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1

Infrared and Raman Spectral Studies of Zirconium Hydrated Nitrate  

Microsoft Academic Search

FTIR and Raman spectra of hydratred zirconium nitrate (ZrO(NO3)2.xH2O powdered sample are recorded. The vibrational bands are assigned as fundamental vibrations of NO3- anion and that of water. The observed splitting of v1 (1047 and 1030 cm-1)mode in the Raman spectrum is due to the presence of two distinct types of nitrate groups with an average N-O distance of 1.257

Jobi Jose; M. Junaid Bushiri; K. Jayakumar; V. K. Vaidyan

2008-01-01

2

Infrared and Raman Spectral Studies of Zirconium Hydrated Nitrate  

Microsoft Academic Search

FTIR and Raman spectra of hydratred zirconium nitrate (ZrO(NO3)2?xH2O powdered sample are recorded. The vibrational bands are assