.

Kollen, R.H.

1987-01-06

315

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

316

Combustion of White Phosphorus  

NASA Astrophysics Data System (ADS)

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

Keiter, Richard L.; Gamage, Chaminda P.

2001-07-01

317

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

318

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 is focused on spray physics and associated combustion instability phenomena. Results concerning high pressure droplet gasification model, droplet turbulent dispersion model, and spray atomization model will contribute to the development of new computational tools for design of stable liquid propellant rocket engines.

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

1989-01-01

319

Breaking Up with Combustion  

NSDL National Science Digital Library

This activity teaches combustion as the interaction of a fuel source and oxygen. A burning candle is observed, then extinguished—first by a glass cup placed over it to cut off the oxygen supply, then using carbon dioxide generated by vinegar and baking soda. Some background information is provided about how car engines use gasoline as fuel, and how humans use food as fuel— both are similar to how the candle uses wax as fuel. The activity is written for a kit that can be checked out of the library, but the kit is not required.

2012-06-26

320

Container for combustible  

SciTech Connect

A combustible pack comprising a hollow cardboard container divided by a bent strip of cardboard 28 into an upper compartment and a generally triangular lower compartment 30 and having a central flue 42 through the upper compartment and communicating with the lower compartment. An ignitor 44 is provided in the lower compartment and charcoal or the like is provided in the upper compartment on each side of the flue. The flue is formed by a cardboard strip 32 that is bent to extend between the top wall of the container and the dividing strip 28.

Kalil, D.G.; Deeb, D.J.; Kalil, G.T.

1984-07-17

321

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

322

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

323

Platelet adhesion to polyurethane urea under pulsatile flow conditions.  

PubMed

Platelet adhesion to a polyurethane urea surface is a precursor to thrombus formation within blood-contacting cardiovascular devices, and platelets have been found to adhere strongly to polyurethane surfaces below a shear rate of approximately 500?s(-1) . The aim of the current work is to determine the properties of platelet adhesion to the polyurethane urea surface as a function of time-varying shear exposure. A rotating disk system was used to study the influence of steady and pulsatile flow conditions (e.g., cardiac inflow and sawtooth waveforms) for platelet adhesion to the biomaterial surface. All experiments were conducted with the same root mean square angular rotation velocity (29.63?rad/s) and waveform period. The disk was rotated in platelet-rich bovine plasma for 2?h, with adhesion quantified by confocal microscopy measurements of immunofluorescently labeled bovine platelets. Platelet adhesion under pulsating flow was found to decay exponentially with increasing shear rate. Adhesion levels were found to depend upon peak platelet flux and shear rate, regardless of rotational waveform. In combination with flow measurements, these results may be useful for predicting regions susceptible to thrombus formation within ventricular assist devices. PMID:24721222

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

2014-12-01

324

Automated monosegmented flow analyser. Determination of glucose, creatinine and urea.  

PubMed

An automated monosegmented flow analyser containing a sampling valve and a reagent addition module and employing a laboratory-made photodiode array spectrophotometer as detection system is described. The instrument was controlled by a 386SX IBM compatible microcomputer through an IC8255 parallel port that communicates with the interface which controls the sampling valve and reagent addition module. The spectrophotometer was controlled by the same microcomputer through an RS232 serial standard interface. The software for the instrument was written in QuickBasic 4.5. Opto-switches were employed to detect the air bubbles limiting the monosegment, allowing precise sample localisation for reagent addition and signal reading. The main characteristics of the analyser are low reagent consumption and high sensitivity which is independent of the sample volume. The instrument was designed to determine glucose, creatinine or urea in blood plasma and serum without hardware modification. The results were compared against those obtained by the Clinical Hospital of UNICAMP using commercial analysers. Correlation coefficients among the methods were 0.997, 0.982 and 0.996 for glucose, creatinine and urea, respectively. PMID:9463952

Raimundo Júnior, I M; Pasquini, C

1997-10-01

325

Influence of excipients on moisturizing effect of urea.  

PubMed

Water is the most important molecule contained in the skin and is bound to the intracellular hygroscopic substances called natural moisturizing factors (NMF). The clinical characteristic of xerosis is rough and/or coarse skin. This anaesthetic alteration necessitates cosmetic products application. In this study, we tested the efficiency of urea incorporated into six different emulsions (O/W) and 10 different gels. Skin of 10 healthy women (20 to 45 years) was treated using 50 mg of emulsion or gel containing 5% of urea. A skin surface of 16 cm(2) was chosen in the area of the forearm. The gain in moisturizing was performed measuring the skin electrical capacity using a corneometer (Courage & Khazaka, model CM 825), one hour after treatment. Sodium carboxymethyl cellulose gel has the least moisturizing effect. On the other hand, the mixture of polyacrylamide and C13-14 isoparaffin polysorbate 85 can be a good vehicle in the treatment of skin dehydration. Adding various oils (6%) or collagen in aqueous solution does not improve the efficiency of the tested products. Moisturizing effect of gels (polyacrylamine with C13-14 isoparaffin polysorbate 85) is higher than the one of emulsions (L/H). PMID:16537204

Couteau, C; Coiffard, L J M; Sébille-Rivain, V

2006-02-01

326

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...

327

Plasma igniter for internal-combustion engines  

NASA Technical Reports Server (NTRS)

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

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

1978-01-01

328

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

NASA Astrophysics Data System (ADS)

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

Berne, B. J.

2009-03-01

329

Isotope-labelled urea to test colon drug delivery devices in vivo: principles, calculations and interpretations.  

PubMed

This paper describes various methodological aspects that were encountered during the development of a system to monitor the in vivo behaviour of a newly developed colon delivery device that enables oral drug treatment of inflammatory bowel diseases. [(13)C]urea was chosen as the marker substance. Release of [(13)C]urea in the ileocolonic region is proven by the exhalation of (13)CO2 in breath due to bacterial fermentation of [(13)C]urea. The (13)CO2 exhalation kinetics allows the calculation of a lag time as marker for delay of release, a pulse time as marker for the speed of drug release and the fraction of the dose that is fermented. To determine the total bioavailability, also the fraction of the dose absorbed from the intestine must be quantified. Initially, this was done by calculating the time-dependent [(13)C]urea appearance in the body urea pool via measurement of (13)C abundance and concentration of plasma urea. Thereafter, a new methodology was successfully developed to obtain the bioavailability data by measurement of the urinary excretion rate of [(13)C]urea. These techniques required two experimental days, one to test the coated device, another to test the uncoated device to obtain reference values for the situation that 100 % of [(13)C]urea is absorbed. This is hampered by large day-to-day variations in urea metabolism. Finally, a completely non-invasive, one-day test was worked out based on a dual isotope approach applying a simultaneous administration of [(13)C]urea in a coated device and [(15)N2]urea in an uncoated device. All aspects of isotope-related analytical methodologies and required calculation and correction systems are described. PMID:24313370

Maurer, Marina J M; Schellekens, Reinout C A; Wutzke, Klaus D; Stellaard, Frans

2013-01-01

330

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

331

[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

332

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

PubMed

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

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

2015-03-01

333

Computing shortest heterochromatic monotone routes  

Microsoft Academic Search

Abstract. Given a set of n points on the plane colored with k • n colors, the Trip Planning Problem asks for the shortest path visiting the k colors. It is a well-known NP-hard problem. We show that under some natural constraints on the path, the problem can be solved in polynomial time. Keywords: Routing; Heterochromatic Monotone Route; Shortest Path;

José Miguel Díaz-báñez; G. Hernández; D. Oliveros; A. Ramírez-vigueras; Joan Antoni Sellarès; Jorge Urrutia; Inmaculada Ventura

2008-01-01

334

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

335

Capacity Allocation Under Noncooperative Routing  

Microsoft Academic Search

The capacity allocation problem in a network that is to be shared by noncooperative users is considered. Each user decides independently upon its routing strategy so as to optimize its individual performance objective. The operating points of the network are the Nash equilibria of the underlying routing game. The network designer aims to allocate link capacities, so that the resulting

Yannis A. Korilis; Aurel A. Lazar; Ariel Orda

1995-01-01

336

Anonymous connections and onion routing  

Microsoft Academic Search

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

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

1998-01-01

337

Producing Gestures Facilitates Route Learning  

PubMed Central

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

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

2014-01-01

338

How Bad is Selfish Routing?  

Microsoft Academic Search

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

Tim Roughgarden; Eva Tardost

2000-01-01

339

Oak Ridge via State Route  

E-print Network

PLANT EAST TENNESSEE TECHNOLOGY PARK (FORMERLY K-25 PLANT) OAK RIDGE NATIONAL LABORATORY (X-10)1 2 SNSKnoxville Nashville Oak Ridge via State Route 162 North OAK RIDGE INN & SUITES THE RIDGE INN. TRANSFER SNS PROJECT OFFICE COMMERCE PARK OAK RIDGE/KNOXVILLE ROUTE MAP A B C D E F G H I J K L M N O P Q R

Pennycook, Steve

340

Simulation of Ships' Routing System  

Microsoft Academic Search

This paper describes a well-designed and calibrated simulation model to solve the design of Ships' routeing system which provide useful insights about complex maritime transportation routes. Real data from shanghai port Vessel Traffic Services Center (VTS) are used as input for evaluating four traffic policies. The simulation model mainly focuses on the transit traffic in the channel. This study provides

Xiao Ying Jie; Zhang Hao

2010-01-01

341

Some Factors Affecting Combustion in an Internal-Combustion Engine  

NASA Technical Reports Server (NTRS)

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

Rothrock, A M; Cohn, Mildred

1936-01-01

342

An Architecture-oriented Routing Method for FPGAs Having Rich Hierarchical Routing Resources  

Microsoft Academic Search

We have developed an architecture-oriented routing method for a telecommunications FPGA (Field-Programmable Gate Array) which has rich hierarchical routing resources. Our routing method consists of four routing procedures, each of which are related to a specific part of the routing resource architecture of the FPGA. It can accomplish routing results almost five times faster than a reference method that does

Takahiro Murooka; Atsushi Takahara; Toshiaki Miyazaki; Akihiro Tsutsui

1998-01-01

343

An adaptive control strategy for urea-SCR aftertreatment system  

Microsoft Academic Search

Hydrocarbons, carbon monoxide, and other polluting emissions produced by diesel engines are usually much lower than those from gasoline engines. However, higher combustion temperature in diesel engines cause substantially larger percentage of nitrogen oxides (NOx) emissions. Selective catalyst reduction (SCR) is a well proven technology for reducing NOx emissions from automotive sources and in particular, heavy-duty truck diesel engines. In

Mona Meisami-Azad; Javad Mohammadpour; Karolos M. Grigoriadis; Michael P. Harold

2010-01-01

344

A novel DHT Routing Protocol for MANETs  

E-print Network

The central challenge in Mobile Ad hoc Networks (MANETs) is to provide a stable routing strategy without depending on any central administration. This work presents and examines the working of Radio Ring Routing Protocol (RRRP), a DHT based routing...

Chellamani, Deepak

2010-04-30

345

46 CFR 45.175 - Applicable routes.  

Code of Federal Regulations, 2013 CFR

...LINES GREAT LAKES LOAD LINES Unmanned River Barges on Lake Michigan Routes § 45.175 Applicable routes. This subpart...the following routes, including intermediate ports, on Lake Michigan, between Calumet Harbor, IL, and— (a) Milwaukee,...

2013-10-01

346

46 CFR 45.175 - Applicable routes.  

Code of Federal Regulations, 2010 CFR

...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 Lake Michigan, between Chicago (Calumet Harbor), IL, and— (a)...

2010-10-01

347

46 CFR 45.175 - Applicable routes.  

Code of Federal Regulations, 2012 CFR

...LINES GREAT LAKES LOAD LINES Unmanned River Barges on Lake Michigan Routes § 45.175 Applicable routes. This subpart...the following routes, including intermediate ports, on Lake Michigan, between Calumet Harbor, IL, and— (a) Milwaukee,...

2012-10-01

348

46 CFR 45.175 - Applicable routes.  

Code of Federal Regulations, 2011 CFR

...LINES GREAT LAKES LOAD LINES Unmanned River Barges on Lake Michigan Routes § 45.175 Applicable routes. This subpart...the following routes, including intermediate ports, on Lake Michigan, between Calumet Harbor, IL, and— (a) Milwaukee,...

2011-10-01

349

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

350

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

PubMed

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

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

2012-01-01

351

Utilization ROLE OF COAL COMBUSTION  

E-print Network

. These include fly ash, bottom ash, boiler slag, and flue gas desulfurization (FGD) products from pulverized coal combustion products (CCPs)" [1]. These include fly ash, bottom ash, boiler slag, and flue gas desulfurization, materials left after combustion of coal in conventional and/ or advanced clean-coal technology combustors

Wisconsin-Milwaukee, University of

352

Muffler for internal combustion engines  

Microsoft Academic Search

A muffler is described for an internal combustion engine comprising: (a) an outer box composed of separated bodies made of a formed sound insulation material and having portions joined by an adhesive, the outer box having an inlet for introducing an exhaust gas from the internal combustion engine and an outlet for discharging the exhaust gas; (b) a reinforcing member

T. Inoue; H. Saito; T. Takewaka; H. Funabashi

1986-01-01

353

Piston for internal combustion engine  

Microsoft Academic Search

This patent describes a piston for an internal combustion engine comprising: (a) a piston main body made of a first material and having an opening in a top surface thereof, the opening having an upper large diameter portion and a lower small diameter portion with a shoulder defined therebetween; (b) a cavity forming member having a combustion chamber cavity formed

H. Nagase; A. Umemoto

1986-01-01

354

Internal combustion engine control system  

Microsoft Academic Search

This patent describes an internal combustion engine control system comprising: A detector which measures the quantity of intake air and quantity of fuel supply as a control value reflecting the operational state of an internal combustion engine; An air-fuel ratio control which determines, based on the measured controlled variable, a base control value used for controlling the other controlled variable;

M. Kiyono; T. Abe; M. Takao

1989-01-01

355

Liquid propellant rocket combustion instability  

NASA Technical Reports Server (NTRS)

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

Harrje, D. T.

1972-01-01

356

Tetra-aqua-bis-(thio-urea-?S)cadmium(II) triaqua-tris(thio-urea-?S)cadmium(II) disulfate.  

PubMed

The title compound, [Cd(CH(4)N(2)S)(2)(H(2)O)(4)][Cd(CH(4)N(2)S)(3)(H(2)O)(3)](SO(4))(2), contains two mol-ecules of each of the Cd complexes and four sulfate ions in the asymmetric unit: all the Cd atoms exhibit distorted octa-hedral geometries. The Cd-S and Cd-O bond lengths around the Cd atoms in the bis-(thio-urea) cations are in the ranges 2.580?(4)-2.599?(4) and 2.323?(8)-2.421?(9)?Å, respectively, and the S atoms are in a cis orientation. In the tris-(thio-urea) cations, the corresponding bond lengths around the Cd atoms are slightly longer and are in the ranges 2.559?(4)-2.706?(3) and 2.303?(7)-2.480?(10)?Å, respectively, and the S atoms are in a fac disposition. The crystal structure features numerous N-H?O, N-H?N, O-H?O and O-H?N hydrogen bonds. Two O atoms of a sulfate anion were found to be disordered over two orientations in a 0.620?(9):0.380?(9) ratio. The crystal studied was a racemic twin with BASF = 0.17?(5). PMID:22807774

Parvez, Masood; Jalilehvand, Farideh; Amini, Zahra

2012-07-01

357

Solubility Measurement and Modelling of Urea in Supercritical CO2 and CO2 + Ethanol Mixtures  

Microsoft Academic Search

The solubility of urea in supercritical CO2 and CO2 + ethanol was measured over the pressure and temperature ranges 100 - 300 bar and 313 - 373 K respectively, and ethanol concentrations 0 - 25 % by mass (urea free basis). The solubility in CO2 was measured by a once-through packed bed gravimetric method at a laboratory and pilot scale.

O. J. Catchpole; S. J. Tallon; P. J. Dyer; J.-S. Lan; B. Jensen; O. K. Rasmussen

358

High Affinity Carboxylate Binding Using Neutral Urea-Based Receptors with  

E-print Network

High Affinity Carboxylate Binding Using Neutral Urea-Based Receptors with Internal Lewis Acid to date have employed either Lewis acid-base,3 hydrogen bond- ing,4 and/or ion-dipole interactions.5 Most binding ability of neutral urea-based receptors. It is likely that this strategy can be incorporated

Smith, Bradley D.

359

Availability of banded triple superphosphate with urea and phosphorus use efficiency by corn  

Microsoft Academic Search

Phosphorus fixation results in low P use efficiency in acid soils. Increase in soil pH through urea hydrolysis may improve P availability and use efficiency. Growth chamber and field experiments were conducted to evaluate effects of urea on triple superphosphate (TSP) transformation and P use efficiency. A Ste. Rosalie clay (Typic Humaquept), an Ormstown silty clay loam (Typic Humaquept) and

D. S. Ouyang; A. F. MacKenzie; M. X. Fan

1999-01-01

360

Mitigation of Ammonia Loss from Urea Applied to Moist Soils by Agrotain  

E-print Network

Mitigation of Ammonia Loss from Urea Applied to Moist Soils by Agrotain® Richard Engel and Clain). In Fertilizer Fact Sheet 59 we reported that ammonia (NH3) losses from cold soils (e.g. as the soil dried, a worst-case scenario for NH3 loss. Methods Ammonia losses from urea and Agrotain® treated

Lawrence, Rick L.

361

Nitrogen digestion and urea recycling in Hokkaido native horses fed hay-based diets.  

PubMed

Nitrogen (N) digestion and urea-N metabolism in Hokkaido native horses fed roughage-based diets containing different types and levels of protein sources were studied. Horses (173?±?4.8?kg) fitted with an ileum cannula were fed four diets consisting of 100% timothy hay (TH), 88% TH and 12% soybean meal (SBM), 79% TH and 21% SBM, and 51% TH and 49% alfalfa hay at 2.2% of body weight. Dietary protein content varied from 5% to 15% of dry matter. Apparent N digestibilities in the pre-cecum and total tract for the TH diet were lower than those for other diets. However, the proportion of post-ileum N digestion to N intake was not affected by the diets. Urea-N production was linearly related to N intake, but gut urea-N entry was not affected by the diets. The proportion of gut urea-N entry to urea-N production tended to be higher for the TH diet (57%) than the two SBM diets (39%). Anabolic use of urea-N entering the gut was not affected by the diets (20-36% of gut urea-N entry). These results indicate that urea-N recycling provides additional N sources for microbial fermentation in the hindgut of Hokkaido native horses fed low-quality roughages. PMID:25040128

Obitsu, Taketo; Hata, Hiroshi; Taniguchi, Kohzo

2015-02-01

362

Urea Metal-Organic Frameworks as Effective and Size-Selective Hydrogen-Bond Catalysts  

E-print Network

Supporting Information ABSTRACT: A new urea-containing metal-organic frame- work (MOF) was synthesized to act as a heterogeneous catalyst. Ureas are well-known for self-recognition and aggrega- tion behavior, resulting in loss collective interests in MOFs and catalysis, we have developed a collaborative program aimed at merging metal

363

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...

364

Urea and Ammonia Metabolism and the Control of Renal Nitrogen Excretion.  

PubMed

Renal nitrogen metabolism primarily involves urea and ammonia metabolism, and is essential to normal health. Urea is the largest circulating pool of nitrogen, excluding nitrogen in circulating proteins, and its production changes in parallel to the degradation of dietary and endogenous proteins. In addition to serving as a way to excrete nitrogen, urea transport, mediated through specific urea transport proteins, mediates a central role in the urine concentrating mechanism. Renal ammonia excretion, although often considered only in the context of acid-base homeostasis, accounts for approximately 10% of total renal nitrogen excretion under basal conditions, but can increase substantially in a variety of clinical conditions. Because renal ammonia metabolism requires intrarenal ammoniagenesis from glutamine, changes in factors regulating renal ammonia metabolism can have important effects on glutamine in addition to nitrogen balance. This review covers aspects of protein metabolism and the control of the two major molecules involved in renal nitrogen excretion: urea and ammonia. Both urea and ammonia transport can be altered by glucocorticoids and hypokalemia, two conditions that also affect protein metabolism. Clinical conditions associated with altered urine concentrating ability or water homeostasis can result in changes in urea excretion and urea transporters. Clinical conditions associated with altered ammonia excretion can have important effects on nitrogen balance. PMID:25078422

Weiner, I David; Mitch, William E; Sands, Jeff M

2014-07-30

365

Urea as a protein destabilizing agent in electrospray Lynda J. Donald1*, Vladimir M. Collado2  

E-print Network

; Accepted 8 January 2009 Urea is well known as a denaturant of proteins, but there is also evidence stable), and higher charge states if the proteins were denatured. We have found that mM urea interferes alcohol,5 can produce an increase in the charge state of a given protein. It is generally accepted

O'Neil, Joe

366

75 FR 51055 - Propionic Acid and Salts, and Urea Sulfate; Registration Review Proposed Decisions; Notice of...  

Federal Register 2010, 2011, 2012, 2013, 2014

...EPA-HQ-OPP-2010-0650; FRL-8840-5] Propionic Acid and Salts, and Urea Sulfate; Registration Review...decisions for the pesticides propionic acid and salts, and urea sulfate and opens a public comment...pesticide formulations. Propionic acid and its salts, sodium and calcium propionates,...

2010-08-18

367

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

368

Origins of Protein Denatured State Compactness and Hydrophobic Clustering in Aqueous Urea: Inferences from  

E-print Network

Origins of Protein Denatured State Compactness and Hydrophobic Clustering in Aqueous Urea capacity signature ( CP) of a compact denatured state can be similar to CP values calculated by assuming: hydrophobicity; urea denaturation; sol- vent accessible surface area; compact denatured states; m-value; heat

Shimizu, Seishi

369

Coating of Prilled Urea with Neem (Azadirachta Indica Juss) Oil for Efficient Nitrogen Use in Rice  

NASA Astrophysics Data System (ADS)

A field study made with rice at the Indian Agricultural Research Institute, New Delhi, showed that coating urea with neem oil, neem cake or neem oil microemulsion improved rice growth and resulted in more grain and straw than did commercial prilled urea.

Prasad, R.; Singh, S.; Saxena, V. S.; Devkumar, C.

370

Wheat cultivated with organic fertilizers and urea: Baking performance and dough properties  

Microsoft Academic Search

Data describing white flour composition, dough properties and baking performance of both spring and winter wheat treated with different fertilizer strategies including meat bone meal, slurry manure and urea, were analyzed by principal component analysis and variance analysis. No significant differences in the analyzed variables were found between flour from wheat fertilized with organic fertilizers or urea at different N

Helena Fredriksson; Lennart Salomonsson

1997-01-01

371

Morphological and functional characteristics of the kidney of cartilaginous fishes: with special reference to urea reabsorption.  

PubMed

For adaptation to high-salinity marine environments, cartilaginous fishes (sharks, skates, rays, and chimaeras) adopt a unique urea-based osmoregulation strategy. Their kidneys reabsorb nearly all filtered urea from the primary urine, and this is an essential component of urea retention in their body fluid. Anatomical investigations have revealed the extraordinarily elaborate nephron system in the kidney of cartilaginous fishes, e.g., the four-loop configuration of each nephron, the occurrence of distinct sinus and bundle zones, and the sac-like peritubular sheath in the bundle zone, in which the nephron segments are arranged in a countercurrent fashion. These anatomical and morphological characteristics have been considered to be important for urea reabsorption; however, a mechanism for urea reabsorption is still largely unknown. This review focuses on recent progress in the identification and mapping of various pumps, channels, and transporters on the nephron segments in the kidney of cartilaginous fishes. The molecules include urea transporters, Na(+)/K(+)-ATPase, Na(+)-K(+)-Cl(-) cotransporters, and aquaporins, which most probably all contribute to the urea reabsorption process. Although research is still in progress, a possible model for urea reabsorption in the kidney of cartilaginous fishes is discussed based on the anatomical features of nephron segments and vascular systems and on the results of molecular mapping. The molecular anatomical approach thus provides a powerful tool for understanding the physiological processes that take place in the highly elaborate kidney of cartilaginous fishes. PMID:25339681

Hyodo, Susumu; Kakumura, Keigo; Takagi, Wataru; Hasegawa, Kumi; Yamaguchi, Yoko

2014-12-15

372

The fate of labelled 15 N urea and ammonium nitrate applied to a winter wheat crop  

Microsoft Academic Search

Labelled urea or ammonium nitrate was applied to winter wheat growing on a loamy soil in Northern France. Two applications of fertilizer were given: 50 kg N ha?1 at tillering (early March) and 110 kg N ha?1 at the beginning of stem elongation (mid-April). The kinetics of urea hydrolysis, nitrification of ammonium and the disappearance of inorganic nitrogen were followed

S. Recous; C. Fresneau; G. Faurie; B. Mary

1988-01-01

373

Microbial protein production determined by urinary allantoin and renal urea sparing in normal  

E-print Network

Short note Microbial protein production determined by urinary allantoin and renal urea sparing. Renal functional tests for urea handling studies, and determination of urinary allantoin as an indirect of allantoin, thereby leading to an underestimation of the amount of microbial protein entering in the duodenum

Paris-Sud XI, Université de

374

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

375

A retrospective survey of the use of laboratory tests to simulate internal combustion engine materials tribology problems  

Microsoft Academic Search

Progress in the Field of tribology strongly parallels, and has always been strongly driven by, developments and needs in transportation and related industries. Testing of candidate materials for internal combustion engine applications has historically taken several routes: (1) replacement of parts in actual engines subjected to daily use, (2) testing in special, instrumented test engines, (3) and simulative testing in

Blau

1992-01-01

376

Urea breath test for Helicobacter pylori detection: present status.  

PubMed

Helicobacter pylori (H. pylori) is the commonest bacterial pathogen found worldwide and more than half the world population aged 40 years and above is colonized with it. The infection rate is >95 % in some African countries. In 1994, the International Agency for Research on cancer classified H. pylori as a class I carcinogen in humans. It causes chronic active gastritis, duodenal and gastric ulcer and gastric malignancy, and is thought to be associated with coronary artery disease, cerebral stroke, vitamin B12 and iron-deficiency anaemia, etc. Therefore, non-invasive test-and-treatment strategies are widely recommended in primary care settings. Conventionally, H. pylori infection can be diagnosed by invasive techniques using an upper gastrointestinal endoscope for obtaining multiple biopsies from different sites of the stomach for RUT, culture, histological examination, polymerase chain reaction (PCR), etc. and by non-invasive tests such as Urea breath test (UBT), stool antigen test and blood serology. At present, 13/14C-UBT is considered the test of choice for confirmation of H. pylori infection. The UBT is based on the principle, that isotopically labelled urea ingested by an H. pylori--infected patient is rapidly hydrolysed by the microbial urease. The released 13/14CO2 is absorbed across the mucous layer to the gastric mucosa and hence, excreted via the systemic circulation in the breath which is collected and measured. The non-hydrolysed urea is excreted completely in the urine within 3-4 days. 13C-UBT being non-radioactive, 13C-UBT can be used in pregnant women and children, and a user's license is not required. There is still no standard protocol accepted and followed internationally for this test. Although the methods are almost similar, various laboratories/clinics use variable tracer doses, test meals, timings and methods for breath collection, and different cut-off values, which make formal validation studies necessary. This review describes the present status of the UBT and its application in the detection of H. pylori infection. PMID:15912972

Pathak, C M; Bhasin, D K; Khanduja, K L

2004-01-01

377

EFFECT OF FOLIAR APPLICATION OF UREA, MOLYBDENUM, BENZYLADENINE, SUCROSE AND SALICYLIC ACID ON YIELD, NITROGEN METABOLISM OF RADISH PLANTS AND QUALITY OF EDIBLE ROOTS  

Microsoft Academic Search

In 2006–2007 small radish was cultivated in a pot experiment. Foliar applications were applied twice with solutions of the following compounds: 1) control (water); 2) urea; 3) urea+molybdenum (Mo), 4) urea+Mo+benzyladenine (BA); 5) urea+Mo+BA+sucrose; 6) urea+Mo+BA+sucrose+salicylic acid (SA), 7) BA; 8) SA; and 9) sucrose. The above solutions contained following concentrations of compounds: urea 20 g dm, sucrose 10 g

Sylwester Smole?; W?odzimierz Sady

2012-01-01

378

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

379

Forensic utility of isotope ratio analysis of the explosive urea nitrate and its precursors.  

PubMed

Urea nitrate (UN) is an improvised explosive made from readily available materials. The carbon and nitrogen isotope composition of UN and its component ions, urea and nitrate, could aid in a forensic investigation. A method was developed to separate UN into its component ions for ?(15)N measurements by dissolving the sample with KOH, drying the sample, followed by removal of the urea by dissolution into 100% methanol. UN was synthesized to assess for preservation of the carbon and nitrogen isotope compositions of reactants (urea and nitric acid) and product UN. Based on nitrogen isotope mass balance, all UN samples contained varying amounts of excess nitric acid, making the ionic separation an essential step in the nitrogen isotope analysis. During UN synthesis experiments, isotopic composition of the reactants is preserved in the product UN, but the urea in the product UN is slightly enriched in (15)N (<1‰) relative to the reactant urea. Published isotopic compositions of UN reactants, urea and nitric acid, have large ranges (urea ?(15)N = -10.8 to +3.3‰; urea ?(13)C = -18.2 to -50.6‰; and nitric acid ?(15)N = -1.8 to +4.0‰). The preservation of isotopic composition of reactants in UN, along with a significant variability in isotopic composition of reactants, indicates that isotope ratio analysis may be used to test if urea or nitric acid collected during an investigation is a possible reactant for a specific UN sample. The carbon and nitrogen isotope ratios differ significantly between two field-collected UN samples, as well as the lab-synthesized UN samples. These observed variations suggest that this approach is useful for discriminating between materials which are otherwise chemically identical. PMID:20729019

Aranda, Roman; Stern, Libby A; Dietz, Marianne E; McCormick, Meghan C; Barrow, Jason A; Mothershead, Robert F

2011-03-20

380

Potent Urea and Carbamate Inhibitors of Soluble Epoxide Hydrolases  

NASA Astrophysics Data System (ADS)

The soluble epoxide hydrolase (sEH) plays a significant role in the biosynthesis of inflammation mediators as well as xenobiotic transformations. Herein, we report the discovery of substituted ureas and carbamates as potent inhibitors of sEH. Some of these selective, competitive tightbinding inhibitors with nanomolar Ki values interacted stoichiometrically with the homogenous recombinant murine and human sEHs. These inhibitors enhance cytotoxicity of trans-stilbene oxide, which is active as the epoxide, but reduce cytotoxicity of leukotoxin, which is activated by epoxide hydrolase to its toxic diol. They also reduce toxicity of leukotoxin in vivo in mice and prevent symptoms suggestive of acute respiratory distress syndrome. These potent inhibitors may be valuable tools for testing hypotheses of involvement of diol and epoxide lipids in chemical mediation in vitro or in vivo systems.

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

1999-08-01

381

Combustion of viscous hydrocarbons  

SciTech Connect

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

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

1987-08-04

382

Rotary internal combustion engine  

SciTech Connect

A rotary internal combustion engine having a housing defining a chamber is disclosed. A fixed shaft extends coaxially through the chamber. A plurality of vanes are pinned to a collar which is rotative about the shaft. One vane is rigidly secured to the collar. A cylindrical drum is positioned in the working chamber with the centerline of the drum radially offset from the centerline of the working chamber. The vanes extend through slots or apertures in the rotor to close proximity with the chamber wall. A fuel delivery system communicates with the chamber through approximately 90 degrees of the compression cycle. An exhaust opening communicates with the chamber at the end of the expansion cycle whereby the compression ratio is substantially less than the expansion ratio. In one embodiment means are provided to vary the compression and expansion ratios.

Crutchfield, M.R.

1980-12-30

383

Combustion in porous media  

SciTech Connect

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

Dillon, J. [California Inst. of Technology, CA (US)

1999-09-01

384

Application of selective non-catalytic reduction of NO x in small-scale combustion systems  

NASA Astrophysics Data System (ADS)

The selective non-catalytic reduction of NO x has been studied experimentally employing commercial grade urea in a pilot-scale diesel-fired tunnel furnace at 3-4% excess oxygen level and with low ppm of baseline NO x ranging from 65 to 75 ppm within the investigated temperature range. The furnace simulated the thermal behavior of small-scale combustion systems such as small capacity boilers, water heaters, oil heaters, etc., where the operating temperatures remain within the range of 950-1300 K. NO x reductions were studied with the variation of injection temperature, residence time, normalized stoichiometric ratio (NSR) of the reagent, etc. With 5% urea solution, at an NSR of 4, as much as 54% reduction was achieved at 1128 K. The result is quite significant, especially for the investigated level of baseline NO x. The ammonia slip measurements showed that the slip was below 16 ppm at NSR of 4 and optimum temperature of NO x reduction. Finally, the investigations have demonstrated that selective non-catalytic reduction process is quite applicable to the small-scale combustion applications.

Abul Hossain, Khandoker; Nazri Mohd Jaafar, Mohammad; Mustafa, Azeman; Babu Appalanidu, Kiran; Nasir Ani, Farid

385

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

386

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

387

Ventilation effects on combustion products.  

PubMed

The effects of fire ventilation on combustion products are expressed in terms of relationship between concentration of products and equivalence ratio, phi. For well-ventilated fires, phi < 1.0, where mostly heat and products of complete combustion (such as CO2 and water) are generated. For ventilation-controlled fires, phi > 1.0, where mostly products of incomplete combustion are generated with very high concentrations in a transition region for phi between 1.0 and 3.5. The high concentrations of the products of incomplete combustion are dangerous to life and property. For halogenated materials, this condition occurs for phi < 1.0. The non-flaming region for fires is found to exist for phi > 3.5. Correlations have been developed for the prediction of concentrations of products at various phi values for the assessment of combustion toxicity and smoke damage hazards by zone fire models, such as Hazard 1. The correlations show good agreement with the measured concentrations. The concentrations of the products of incomplete combustion depend on the chemical structures of the materials. For the same phi values, the carbon monoxide concentrations are higher for materials with oxygen atoms in the structure, whereas smoke concentrations are higher for materials with carbon and hydrogen atoms in the structure. The results of the study suggest that it is necessary to examine the combustion behaviour of advanced materials for use in aircraft and other critical applications at various phi values, along with the toxicity experiments. PMID:9016749

Tewarson, A

1996-12-31

388

Ammonia and urea treatment of wheat straw and corn stover JP Fontenot E Gallo Llorente, JM Obamahinti, VG Allen  

E-print Network

Ammonia and urea treatment of wheat straw and corn stover JP Fontenot E Gallo Llorente, JM, with ammonia and urea on nutritional value for ruminants. For each crop residue, square bales were allotted to three treatments : 1 - No treatment (control), 2 - Ammonia treatment, and 3 - Urea treat- ment. Jackbean

Boyer, Edmond

389

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

Federal Register 2010, 2011, 2012, 2013, 2014

...FRL-8836-6] Petitions Concerning Whether Ammonia or Urea Sold or Distributed and Used for...concerning petitions concerning whether ammonia or urea sold or distributed and used for...comment on petitions concerning whether ammonia or urea sold or distributed and used...

2010-07-14

390

What is Milk Urea Nitrogen and How is It Interpreted? Dr. Doo-Hong Min, Extension Forage Specialist, MSU UPES  

E-print Network

What is Milk Urea Nitrogen and How is It Interpreted? Dr. Doo-Hong Min, Extension Forage Specialist, MSU UPES Milk urea nitrogen (MUN) is another tool to assess the protein and energy balance status of a group of dairy cows and can be used for minimizing feed costs while maximizing production. Milk urea

391

Postprandial increases in nitrogenous excretion and urea synthesis in the giant mudskipper Periophthalmodon schlosseri.  

PubMed

The objective of this study was to determine the effects of feeding on the excretory nitrogen (N) metabolism of the giant mudskipper, Periophthalmodon schlosseri, with special emphasis on the role of urea synthesis in ammonia detoxification. The ammonia and urea excretion rates of P. schlosseri increased 1.70- and 1.92-fold, respectively, within the first 3 h after feeding on guppies. Simultaneously, there were significant decreases in ammonia levels in the plasma and the brain, and in urea contents in the muscle and liver, of P. schlosseri at 3 h post-feeding. Thus, it can be concluded that P. schlosseri was capable of unloading ammonia originally present in some of its tissues in anticipation of ammonia released from the catabolism of excess amino acids after feeding. Subsequently, there were significant increases in urea content in the muscle, liver and plasma (1.39-, 2.17- and 1.62-fold, respectively) at 6 h post-feeding, and the rate of urea synthesis apparently increased 5.8-fold between 3 h and 6 h. Increased urea synthesis might have occurred in the liver of P. schlosseri because the greatest increase in urea content was observed therein. The excess urea accumulated in the body at 6 h was completely excreted between 6 and 12 h, and the percentage of waste-N excreted as urea-N increased significantly to 26% during this period, but never exceeded 50%, the criterion for ureotely, meaning that P. schlosseri remained ammonotelic after feeding. By 24 h, 62.7% of the N ingested by P. schlosseri was excreted, out of which 22.6% was excreted as urea-N. This is the first report on the involvement of increased urea synthesis and excretion in defense against ammonia toxicity in the giant mudskipper, and our results suggest that an ample supply of energy resources, e.g. after feeding, is a prerequisite for the induction of urea synthesis. Together, increases in nitrogenous excretion and urea synthesis after feeding effectively prevented a postprandial surge of ammonia in the plasma of P. schlosseri as reported previously for other fish species. Consequently, contrary to previous reports, there were significant decreases in the ammonia content of the brain of P. schlosseri throughout the 24 h period post-feeding, accompanied by a significant decrease in brain glutamine content between 12 h and 24 h. PMID:15277556

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

2004-08-01

392

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

393

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

394

Regulation possibilities of biomass combustion  

NASA Astrophysics Data System (ADS)

The focus of the recent experimental research is to analyze the regulation possibilities of biomass combustion. Three possibilities were chosen as part of this research: a) biomass cofiring with propane, b) swirling flow with re-circulation zone, and c) use of a permanent magnet. The aim of the research is to provide stable, controllable and effective biomass combustion with minimum emissions. The special pilot device was created where biomass can be combusted separately and co-fired with propane. Wood pellets were used during the experiments.

Suzdalenko, Vera; Gedrovics, Martins; Zake, Maija; Barmina, Inesa

2012-11-01

395

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

396

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

397

Smouldering Combustion Phenomena in Science and Technology  

Microsoft Academic Search

Smouldering is the slow, low-temperature, flameless form of combustion of a condensed fuel. It poses safety and environmental hazards and allows novel technological application but its fundamentals remain mostly unknown to the scientific community. The terms filtering combustion, smoking problem, deep seated fires, hidden fires, peat or peatlands fires, lagging fires, low oxygen combustion, in-situ combustion, fireflood and underground gasification,

Guillermo Rein

398

Chemical-looping combustion – a thermodynamic study  

Microsoft Academic Search

The poor performance of internal combustion (IC) engines can be attributed to the departure from equilibrium in the combustion process. This departure is expressed numerically, as the difference between the working fluid's temperature and an ideal 'combustion tempera- ture', calculated using a simple expression. It is shown that for combustion of hydrocarbons to be performed reversibly in a single reaction,

N R McGlashan

2008-01-01

399

Combustion kinetics of sewage sludge and combustible wastes  

Microsoft Academic Search

This study estimated the kinetics of the mono- and co-combustion of sewage sludge pellets and combustible wastes such as municipal\\u000a solid waste (MSW) and refuse-derived fuel (RDF). Sewage sludge was manufactured into pellets with a diameter of 8, 12, or\\u000a 16 mm and a length of 30 mm. The RDF was composed of paper and plastics and was formed into

Ho-Soo Lee; Sung-Keun Bae

2009-01-01

400

Anonymous Connections and Onion Routing  

Microsoft Academic Search

Onion Routing provides anonymous connections that are strongly resistant to both eavesdropping and tra c analysis. Unmodi ed Internet applications can use these anonymous connections by means of prox-ies. The proxies may also make communication anony-mous by removing identifying information from the data stream. Onion routing has been implemented on Sun Solaris 2.X with proxies for Web browsing, remote logins,

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

1997-01-01

401

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

402

A disposable biosensor for urea determination in blood based on an ammonium-sensitive transducer.  

PubMed

A potentiometric urea-sensitive biosensor using a NH4(+)-sensitive disposable electrode in double matrix membrane (DMM) technology as transducer is described. The ion-sensitive polymer matrix membrane was formed in the presence of an additional electrochemical inert filter paper matrix to improve the reproducibility in sensor production. The electrodes were prepared from one-side silver-coated filter paper, which is encapsulated for insulation by a heat-sealing film. A defined volume of the NH4(+)-sensitive polymer matrix membrane cocktail was deposited on this filter paper. To obtain the urea-biosensor a layer of urease was cast onto the ion-sensitive membrane. Poly (carbamoylsulfonate) hydrogel, produced from a hydrophilic polyurethane prepolymer blocked with bisulfite, served as immobilisation material. The disposable urea sensitive electrode was combined with a disposable Ag/AgCl reference electrode to obtain the disposable urea biosensor. The sensor responded rapidly and in a stable manner to changes in urea concentrations between 7.2 x 10(-5) and 2.1 x 10(-2)mol/l. The detection limit was 2 x 10(-5) mol/l urea and the slope in the linear range 52 mV/decade. By taking into consideration the influence of the interfering K(+)- and Na(+)-ions the sensor can be used for the determination of urea in human blood and serum samples (diluted or undiluted). A good correlation was found with the data obtained by the spectrophotometric routine method. PMID:10028647

Eggenstein, C; Borchardt, M; Diekmann, C; Gründig, B; Dumschat, C; Cammann, K; Knoll, M; Spener, F

1999-01-01

403

Low protein diet alters urea transport and cell structure in rat initial inner medullary collecting duct.  

PubMed Central

Low protein diets reverse the urea concentration gradient in the renal inner medulla. To investigate the mechanism(s) for this change, we studied urea transport and cell ultrastructure in initial and terminal inner medullary collecting ducts (IMCD) from rats fed 18% protein or an isocaloric, 8% protein diet for 4 wk. Serum urea, aldosterone, and albumin were significantly lower in rats fed 8% protein, but total protein and potassium were unchanged. Vasopressin stimulated passive urea permeability (Purea) threefold (P < 0.05) in initial IMCDs from rats fed 8% protein, but not from rats fed 18% protein. Luminal phloretin reversibly inhibited vasopressin-stimulated Purea. However, in terminal IMCDs from rats fed either diet, vasopressin stimulated Purea. Net transepithelial urea flux (measured with identical perfusate and bath solutions) was found only in initial IMCDs from rats fed 8% protein. Reducing the temperature reversibly inhibited it, but phloretin did not. Electron microscopy of initial IMCD principal cells from rats fed 8% protein showed expanded Golgi bodies and prominent autophagic vacuoles, and morphometric analysis demonstrated a marked increase in the surface density and boundary length of the basolateral plasma membrane. These ultrastructural changes were not observed in the terminal IMCD. Thus, 8% dietary protein causes two new urea transport processes to appear in initial but not terminal IMCDs. This is the first demonstration that "active" urea transport can be induced in a mammalian collecting duct segment. Images PMID:8227360

Isozaki, T; Verlander, J W; Sands, J M

1993-01-01

404

Multicommodity Flow Algorithms for Buffered Global Routing  

E-print Network

Multicommodity Flow Algorithms for Buffered Global Routing Christoph Albrecht, Andrew B. Kahng, Ion on a multicommodity flow formulation for the buffered global routing problem. Multicommodity flow based global routing to be a distinct advantage of multicommodity flow based methods over all other approaches to global routing

Zelikovsky, Alexander

405

THE VEHICLE ROUTING PROBLEM WITH STOCHASTIC DEMANDS  

Microsoft Academic Search

The standard Vehicle Routing Problem model usually needs to be extended in order to solve real- world vehicle routing problems. A stochastic vehicle routing model is suitable for real world situation. In many routing situation, elements such as demand quantities are a nonnegative random variable with a known probability distribution. Actual demands are revealed only upon the visit to a

Ayhan Karahan; Tufan Demirel; Nihan Çetin Demirel

406

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

407

Energy metabolism, body composition, and urea generation rate in hemodialysis patients.  

PubMed

Hemodialysis (HD) adequacy is currently assessed using normalized urea clearance (Kt/V), although scaling based on Watson volume (V) may disadvantage women and men with low body weight. Alternative scaling factors such as resting energy expenditure and high metabolic rate organ mass have been suggested. The relationship between such factors and uremic toxin generation has not been established. We aimed to study the relationship between body size, energy metabolism, and urea generation rate. A cross-sectional cohort of 166 HD patients was studied. Anthropometric measurements were carried on all. Resting energy expenditure was measured by indirect calorimetry, fat-free mass by bio-impedance and total energy expenditure by combining resting energy expenditure with a questionnaire-derived physical activity data. High metabolic rate organ mass was calculated using a published equation and urea generation rate using formal urea kinetic modeling. Metabolic factors including resting energy expenditure, total energy expenditure and fat-free mass correlated better with urea generation rate than did Watson volume. Total energy expenditure and fat-free mass (but not Watson Volume) were independent predictors of urea generation rate, the model explaining 42% of its variation. Small women (urea generation rate per kg than women with higher V. Similarly urea generation rate normalized to fat-free mass was significantly greater in small women than in all others (significant only in comparison to larger men). Exercise-related energy expenditure correlated significantly with urea generation rate. Energy metabolism, body composition and physical activity play important roles in small solute uremic toxin generation in HD patients and hence may impact on minimum dialysis requirements. Small women generate relatively more small solute toxins than other groups and thus may have a higher relative need for dialysis. PMID:23480424

Sridharan, Sivakumar; Vilar, Enric; Berdeprado, Jocelyn; Farrington, Ken

2013-10-01

408

Thermal stabilization of catalyst supports and their application to high-temperature catalytic combustion  

Microsoft Academic Search

Recent studies concerning thermal stabilization of catalyst supports and their application to a catalytic gas turbine combustor were reviewed. Development of heat-resistant catalysts has received considerable attention for the development of high-tempearture combustion catalysts. The use of additives such as La, Si, Ba, etc., is a promising way to improve the thermal stability of alumina-based support materials. Preparation routes also

Hiromichi Arai; Masato Machida

1996-01-01

409

High Efficiency, Clean Combustion  

SciTech Connect

Energy use in trucks has been increasing at a faster rate than that of automobiles within the U.S. transportation sector. According to the Energy Information Administration (EIA) Annual Energy Outlook (AEO), a 23% increase in fuel consumption for the U.S. heavy duty truck segment is expected between 2009 to 2020. The heavy duty vehicle oil consumption is projected to grow between 2009 and 2050 while light duty vehicle (LDV) fuel consumption will eventually experience a decrease. By 2050, the oil consumption rate by LDVs is anticipated to decrease below 2009 levels due to CAFE standards and biofuel use. In contrast, the heavy duty oil consumption rate is anticipated to double. The increasing trend in oil consumption for heavy trucks is linked to the vitality, security, and growth of the U.S. economy. An essential part of a stable and vibrant U.S. economy is a productive U.S. trucking industry. Studies have shown that the U.S. gross domestic product (GDP) is strongly correlated to freight transport. Over 90% of all U.S. freight tonnage is transported by diesel power and over 75% is transported by trucks. Given the vital role that the trucking industry plays in the economy, improving the efficiency of the transportation of goods was a central focus of the Cummins High Efficient Clean Combustion (HECC) program. In a commercial vehicle, the diesel engine remains the largest source of fuel efficiency loss, but remains the greatest opportunity for fuel efficiency improvements. In addition to reducing oil consumption and the dependency on foreign oil, this project will mitigate the impact on the environment by meeting US EPA 2010 emissions regulations. Innovation is a key element in sustaining a U.S. trucking industry that is competitive in global markets. Unlike passenger vehicles, the trucking industry cannot simply downsize the vehicle and still transport the freight with improved efficiency. The truck manufacturing and supporting industries are faced with numerous challenges to reduce oil consumption and greenhouse gases, meet stringent emissions regulations, provide customer value, and improve safety. The HECC program successfully reduced engine fuel consumption and greenhouse gases while providing greater customer valve. The US EPA 2010 emissions standard poses a significant challenge for developing clean diesel powertrains that meet the DoE Vehicle Technologies Multi-Year Program Plan (MYPP) for fuel efficiency improvement while remaining affordable. Along with exhaust emissions, an emphasis on heavy duty vehicle fuel efficiency is being driven by increased energy costs as well as the potential regulation of greenhouse gases. An important element of the success of meeting emissions while significantly improving efficiency is leveraging Cummins component technologies such as fuel injection equipment, aftertreatment, turbomahcinery, electronic controls, and combustion systems. Innovation in component technology coupled with system integration is enabling Cummins to move forward with the development of high efficiency clean diesel products with a long term goal of reaching a 55% peak brake thermal efficiency for the engine plus aftertreatment system. The first step in developing high efficiency clean products has been supported by the DoE co-sponsored HECC program. The objectives of the HECC program are: (1) To design and develop advanced diesel engine architectures capable of achieving US EPA 2010 emission regulations while improving the brake thermal efficiency by 10% compared to the baseline (a state of the art 2007 production diesel engine). (2) To design and develop components and subsystems (fuel systems, air handling, controls, etc) to enable construction and development of multi-cylinder engines. (3) To perform an assessment of the commercial viability of the newly developed engine technology. (4) To specify fuel properties conducive to improvements in emissions, reliability, and fuel efficiency for engines using high-efficiency clean combustion (HECC) technologies. To demonstrate the technology is compatible with B2

Donald Stanton

2010-03-31

410

75 FR 32142 - Combustible Dust  

Federal Register 2010, 2011, 2012, 2013, 2014

...interested parties to participate in a Web Chat on the workplace hazards of combustible dust. OSHA plans to use the information gathered in response to this Web Chat...Director, OSHA Office of Communications, Room N-3647,...

2010-06-07

411

Fifth International Microgravity Combustion Workshop  

NASA Technical Reports Server (NTRS)

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

Sacksteder, Kurt (Compiler)

1999-01-01

412

Combustion modeling in waste tanks  

SciTech Connect

This paper has two objectives. The first one is to repeat previous simulations of release and combustion of flammable gases in tank SY-101 at the Hanford reservation with the recently developed code GASFLOW-II. The GASFLOW-II results are compared with the results obtained with the HMS/TRAC code and show good agreement, especially for non-combustion cases. For combustion GASFLOW-II predicts a steeper pressure rise than HMS/TRAC. The second objective is to describe a so-called induction parameter model which was developed and implemented into GASFLOW-II and reassess previous calculations of Bureau of Mines experiments for hydrogen-air combustion. The pressure time history improves compared with the one-step model, and the time rate of pressure change is much closer to the experimental data.

Mueller, C.; Unal, C. [Los Alamos National Lab., NM (United States); Travis, J.R. [Los Alamos National Lab., NM (United States)]|[Forschungszentrum Karlsruhe (Germany). Inst. fuer Reaktorsicherheit

1997-08-01

413

Sixth International Microgravity Combustion Workshop  

NASA Technical Reports Server (NTRS)

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

Sacksteder, Kurt (Compiler)

2001-01-01

414

CONVENTIONAL COMBUSTION ENVIRONMENTAL ASSESSMENT PROGRAM  

EPA Science Inventory

The brochure gives a generic overview of EPA's Conventional Combustion Environmental Assessment (CCEA) Program. The CCEA Program was established recently to coordinate and integrate EPA's research and development efforts for assessing the environmental effects of pollutants from ...

415

75 FR 10739 - Combustible Dust  

Federal Register 2010, 2011, 2012, 2013, 2014

...Materials that may form combustible dust include, but are not limited to, wood, coal, plastics, biosolids, candy, sugar, spice, starch, flour, feed, grain, fertilizer, tobacco, paper, soap, rubber, drugs, dried blood, dyes, certain...

2010-03-09

416

75 FR 3881 - Combustible Dust  

Federal Register 2010, 2011, 2012, 2013, 2014

...Materials that may form combustible dust include, but are not limited to, wood, coal, plastics, biosolids, candy, sugar, spice, starch, flour, feed, grain, fertilizer, tobacco, paper, soap, rubber, drugs, dried blood, dyes, certain...

2010-01-25

417

Predictive modeling of combustion processes  

E-print Network

Recently, there has been an increasing interest in improving the efficiency and lowering the emissions from operating combustors, e.g. internal combustion (IC) engines and gas turbines. Different fuels, additives etc. are ...

Sharma, Sandeep, Ph. D. Massachusetts Institute of Technology

2009-01-01

418

Flameless Combustion for Gas Turbines  

NASA Astrophysics Data System (ADS)

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

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

2006-11-01

419

Loop-bed combustion apparatus  

DOEpatents

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

Shang, Jer-Yu (Fairfax, VA); Mei, Joseph S. (Morgantown, WV); Slagle, Frank D. (Kingwood, WV); Notestein, John E. (Morgantown, WV)

1984-01-01

420

Four Lectures on Turbulent Combustion  

E-print Network

.8 Derivation of an Equation for the Mean Progress Variable . . . . 51 3 Non-Premixed Turbulent Combustion 57 3 the nozzle until it stabilizes at a distance, called the lift-off height downstream of the nozzle. Pa

Peters, Norbert

421

Reducing mode circulating fluid bed combustion  

DOEpatents

A method for combustion of sulfur-containing fuel in a circulating fluid bed combustion system wherein the fuel is burned in a primary combustion zone under reducing conditions and sulfur captured as alkaline sulfide. The reducing gas formed is oxidized to combustion gas which is then separated from solids containing alkaline sulfide. The separated solids are then oxidized and recycled to the primary combustion zone.

Lin, Yung-Yi (Katy, TX); Sadhukhan, Pasupati (Katy, TX); Fraley, Lowell D. (Sugarland, TX); Hsiao, Keh-Hsien (Houston, TX)

1986-01-01

422

Digital image processing of coal stream combustion  

E-print Network

spacing. Thus interactions exist amongst the particles for dense clouds. While the earlier literature dealt with combustion processes of isolated particles, the recent research focusses upon the interactive combustion. The interactive combustion studies... include arrays consisting of a finite number of particles, and streams and clouds of a large number of particles. Particularly stream combustion models assume cylindrical geometry and predict the ignition and combustion characteristics. The models show...

Gopalakrishnan, Chengappalli Periyasamy

1994-01-01

423

Reverse microemulsion synthesis of nanostructured complex oxides for catalytic combustion  

PubMed

Catalysts play an important role in many industrial processes, but their use in high-temperature applications-such as energy generation through natural gas combustion, steam reforming and the partial oxidation of hydrocarbons to produce feedstock chemicals--is problematic. The need for catalytic materials that remain stable and active over long periods at high operation temperatures, often in the presence of deactivating or even poisoning compounds, presents a challenge. For example, catalytic methane combustion, which generates power with reduced greenhouse-gas and nitrogen-oxide emissions, is limited by the availability of catalysts that are sufficiently active at low temperatures for start-up and are then able to sustain activity and mechanical integrity at flame temperatures as high as 1,300 degrees C. Here we use sol-gel processing in reverse microemulsions to produce discrete barium hexa-aluminate nanoparticles that display excellent methane combustion activity, owing to their high surface area, high thermal stability and the ultrahigh dispersion of cerium oxide on the their surfaces. Our synthesis method provides a general route to the production of a wide range of thermally stable nanostructured composite materials with large surface-to-volume ratios and an ultrahigh component dispersion that gives rise to synergistic chemical and electronic effects, thus paving the way to the development of catalysts suitable for high-temperature industrial applications. PMID:10638751

Zarur; Ying

2000-01-01

424

An alternative explanation for the collapse of unfolded proteins in an aqueous mixture of urea and guanidinium chloride  

NASA Astrophysics Data System (ADS)

Molecular dynamics simulations have shown that a totally unfolded protein in aqueous 8 M urea undergoes a collapse transition on replacing urea molecules by guanidinium chloride, GdmCl, assuming a compact conformation in 4 M urea + 4 M GdmCl [J. Am. Chem. Soc. 134 (2012) 18266]. This is unexpected because GdmCl is a denaturant stronger than urea. It is shown that such collapse can originate from an increase in the magnitude of the solvent-excluded volume effect due the high density of urea + GdmCl mixtures, coupled to their low water number density that pushes denaturant molecules toward the protein surface.

Graziano, Giuseppe

2014-09-01

425

Smoldering Combustion Experiments in Microgravity  

NASA Technical Reports Server (NTRS)

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

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

1997-01-01

426

Vertical combustor for refuse combustion  

Microsoft Academic Search

A vertical combustor for refuse-particle combustion was analyzed for waste-to-energy recovery. A one-dimensional model was constructed that consisted of fuel particles, inert solid particles, and the gaseous mixture. The gaseous mixture was divided further into six chemical species that are involved in combustion at temperatures below about 2000°F. It was concluded that such combustors may be viable in the United

Chung

1981-01-01

427

Modelling paradigms for MILD combustion  

E-print Network

, CB2 1PZ, UK. E-mail: ns341@cam.ac.uk. Phone: +44(0)1223 332586. Fax: +44(0)1223 339906. Running Title: Modelling of MILD combustion Submitted to International Journal of Advances in Engineering Sciences and Applied Mathematics (Special Issue... Modelling paradigms for MILD combustion Y. Minamoto and N. Swaminathan? Department of Engineering, Cambridge University, Cambridge, CB2 1PZ, UK. ?Corresponding author: Department of Engineering, Cambridge University, Trumpington Street, Cambridge...

Minamoto, Y.; Swaminathan, N.

2014-04-26

428

Laser applications to combustion research  

Microsoft Academic Search

Measurement techniques and the range of applications of several laser-based methods for performing combustion research are reviewed. Scattered laser light speckle metrology can be used to quantify in-plane vibration, translation, rotation, and strain in combustion engine-powered systems. Laser velocimetry permits high frequency measurements of both the particle size and velocity in a flowfield, as well as the turbulence intensity, correlations,

A. K. Gupta

1983-01-01

429

Hierarchical Modeling of Combustion Processes  

Microsoft Academic Search

\\u000a Combustion processes are governed by a strong coupling of chemical kinetics, molecular transport processes and flow. Mathematical\\u000a modeling is complicated by the existence of scaling problems (time-, velocity- and length scales). In order to allow a reliable\\u000a numerical simulation of practical combustion systems, models have to be devised which do not neglect or over-simplify the\\u000a underlying physical and chemical processes.

Ulrich Maas; Viatcheslav Bykov; Andriy Rybakov; Rainer Stauch

430

Lean premixed/prevaporized combustion  

NASA Technical Reports Server (NTRS)

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

Lefebvre, A. H. (editor)

1977-01-01

431

Route Fragility: A Novel Metric for Route Selection in Mobile Ad Hoc Networks  

E-print Network

Route Fragility: A Novel Metric for Route Selection in Mobile Ad Hoc Networks Omesh Tickoo, Satish dynamic route lasts longer, we propose a new metric, the Route Fragility Coefficient (RFC), to compare that lower the value of RFC, more static (less fragile) the route. We then use this metric as a basis

Kalyanaraman, Shivkumar

432

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

E-print Network

in both experiments were fed a molasses mixture containing 93. 5f. molasses (79. 5 Brix), go water, 0 2' urea (45/o Nitrogen) and 0. 5' salt (NaC1) free choice. In the first experiment 12 heifers were divided into two groups of six and assigned... the high roughage group). Both groups had access ad libitum to a mixture of molasses-urea containing 93 ' 5g molasses, + water, 2' urea and 0. 5' salt, and received a protein supplement (fish meal) at a rate of 120 g per 100 kg body weight per day...

Pina, Angel Modesto

2012-06-07

433

Determination of urea in serum by a fiber-optic fluorescence biosensor.  

PubMed

A new fiber-optic biosensor for urea has been developed, based on immobilized urease coupled to a fluorescence ammonia sensor. The enzymatically generated ammonia diffuses through the membrane into a solution of the fluorescent pH indicator trisodium 8-hydroxypyrene-1,3,6-trisulfonate. The sensor has been successfully used for the determination of urea in serum samples, with results in good agreement with those reported by a local hospital. The proposed sensor is reversible and selective to urea. The ease of construction of the sensor tip offers the possibility of designing disposable tips for use in clinical applications. PMID:18965284

Xie, X; Suleiman, A A; Guilbault, G G

1991-10-01

434

The permeability of red blood cells to chloride, urea and water.  

PubMed

This study extends permeability (P) data on chloride, urea and water in red blood cells (RBC), and concludes that the urea transporter (UT-B) does not transport water. P of chick, duck, Amphiuma means, dog and human RBC to (36)Cl(-), (14)C-urea and (3)H2O was determined under self-exchange conditions. At 25°C and pH 7.2-7.5, PCl is 0.94 × 10(-4)-2.15 × 10(-4) cm s(-1) for all RBC species at [Cl]=127-150 mmol l(-1). In chick and duck RBC, P(urea) is 0.84 × 10(-6) and 1.65 × 10(-6) cm s(-1), respectively, at [urea]=1-500 mmol l(-1). In Amphiuma, dog and human RBC, P(urea) is concentration dependent (1-1000 mmol l(-1), Michaelis-Menten-like kinetics; K1/2;=127, 173 and 345 mmol l(-1)), and values at [urea]=1 mmol l(-1) are 29.5 × 10(-6), 467 × 10(-6) and 260 × 10(-6) cm s(-1), respectively. Diffusional water permeability, Pd, was 0.84 × 10(-3) (chick), 5.95 × 10(-3) (duck), 0.39 × 10(-3) (Amphiuma), 3.13 × 10(-3) (dog) and 2.35 × 10(-3) cm s(-1) (human). DIDS, DNDS and phloretin inhibit PCl by >99% in all RBC species. PCMBS, PCMB and phloretin inhibit P(urea) by >99% in Amphiuma, dog and human RBC, but not in chick and duck RBC. PCMBS and PCMB inhibit Pd in duck, dog and human RBC, but not in chick and Amphiuma RBC. Temperature dependence, as measured by apparent activation energy, EA, of PCl is 117.8 (duck), 74.9 (Amphiuma) and 89.6 kJ mol(-1) (dog). The EA of P(urea) is 69.6 (duck) and 53.3 kJ mol(-1) (Amphiuma), and that of Pd is 34.9 (duck) and 32.1 kJ mol(-1) (Amphiuma). The present and previous RBC studies indicate that anion (AE1), urea (UT-B) and water (AQP1) transporters only transport chloride (all species), water (duck, dog, human) and urea (Amphiuma, dog, human), respectively. Water does not share UT-B with urea, and the solute transport is not coupled under physiological conditions. PMID:23470663

Brahm, Jesper

2013-06-15

435

Pulse enhanced fluidized bed combustion  

SciTech Connect

Various technologies are available for the combustion of high-sulfur, high-ash fuels, particularly coal. From performance, economic and environmental standpoints, fluidized bed combustion (FBC) is the leading candidate for utilization of high sulfur coals. ThermoChem, Inc., and the South Carolina Energy Research and Development Center (SCERDC) are installing a hybrid fluidized bed combustion system at Clemson University. This hybrid system, known as the Pulsed Atmospheric Fluidized Bed Combustor (PAFBC), will augment the University`s steam system by providing 50--60,000 lbs/hr of saturated process steam. The PAFBC, developed by Manufacturing and Technology Conversion International, Inc., (MTCI), integrates a pulse combustor with a bubbling-bed-type atmospheric fluidized bed coal combustor. The pulse combustion system imparts an acoustic effect that enhances combustion efficiency, SO{sub 2} capture, low NO{sub x} emissions, and heat transfer efficiency in the fluidized bed. These benefits of pulse combustion result in modestly sized PAFBC units with high throughput rates and lower costs when compared to conventional fluidized bed units.

Mueller, B.; Golan, L. [South Carolina Energy Research and Development Center, Clemson, SC (United States); Toma, M.; Mansour, M. [Manufacturing and Technology Conversion International, Inc., Columbia, MD (United States)

1996-12-31

436

Fluid bed combustion: Lessons learned  

SciTech Connect

With increasing frequency, fluid bed combustion (FBC) is mentioned as the technology selected in new waste-to-energy plants. There has, however, been relatively little action. Experience in applying this technology to refuse combustion in the U.S. is confined to one operating plant; and the facility, in Duluth, Minn., uses bubbling bed reactors, not FBC boilers. One other U.S. plant hs been shut down. Facilities planned or under construction in Erie, Pa., Petersburg, VA., and Galveston County, Tex., are slated to use FBC technology. Despite this lack of experience with municipal waste, fluid bed combustion has a long history. It has been used successfully for over 25 years in sewage sludge combustion, industrial waste combustion, and, in recent years, in coal-fired boilers. With this background it seems curious that not much progress is being made in applying FBC to municipal solid waste. What does fluid bed combustion have to offer. Proponents say the technology can decrease emissions and reduce ash disposal problems. What follows is an overview of what has been accomplished, in real terms, in full-size commercial plants designed and built to burn MSW in fluid beds.

Kleinau, J.H.

1988-04-01

437

Catalytic combustion with steam injection  

NASA Technical Reports Server (NTRS)

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

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

1982-01-01

438

Aerovalve pulse combustion: Technical note  

SciTech Connect

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

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

1994-07-01

439

EMISSIONS ASSESSMENT OF CONVENTIONAL STATIONARY COMBUSTION SYSTEMS: VOLUME V: INDUSTRIAL COMBUSTION SOURCES  

EPA Science Inventory

The report characterizes air emissions from industrial external combustion sources and is the last of a series of five reports characterizing emissions from conventional combustion sources. The emissions characterization of industrial combustion sources was based on a critical ex...

440

MECHANISM AND KINETICS OF THE FORMATION OF NOX AND OTHER COMBUSTION POLLUTANTS. PHASE I. UNMODIFIED COMBUSTION  

EPA Science Inventory

The report gives Phase I results of an investigation of the mechanisms and kinetics of the formation of NOx and other combustion pollutants. It gives results of experimental investigations of unmodified combustion and supporting theoretical calculations. The combustion of hydroge...

441

NASA Microgravity Combustion Science Program  

NASA Technical Reports Server (NTRS)

Combustion has been a subject of increasingly vigorous scientific research for over a century, not surprising considering that combustion accounts for approximately 85% of the world's energy production and is a key element of many critical technologies used by contemporary society. Although combustion technology is vital to our standard of living, it also poses great challenges to maintaining a habitable environment. A major goal of combustion research is production of fundamental (foundational) knowledge that can be used in developing accurate simulations of complex combustion processes, replacing current "cut-and-try" approaches and allowing developers to improve the efficiency of combustion devices, to reduce the production of harmful emissions, and to reduce the incidence of accidental uncontrolled combustion. With full understanding of the physics and chemistry involved in a given combustion process, including details of the unit processes and their interactions, physically accurate models which can then be used for parametric exploration of new combustion domains via computer simulation can be developed, with possible resultant definition of radically different approaches to accomplishment of various combustion goals. Effects of gravitational forces on earth impede combustion studies more than they impede most other areas of science. The effects of buoyancy are so ubiquitous that we often do not appreciate the enormous negative impact that they have had on the rational development of combustion science. Microgravity offers potential for major gains in combustion science understanding in that it offers unique capability to establish the flow environment rather than having it dominated by uncontrollable (under normal gravity) buoyancy effects and, through this control, to extend the range of test conditions that can be studied. It cannot be emphasized too strongly that our program is dedicated to taking advantage of microgravity to untangle complications caused by gravity, allowing major strides in our understanding of combustion processes and in subsequent development of improved combustion devices leading to improved quality of life on Earth. Fire and/or explosion events aboard spacecraft could be devastating to international efforts to expand the human presence in space. Testing to date has shown that ignition and flame spread on fuel surfaces (e.g., paper, wire insulation) behave quite differently under partial gravity and microgravity conditions. In addition, fire signatures-i.e., heat release, smoke production, flame visibility, and radiation-are now known to be quite different in reduced gravity environments; this research has provided data to improve the effectiveness of fire prevention practices, smoke and fire detectors, and fire extinguishment systems. The more we can apply our scientific and technological understanding to potential fire behavior in microgravity and partial gravity, the more assurance can be given to those people whose lives depend on the environment aboard spacecraft or eventually on habitats on the Moon or Mars.

King, Merrill K.

1999-01-01

442

Combustion control system  

SciTech Connect

A combustion control method is described for an automotive engine in a vehicle having a large, open intake manifold leading to cylinders with intake valves and exhaust valves leading to an exhaust conduit. It consists of: keeping the intake manifold wide open with no ducts and no barriers, so that all of the cylinders are joined in the large, open intake manifold, supplying fuel to the intake manifold, withdrawing a sidestream of gas from the exhaust gas, cooling the sidestream to below water condensation temperature, removing the condensed water from the cooled sidestream, creating a whirling tornado-like stream of gas, providing the stream with the cooled, moisture-free exhaust gas, and also with a desired quantity of liquid, the tornado-like stream acting to shear the liquid and vaporize it, sending the stream with its exhaust gas and liquid vapor into the manifold with a low-pressure vortex center, thereby creating a vapor-laden whirling charge to each cylidner when its intake valve is open.

Lindberg, J.E.

1987-09-29

443

Chemical Looping Combustion Kinetics  

SciTech Connect

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

Edward Eyring; Gabor Konya

2009-03-31

444

Urea derivatives on the move: cytokinin-like activity and adventitious rooting enhancement depend on chemical structure.  

PubMed

Urea derivatives are synthetic compounds, some of which have proved to be positive regulators of cell division and differentiation. N-phenyl-N'-(2-chloro-4-pyridyl)urea (forchlorofenuron, CPPU) and N-phenyl-N'-(1,2,3-thiadiazol-5-yl)urea (thidiazuron, TDZ), well known urea cytokinin representatives, are extensively used in in vitro plant morphogenesis studies, as they show cytokinin-like activity often exceeding that of adenine compounds. In recent years, renewed interest in structure-activity relationship studies allowed identification of new urea cytokinins and other urea derivatives that specifically enhance adventitious root formation. In this review, we report the research history of urea derivatives, new insights into their biological activity, and recent progress on their mode of action. PMID:19470099

Ricci, A; Bertoletti, C

2009-05-01

445

One Step Combustion Synthesis Of YAG:Ce Phosphor For Solid State Lighting  

NASA Astrophysics Data System (ADS)

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

Yadav, Pooja; Gupta, K. Vijay Kumar; Muley, Aarti; Joshi, C. P.; Moharil, S. V.

2011-10-01

446

Band-gap modulation via gallium substitution in cerium doped gadolinium aluminum garnet using a mixed fuel combustion approach  

SciTech Connect

Cerium doped Gadolinium garnets (Gd{sub 3}Al{sub x}Ga{sub 5?x}O{sub 12} where 0?x?5) are synthesized via combustion synthesis using mixture of urea and glycine fuels. A 4h Post annealing at 1400 oC is found to be necessary for pure phase formation. Lattice spacing variation as a result of partial or total Ga substitution at Al site was mapped by X-ray diffraction. Photoluminescence emission of Ce shifts as a consequence of Ga substitution and therefore suggests a local re-adjustment of crystal field around activator site.

Tyagi, Mohit; Pitale, Shreyas S.; Ghosh, Manoranjan; Shinde, Seema [Crystal Technology Section, Technical Physics Division, Bhabha Atomic Research Centre, Mumbai- 400085 (India)

2014-04-24

447

Phosphate-triggered self-assembly of N-[(Uracil-5-yl)methyl]urea: a minimalistic urea-derived hydrogelator.  

PubMed

N-[(Uracil-5-yl)methyl]urea is reported as a minimalistic low-molecular-weight hydrogelator (LMWHG). The unusual phosphate-induced assembly of this compound has been thoroughly investigated by IR, UV/Vis, and NMR spectroscopy, electron microscopy, and rheological experiments. This rare example of an anion-triggered urea-based LMWHG is the first example of a pyrimidine- and urea-containing molecule that can be forced into self-assembly in aqueous solution without additional aromatic or lipophilic groups. The gelator/phosphate ratio within the hydrogel was successfully determined by (31) P?MAS?NMR spectroscopy. The hydrogel exhibits a very fast and repeatable self-healing property, and remarkable G' values. The viscoelastic properties of the hydrogel can easily be tuned by variation of the phosphate ratio. PMID:25042699

Kleinsmann, Alexander J; Weckenmann, Nicole M; Nachtsheim, Boris J

2014-07-28

448

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

449

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.

450

Jet plume injection and combustion system for internal combustion engines  

SciTech Connect

This invention is comprised of an improved combustion system for an internal combustion engine is disclosed wherein a rich air/fuel mixture is furnished at high pressure to one or more jet plume generator cavities adjacent to a cylinder and then injected through one or more orifices from the cavities into the head space of the cylinder to form one or more turbulent jet plumes in the head space of the cylinder prior to ignition of the rich air/fuel mixture in the cavity of the jet plume generator. The portion of the rich air/fuel mixture remaining in the cavity of the generator is then ignited to provide a secondary jet, comprising incomplete combustion products which are injected into the cylinder to initiate combustion in the already formed turbulent jet plume. Formation of the turbulent jet plume in the head space of the cylinder prior to ignition has been found to yield a higher maximum combustion pressure in the cylinder, as well as shortening the time period to attain such a maximum pressure.

Oppenheim, A.K.; Maxson, J.A.; Hensinger, D.M.

1992-12-31

451

Jet plume injection and combustion system for internal combustion engines  

DOEpatents

An improved combustion system for an internal combustion engine is disclosed wherein a rich air/fuel mixture is furnished at high pressure to one or more jet plume generator cavities adjacent to a cylinder and then injected through one or more orifices from the cavities into the head space of the cylinder to form one or more turbulent jet plumes in the head space of the cylinder prior to ignition of the rich air/fuel mixture in the cavity of the jet plume generator. The portion of the rich air/fuel mixture remaining in the cavity of the generator is then ignited to provide a secondary jet, comprising incomplete combustion products which are injected into the cylinder to initiate combustion in the already formed turbulent jet plume. Formation of the turbulent jet plume in the head space of the cylinder prior to ignition has been found to yield a higher maximum combustion pressure in the cylinder, as well as shortening the time period to attain such a maximum pressure. 24 figures.

Oppenheim, A.K.; Maxson, J.A.; Hensinger, D.M.

1993-12-21

452

Jet plume injection and combustion system for internal combustion engines  

DOEpatents

An improved combustion system for an internal combustion engine is disclosed wherein a rich air/fuel mixture is furnished at high pressure to one or more jet plume generator cavities adjacent to a cylinder and then injected through one or more orifices from the cavities into the head space of the cylinder to form one or more turbulent jet plumes in the head space of the cylinder prior to ignition of the rich air/fuel mixture in the cavity of the jet plume generator. The portion of the rich air/fuel mixture remaining in the cavity of the generator is then ignited to provide a secondary jet, comprising incomplete combustion products which are injected into the cylinder to initiate combustion in the already formed turbulent jet plume. Formation of the turbulent jet plume in the head space of the cylinder prior to ignition has been found to yield a higher maximum combustion pressure in the cylinder, as well as shortening the time period to attain such a maximum pressure.

Oppenheim, Antoni K. (Kensington, CA); Maxson, James A. (Berkeley, CA); Hensinger, David M. (Albany, CA)

1993-01-01

453

Transmembrane Exchange of Hyperpolarized 13C-Urea in Human Erythrocytes: Subminute Timescale Kinetic Analysis  

PubMed Central

The rate of exchange of urea across the membranes of human erythrocytes (red blood cells) was quantified on the 1-s to 2-min timescale. 13C-urea was hyperpolarized and subjected to rapid dissolution and the previously reported (partial) resolution of 13C NMR resonances from the molecules inside and outside red blood cells in suspensions was observed. This enabled a stopped-flow type of experiment to measure the (initially) zero-trans transport of urea with sequential single-pulse 13C NMR spectra, every second for up to ?2 min. Data were analyzed using Bayesian reasoning and a Markov chain Monte Carlo method with a set of simultaneous nonlinear differential equations that described nuclear magnetic relaxation combined with transmembrane exchange. Our results contribute to quantitative understanding of urea-exchange kinetics in the whole body; and the methodological approach is likely to be applicable to other cellular systems and tissues in vivo. PMID:24209840

Pagès, Guilhem; Puckeridge, Max; Liangfeng, Guo; Tan, Yee Ling; Jacob, Chacko; Garland, Marc; Kuchel, Philip W.

2013-01-01

454

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

E-print Network

fertilization, soils were periodically analyzed for microbial activity (arginine ammonification, AA; substrate induced respiration, SIR), ability to hydrolyze urea (UH), numbers of nitrifying bacteria, and nitrification potentials (Nps). Only soils from...

Waggoner, Paul James

1993-01-01

455

Synthesis and characterization of shape memory poly (epsilon-caprolactone) polyurethane-ureas.  

E-print Network

??A series of segmented poly (epsilon-caprolactone) polyurethane-ureas (PCLUUs) were prepared from poly (epsilon-caprolactone) (PCL) diol, different dissociates and chain extenders to improve the recovery stress… (more)

Ren, Hongfeng

2012-01-01

456

Estimation of antemortem serum electrolytes and urea concentrations from vitreous humor collected postmortem.  

PubMed Central

Electrolyte and urea levels of vitreous humor collected from bovine eyes at various times postmortem, were compared with serum levels in the same animals. Provided the vitreous humor was filtered immediately after collection, measured levels of total calcium (Ca), potassium ions (K+), sodium ions (Na+) and urea nitrogen were very consistent. For 24 hours postmortem the concentrations of Ca, Na+ and urea nitrogen remained stable, while K+ increased to approximately 55% more than the immediate postmortem level. A small study using anesthetized dogs indicated that urea nitrogen levels of vitreous humor take several hours to equilibrate with elevated blood levels. Analysis of vitreous humor may be a useful adjunct to diagnosis in cases where antemortem clinical chemistry is absent or inadequate. PMID:7093811

Wilkie, I W; Bellamy, J E

1982-01-01

457

[Effect of the urea fertilization in pasture on Rhipicephalus (Boophilus) microplus (Acari: Ixodidae)].  

PubMed

The objective of this study was to verify the effect of the urea fertilization in pasture on Rhipicephalus (Boophilus) microplus population in free living stage. Two groups had been made, a control group and a urea treatment group, each group with 10 lots of Mombaça grass (Panicum maximum cv. Mombaça). In day zero had been placed 12 engorged tick females in each lot and made fertilization with urea in the dosage of 60 g in the lots of the treat group. In 27th day the grass was cutted out in 1 to 5 lots of both groups and fertilized with urea in the lots of 1 to 5 in the treat group. In 40th day was released a white flannel 1.60 x 1.00 m length on each lot to verify the presence of larvae. The results presented a difference of 85.97% (P < 0.0001) between the treat group and the control group. PMID:20059818

Da Cunha, Arildo P; Bello, Ana Cristina P De Paiva; Leite, Romário C; Oliveira, Paulo R; Martins, João Ricardo; Ribeiro, Antônio Cândido C Leite; Domingues, Luisa N; De Freitas, Carolina Maria V; Bastianetto, Eduardo; Wanderley, Rebeca Passos Bispos; Dalla Rosa, Ricardo C

2008-09-01

458

Nickel-cobalt bimetallic anode catalysts for direct urea fuel cell  

PubMed Central

Nickel is an ideal non-noble metal anode catalyst for direct urea fuel cell (DUFC) due to its high activity. However, there exists a large overpotential toward urea electrooxidation. Herein, NiCo/C bimetallic nanoparticles were prepared with various Co contents (0, 10, 20, 30 and 40?wt%) to improve the activity. The best Co ratio was 10% in the aspect of cell performance, with a maximum power density of 1.57?mW cm?2 when 0.33?M urea was used as fuel, O2 as oxidant at 60°C. The effects of temperature and urea concentration on DUFC performance were investigated. Besides, direct urine fuel cell reaches a maximum power density of 0.19?mW cm?2 with an open circuit voltage of 0.38?V at 60°C. PMID:25168632

Xu, Wei; Zhang, Huimin; Li, Gang; Wu, Zucheng

2014-01-01

459

Urea, sugar, nonesterified fatty acid and cholesterol content of the blood in prolonged weightlessness  

NASA Technical Reports Server (NTRS)

Biochemical blood composition studies on astronauts during weightlessness flight simulation tests and during actual space flights showed some disturbances of metabolic processes. Increases in blood sugar, fatty acid and cholesterol, and urea content are noted.

Balakhovskiy, I. S.; Orlova, T. A.

1975-01-01

460

Theoretical studies of urea adsorption on single wall boron-nitride nanotubes  

NASA Astrophysics Data System (ADS)

Surface modification of a boron nitride nanotube (BNNT) with urea molecule was investigated in terms of its energetic, geometric, and electronic properties using B3LYP and PW91 density functionals. In this investigation, various armchair (n,n) nanotubes, where n = 5, 6, 7 have been used. Two different interaction modes, including interaction with outer layer and inner layer of tube were studied. The results indicated that the adsorption of single urea molecule in all of its configurations is observed to be exothermic and physical in nature. Interestingly, the adsorption energy for the most stable configuration of urea was observed when the molecule located inside of the nanotube. Besides, the adsorption of urea on BNNTs changes the conductivity of nanotube.

Chermahini, Alireza Najafi; Teimouri, Abbas; Farrokhpour, Hossein

2014-11-01

461

Combustion Iron Distribution and Deposition  

NASA Astrophysics Data System (ADS)

Iron is hypothesized to be an important micronutrient for ocean biota, thus modulating carbon dioxide uptake by the ocean biological pump. Studies have assumed that atmospheric deposition of iron to the open ocean is predominantly from mineral aerosols. For the first time, we model the source, transport and deposition of iron from combustion sources. Iron is produced in small quantities during fossil fuel burning, incinerator use, and biomass burning. The sources of combustion iron are concentrated in the industrialized regions and biomass burning regions, largely in the tropics. Model results suggest that combustion iron can represent up to 50 percent of the total iron deposited, but over open ocean regions is usually less than 5 percent of the total iron, with the highest values (less than 30 percent) close to the East Asian continent in the North Pacific. For ocean biogeochemistry the bioavailability of the iron is important, and this is often estimated by the fraction which is soluble (Fe(II)). Previous studies have argued that atmospheric processing of the relatively insoluble Fe(III) occurs to make it more soluble (Fe(II)). Modeled estimates of soluble iron amounts based solely on atmospheric processing as simulated here cannot match the variability in daily averaged in situ concentration measurements in Korea, which is located close to both combustion and dust sources. The best match to the observations is that there is substantial direct emissions of soluble iron from combustion processes. If we assume observed soluble Fe/black carbon (BC) ratios in Korea are representative of the whole globe, we obtain the result that deposition of soluble iron from combustion contribute 20-100 percent of the soluble iron deposition over many ocean regions. This implies that more work should be done refining the emissions and deposition of combustion sources of soluble iron globally.

Luo, C.; Mahowald, N.; Bond, T.; Chuang, P.; Artaxo, P.; Siefert, R.; Chen, Y.; Schauer, J.

2007-05-01

462

Combustion iron distribution and deposition  

NASA Astrophysics Data System (ADS)

Iron is hypothesized to be an important micronutrient for ocean biota, thus modulating carbon dioxide uptake by the ocean biological pump. Studies have assumed that atmospheric deposition of iron to the open ocean is predominantly from mineral aerosols. For the first time we model the source, transport, and deposition of iron from combustion sources. Iron is produced in small quantities during fossil fuel burning, incinerator use, and biomass burning. The sources of combustion iron are concentrated in the industrialized regions and biomass burning regions, largely in the tropics. Model results suggest that combustion iron can represent up to 50% of the total iron deposited, but over open ocean regions it is usually less than 5% of the total iron, with the highest values (<30%) close to the East Asian continent in the North Pacific. For ocean biogeochemistry the bioavailability of the iron is important, and this is often estimated by the fraction which is soluble (Fe(II)). Previous studies have argued that atmospheric processing of the relatively insoluble Fe(III) occurs to make it more soluble (Fe(II)). Modeled estimates of soluble iron amounts based solely on atmospheric processing as simulated here cannot match the variability in daily averaged in situ concentration measurements in Korea, which is located close to both combustion and dust sources. The best match to the observations is that there are substantial direct emissions of soluble iron from combustion processes. If we assume observed soluble Fe/black carbon ratios in Korea are representative of the whole globe, we obtain the result that deposition of soluble iron from combustion contributes 20-100% of the soluble iron deposition over many ocean regions. This implies that more work should be done refining the emissions and deposition of combustion sources of soluble iron globally.

Luo, Chao; Mahowald, N.; Bond, T.; Chuang, P. Y.; Artaxo, P.; Siefert, R.; Chen, Y.; Schauer, J.

2008-03-01

463

The urea decomposition product cyanate promotes endothelial dysfunction.  

PubMed

The dramatic cardiovascular mortality of patients with chronic kidney disease is attributable in a significant proportion to endothelial dysfunction. Cyanate, a reactive species in equilibrium with urea, is formed in excess in chronic kidney disease. Cyanate is thought to have a causal role in promoting cardiovascular disease, but the underlying mechanisms remain unclear. Immunohistochemical analysis performed in the present study revealed that carbamylated epitopes associate mainly with endothelial cells in human atherosclerotic lesions. Cyanate treatment of human coronary artery endothelial cells reduced expression of endothelial nitric oxide synthase, and increased tissue factor and plasminogen activator inhibitor-1 expression. In mice, administration of cyanate, promoting protein carbamylation at levels observed in uremic patients, attenuated arterial vasorelaxation of aortic rings in response to acetylcholine without affecting the sodium nitroprusside-induced relaxation. Total endothelial nitric oxide synthase and nitric oxide production were significantly reduced in aortic tissue of cyanate-treated mice. This coincided with a marked increase of tissue factor and plasminogen activator inhibitor-1 protein levels in aortas of cyanate-treated mice. Thus, cyanate compromises endothelial functionality in vitro and in vivo. This may contribute to the dramatic cardiovascular risk of patients suffering from chronic kidney disease. PMID:24940796

El-Gamal, Dalia; Rao, Shailaja P; Holzer, Michael; Hallström, Seth; Haybaeck, Johannes; Gauster, Martin; Wadsack, Christian; Kozina, Andrijana; Frank, Saša; Schicho, Rudolf; Schuligoi, Rufina; Heinemann, Akos; Marsche, Gunther

2014-11-01

464

Dynamic flow control strategies of vehicle SCR Urea Dosing System  

NASA Astrophysics Data System (ADS)

Selective Catalyst Reduction(SCR) Urea Dosing System(UDS) directly affects the system accuracy and the dynamic response performance of a vehicle. However, the UDS dynamic response is hard to keep up with the changes of the engine's operating conditions. That will lead to low NO X conversion efficiency or NH3 slip. In order to optimize the injection accuracy and the response speed of the UDS in dynamic conditions, an advanced control strategy based on an air-assisted volumetric UDS is presented. It covers the methods of flow compensation and switching working conditions. The strategy is authenticated on an UDS and tested in different dynamic conditions. The result shows that the control strategy discussed results in higher dynamic accuracy and faster dynamic response speed of UDS. The inject deviation range is improved from being between -8% and 10% to -4% and 2% and became more stable than before, and the dynamic response time was shortened from 200 ms to 150 ms. The ETC cycle result shows that after using the new strategy the NH3 emission is reduced by 60%, and the NO X emission remains almost unchanged. The trade-off between NO X conversion efficiency and NH3 slip is mitigated. The studied flow compensation and switching working conditions can improve the dynamic performance of the UDS significantly and make the UDS dynamic response keep up with the changes of the engine's operating conditions quickly.

Lin, Wei; Zhang, Youtong; Asif, Malik

2015-01-01

465

A novel disposable electrochemical immunosensor for phenyl urea herbicide diuron.  

PubMed

A disposable electrochemical immunosensor has been developed for the determination of phenyl urea herbicide-diuron using a low cost laser ablated gold electrodes (LC-LAGE) fabricated on polystyrene substrate. The electrodes were electrochemically deposited with prussian blue-gold nanoparticle (PB-GNP) film, and a competitive inhibition immunoassay was performed on LC-LAGE by using a specific hapten-protein conjugate. The binding of available diuron specific antibody on conjugate coated electrode was detected using alkaline phosphatase rabbit anti-IgG antibody. The addition of 1-naphthyl phosphate substrate resulted in the production of electrochemically active product, 1-naphthol, which was monitored using square wave voltammetry technique. The assay exhibited an excellent sensitivity and specificity showing the dynamic response range between 1 ppt and 10 ppm for diuron with detection limit around 1 ppt. This study provides insight into development of a rapid and high-throughput screening of pesticides in environmental samples at a very low cost. PMID:21530227

Sharma, Priyanka; Sablok, Kavita; Bhalla, Vijayender; Suri, C Raman

2011-06-15

466

Preparation and properties of adjacency crosslinked polyurethane-urea elastomers  

NASA Astrophysics Data System (ADS)

Adjacency crosslinked polyurethane-urea (PUU) elastomers with different crosslinking density were prepared by using hydroxyl-terminated liquid butadiene-nitrile (HTBN), toluene diisocyanate (TDI) and chain extender 3,5-dimethyl thio-toluene diamine (DMTDA) as raw materials, dicumyl peroxide (DCP) as initiator, and N,N'-m-phenylene dimaleimide (HVA-2) as the crosslinking agent. The influences of the crosslinking density and temperature on the structure and properties of such elastomers were investigated. The crosslinking density of PUU elastomer was tested by the NMR method. It is found that when the content of HVA-2 is 1.5%, the mechanical properties of polyurethane elastomer achieve optimal performance. By testing thermal performance of PUU, compared with linear PUU, the thermal stability of the elastomers has a marked improvement. With the addition of HVA-2, the loss factor tan ? decreases. FT-IR spectral studies of PUU elastomer at various temperatures were performed. From this study, heat-resistance polyurethane could be prepared, and the properties of PUU at high temperature could be improved obviously.

Wu, Yuan; Cao, Yu-Yang; Wu, Shou-Peng; Li, Zai-Feng

2012-12-01

467

A novel mathematical method based on urea kinetic modeling for computing the dialysis dose.  

PubMed

A novel normalized single pool urea kinetic model (nspUKM) for the quantification of the urea removal, dialyzer urea clearance and urea generation rate during a dialysis session, is presented. Its major goal is the computation of an accurate estimate of the fractional dialyzer urea clearance (dKt/V), which is denoted nKt/V, in contrast to the equilibrated Kt/V (eKt/V). This work clarifies the significance of dKt/V as a complement to eKt/V in hemodialysis (HD) prescription and quantification. This new model emerges from a generalization of the standard single pool urea kinetic model (spUKM) of the US National Cooperative Dialysis Study (NCDS), identified as gspUKM. Due to their significance, the standard single pool Kt/V (spKt/V) and the eKt/V are also analyzed from gspUKM in this work, with the aim of achieving a better interpretation of the results. Indices nKt/V, eKt/V and spKt/V have been compared with the dKt/V computed from a published and validated two-pool urea kinetic model (2pUKM). We present the results obtained from a clinical study carried out on a group of 30 end stage renal disease (ESRD) patients. The limits of agreement (mean+/-2S.D. (standard deviation) of the difference) between nKt/V and 2pKt/V were -0.077+/-0.72% (percentage of the dKt/V mean), while between eKt/V and 2pKt/V were -13.75+/-17.39% and between spKt/V and 2pKt/V were -1.61+/-6.54%. These scores prove that the nspUKM model is able to provide a very accurate estimate of 2pKt/V and thus dKt/V, even with high flux (HF) HD. The presented method joins the simplicity of single-pool models to the accuracy of double-pool models, when the target is the identification of the dialyzer urea clearance, urea removal and urea generation rate, although it does not provide a good prediction of the urea dynamics. Finally, we think that our analytical and experimental findings throw light on the behavior and applicability of the different Kt/V indices analyzed. PMID:15013593

Prado, Manuel; Roa, Laura; Palma, Alfonso; Milán, José Antonio

2004-05-01

468

Computing and combustion  

NASA Technical Reports Server (NTRS)

Coming into the Combustion Branch of the Turbomachinery and Propulsion Systems Division, there was not any set project planned out for me to work on. This was understandable, considering I am only at my sophmore year in college. Also, my mentor was a division chief and it was expected that I would be passed down the line. It took about a week for me to be placed with somebody who could use me. My first project was to write a macro for TecPlot. Commonly, a person would have a 3D contour volume modeling something such as a combustion engine. This 3D volume needed to have slices extracted from it and made into 2D scientific plots with all of the appropriate axis and titles. This was very tedious to do by hand. My macro needed to automate the process. There was some education I needed before I could start, however. First, TecPlot ran on Unix and Linux, like a growing majority of scientific applications. I knew a little about Linux, but I would need to know more to use the software at hand. I took two classes at the Learning Center on Unix and am now comfortable with Linux and Unix. I already had taken Computer Science I and II, and had undergone the transformation from Computer Programmer to Procedural Epistemologist. I knew how to design efficient algorithms, I just needed to learn the macro language. After a little less than a week, I had learned the basics of the language. Like most languages, the best way to learn more of it was by using it. It was decided that it was best that I do the macro in layers, starting simple and adding features as I went. The macro started out slicing with respect to only one axis, and did not make 2D plots out of the slices. Instead, it lined them up inside the solid. Next, I allowed for more than one axis and placed each slice in a separate frame. After this, I added code that transformed each individual slice-frame into a scientific plot. I also made frames for composite volumes, which showed all of the slices in the same XYZ space. I then designed an addition companion macro that exported each frame into its own image file. I then distributed the macros to a test group, and am awaiting feedback. In the meantime, a am researching the possible applications of distributed computing on the National Combustor Code. Many of our Linux boxes were idle for most of the day. The department thinks that it would be wonderful if we could get all of these idle processors to work on a problem under the NCC code. The client software would have to be easily distributed, such as in screensaver format or as a program that only ran when the computer was not in use. This project proves to be an interesting challenge.

Thompson, Daniel

2004-01-01

469

Measurement and modelling of urea solubility in supercritical CO 2 and CO 2 + ethanol mixtures  

Microsoft Academic Search

The solubility of urea in supercritical CO2 and CO2+ethanol was measured over the pressure and temperature ranges 100–300bar and 313–373K, respectively, and ethanol concentrations of 0–25mass% (urea free basis). The solubility in CO2 was measured by a once-through packed bed gravimetric method at a laboratory and pilot scale. The solubility in CO2+ethanol was measured using two different methods: antisolvent precipitation

O. J. Catchpole; S. J. Tallon; P. J. Dyer; J.-S. Lan; B. Jensen; O. K. Rasmussen; J. B. Grey

2005-01-01

470

Milk urea as nutritional indicator in sheep grazing legume-based pastures  

Microsoft Academic Search

A three-year study was carried out to assess the effects of different grass-legume mixtures on: (i) dietary CP and NEL (Net Energy for milk production) concentrations and milk urea level; and (ii) the relationship between milk urea and several dietary variables. Replicate groups of Sardinian sheep in early-mid lactation (January-May) rotationally grazed plots of three grass-legume mixtures consisting of common

G. Molle; V. Giovanetti; A. Cabiddu; M. Cuccureddu; G. Scanu; M. Decandia

471

Thermal unfolding of dodecameric glutamine synthetase: inhibition of aggregation by urea.  

PubMed Central

Thermal unfolding of dodecameric manganese glutamine synthetase (622,000 M(r)) at pH 7 and approximately 0.02 ionic strength occurs in two observable steps: a small reversible transition (Tm approximately 42 degrees C; delta H approximately equal to 0.9 J/g) followed by a large irreversible transition (Tm approximately 81 degrees C; delta H approximately equal to 23.4 J/g) in which secondary structure is lost and soluble aggregates form. Secondary structure, hydrophobicity, and oligomeric structure of the equilibrium intermediate are the same as for the native protein, whereas some aromatic residues are more exposed. Urea (3 M) destabilizes the dodecamer (with a tertiary structure similar to that without urea at 55 degrees C) and inhibits aggregation accompanying unfolding at < or = 0.2 mg protein/mL. With increasing temperature (30-70 degrees C) or incubation times at 25 degrees C (5-35 h) in 3 M urea, only dodecamer and unfolded monomer are detected. In addition, the loss in enzyme secondary structure is pseudo-first-order (t1/2 = 1,030 s at 20.0 degrees C in 4.5 M urea). Differential scanning calorimetry of the enzyme in 3 M urea shows one endotherm (Tmax approximately 64 degrees C; delta H = 17 +/- 2 J/g). The enthalpy change for dissociation and unfolding agrees with that determined by urea titrations by isothermal calorimetry (delta H = 57 +/- 15 J/g; Zolkiewski M, Nosworthy NJ, Ginsburg A, 1995, Protein Sci 4: 1544-1552), after correcting for the binding of urea to protein sites exposed during unfolding (-42 J/g). Refolding and assembly to active enzyme occurs upon dilution of urea after thermal unfolding. PMID:9416610

Nosworthy, N. J.; Ginsburg, A.

1997-01-01

472

Soil emissions of nitric oxide and nitrous oxide from injected anhydrous ammonium and urea  

SciTech Connect

This study characterizes soil emissions of NO and N{sub 2}O from banded applications of anhydrous ammonium (AA) and urea over the period from 6 May 1994 to 12 September 1994 from a losses soil in western Tennessee. The N application rate for both sources was 168 kg ha{sup {minus}1}. Fertilizer type strongly influenced emissions of N{sub 2}O (F = 231; P = 0.0001) and NO (F = 69; P = 0.0001). During the 129 d measurement period, the AA treatment lost 12.33 Kg of N{sub 2}O-N or 7.33% of the applied N. The N{sub 2}O-N loss from the urea treatment was about one-half that from AA; 6.34 kg ha{sup {minus}1} or 3.77% of the applied N. Loss of NO-N from both treatment was small compared with N{sub 2}O-N loss. The urea treatment lost 0.27 kg ha{sup {minus}1} as NO-N and the AA treatment lost 0.2 kg ha{sup {minus}1} during the study period. While the measured loss rate of N{sub 2}O-N from AA is similar to previous literature estimates, our values for urea are 20 to 40 times greater than the current literature reports of N{sub 2}O-N loss of 0.1 to 0.2% of the urea applied. Higher N{sub 2}O losses from urea in this study may be related to the fact that urea was banded below the soil surface, whereas urea has been broadcast on the soil surface in other N{sub 2}O emissions studies. 31 refs., 5 figs., 2 tabs.

Thornton, F.C.; Bock, B.R.; Tyler, D.D. [TVA, Environment Research Center, Muscle Shoals, AL (United States)]|[Univ. of Tennessee, Jackson, TN (United States)

1996-11-01

473

Removal of urea in a wearable dialysis device: a reappraisal of electro-oxidation.  

PubMed

A major challenge for a wearable dialysis device is removal of urea, as urea is difficult to adsorb while daily production is very high. Electro-oxidation (EO) seems attractive because electrodes are durable, small, and inexpensive. We studied the efficacy of urea oxidation, generation of chlorine by-products, and their removal by activated carbon (AC). EO units were designed. Three electrode materials (platinum, ruthenium oxide, and graphite) were compared in single pass experiments using urea in saline solution. Chlorine removal by AC in series with EO by graphite electrodes was tested. Finally, urea-spiked bovine blood was dialyzed and dialysate was recirculated in a dialysate circuit with AC in series with an EO unit containing graphite electrodes. Platinum electrodes degraded more urea (21 ± 2 mmol/h) than ruthenium oxide (13 ± 2 mmol/h) or graphite electrodes (13 ± 1 mmol/h). Chlorine generation was much lower with graphite (13 ± 4 mg/h) than with platinum (231 ± 22 mg/h) or ruthenium oxide electrodes (129 ± 12 mg/h). Platinum and ruthenium oxide electrodes released platinum (4.1 [3.9-8.1] umol/h) and ruthenium (83 [77-107] nmol/h), respectively. AC potently reduced dialysate chlorine levels to < 0.10 mg/L. Urea was removed from blood by EO at constant rate (9.5 ± 1.0 mmol/h). EO by graphite electrodes combined with AC shows promising urea removal and chlorine release complying with Association for the Advancement of Medical Instrumentation standards, and may be worth further exploring for dialysate regeneration in a wearable system. PMID:24750025

Wester, Maarten; Simonis, Frank; Lachkar, Nadia; Wodzig, Will K; Meuwissen, Frank J; Kooman, Jeroen P; Boer, Walther H; Joles, Jaap A; Gerritsen, Karin G

2014-12-01

474

Structural, spectral, thermal, dielectric, mechanical and optical properties of urea l-alanine acetate single crystals  

Microsoft Academic Search

A new organic nonlinear optical crystal, urea l-alanine acetate (ULAA) has been grown by solution growth using slow cooling technique with the vision to improve the properties of the l-alanine crystals. Urea and l-alanine material were mixed in the molar ratio 1:4. Solubility and metastable zone width were determined. Single crystal XRD analyses revealed that the crystal lattice of ULAA

D. Jaikumar; S. Kalainathan; G. Bhagavannarayana

2010-01-01

475

Study of Properties of Urea and L-?-Alanine Didoped Triglycine Sulfate (UrLATGS) Crystals  

Microsoft Academic Search

In this report, the properties of triglycine sulfate (TGS) crystals doped with urea and L-a-alanine were studied. Urea and L-a-alanine have successfully entered into TGS crystal, demonstrated by infrared transmission spectrum and pyroelectric study. Figures of merit and Curie temperature are increased due to these two additions. UrLATGS is more suitable for infrared detectors than pure TGS crystals.

Genshui Wang; Xiangjian Meng; Weiming Zheng; Xiaoguang Wang; Jian Yu; Junhao Chu

2001-01-01

476

EFFECTS OF INCREMENTAL UREA SUPPLEMENTATION ON RUMINAL AMMONIA CONCENTRATION AND BACTERIAL PROTEIN FORMATION 1 ,2  

Microsoft Academic Search

Summary Increments of O, I, 2, 3, 4.5 and 6.5% crude protein equivalent (CPE) were added as urea to a basal diet containing 75% corn and 20% cottonseed hulls (8.3% protein from all natural sources) and fed to two nonlactating Holstein cows. Ruminal ammonia nitrogen (N) levels increased (P<.05) with each increment of urea and ranged from 1.3 (basal) to

J. H. Kang-Meznarich; G. A. Broderick; Texas A

477

Portable urea biosensor based on the extended-gate field effect transistor  

Microsoft Academic Search

In this study, extended-gate field effect transistor (EGFET) was applied to fabricate disposable urea biosensor. And the 1.5V low-voltage instrument amplifier was adopted to realize the portable urea biosensor. However, the difference between extended-gate field effect transistor and traditional ion-selective field effect transistor is the position of the sensitive membrane. The extended-gate field effect transistor was separated into two parts,

Jia-Chyi Chen; Jung-Chuan Chou; Tai-Ping Sun; Shen-Kan Hsiung

2003-01-01

478

Portable urea biosensor based on the extended base bipolar junction transistor  

Microsoft Academic Search

In this study, an extended base bipolar junction transistor (EBBJT) was proposed to fabricate disposable urea biosensor. The detection of the urea is based on the variation of pH value. The gels, fabricated by the poly vinyl alcohol with pendent styrylpyridinium groups, were used to immobilize the urease. The SnO2\\/ITO glass, fabricated by sputtering SnO2 on the conductive ITO glass,

Chung-Yuan Chen; Hsiu-Li Shieh; Tai-Ping Sun

2010-01-01

479

Urea-SCR: a promising technique to reduce NO x emissions from automotive diesel engines  

Microsoft Academic Search

Urea-SCR, the selective catalytic reduction using urea as reducing agent, has been investigated for about 10 years in detail and today is a well established technique for DeNOx of stationary diesel engines. It is presently also considered as the most promising way to diminish NOx emissions originating from heavy duty vehicles, especially trucks.The paper discusses the fundamental problems and challenges

M. Koebel; M. Elsener; M. Kleemann

2000-01-01

480

Synthesis and characterization of some single crystals of thiourea urea zinc chloride  

Microsoft Academic Search

Thiourea Urea Zinc (II) Chloride (TUZC), a new semiorganic non-linear optical material has been synthesized. The solubility\\u000a studies have been carried out at room temperature. Single crystals of different proportions of TUZC have been grown by slow\\u000a evaporation of saturated aqueous solution at room temperature. The FTIR and UV spectral bands have been compared with urea,\\u000a thiourea and bis Thiourea

B. Ravindran; G. Madhurambal; M. Mariappan; S. C. Mojumdar

2011-01-01

481

4-Quinazolinyloxy-diaryl ureas as novel BRAFV600E inhibitors.  

PubMed

Aryl phenyl ureas with a 4-quinazolinoxy substituent at the meta-position of the phenyl ring are potent inhibitors of mutant and wild type BRAF kinase. Compound 7 (1-(5-tert-butylisoxazol-3-yl)-3-(3-(6,7-dimethoxyquinazolin-4-yloxy)phenyl)urea hydrochloride) exhibits good pharmacokinetic properties in rat and mouse and is efficacious in a mouse tumor xenograft model following oral dosing. PMID:21807507

Holladay, Mark W; Campbell, Brian T; Rowbottom, Martin W; Chao, Qi; Sprankle, Kelly G; Lai, Andiliy G; Abraham, Sunny; Setti, Eduardo; Faraoni, Raffaella; Tran, Lan; Armstrong, Robert C; Gunawardane, Ruwanthi N; Gardner, Michael F; Cramer, Merryl D; Gitnick, Dana; Ator, Mark A; Dorsey, Bruce D; Ruggeri, Bruce R; Williams, Michael; Bhagwat, Shripad S; James, Joyce

2011-09-15

482

Urea-temperature phase diagrams capture the thermodynamics of denatured state expansion that accompany protein unfolding  

PubMed Central

We have analyzed the thermodynamic properties of the von Willebrand factor (VWF) A3 domain using urea-induced unfolding at variable temperature and thermal unfolding at variable urea concentrations to generate a phase diagram that quantitatively describes the equilibrium between native and denatured states. From this analysis, we were able to determine consistent thermodynamic parameters with various spectroscopic and calorimetric methods that define the urea–temperature parameter plane from cold denaturation to heat denaturation. Urea and thermal denaturation are experimentally reversible and independent of the thermal scan rate indicating that all transitions are at equilibrium and the van't Hoff and calorimetric enthalpies obtained from analysis of individual thermal transitions are equivalent demonstrating two-state character. Global analysis of the urea–temperature phase diagram results in a significantly higher enthalpy of unfolding than obtained from analysis of individual thermal transitions and significant cross correlations describing the urea dependence of and that define a complex temperature dependence of the m-value. Circular dichroism (CD) spectroscopy illustrates a large increase in secondary structure content of the urea-denatured state as temperature increases and a loss of secondary structure in the thermally denatured state upon addition of urea. These structural changes in the denatured ensemble make up ?40% of the total ellipticity change indicating a highly compact thermally denatured state. The difference between the thermodynamic parameters obtained from phase diagram analysis and those obtained from analysis of individual thermal transitions illustrates that phase diagrams capture both contributions to unfolding and denatured state expansion and by comparison are able to decipher these contributions. PMID:23813497

Tischer, Alexander; Auton, Matthew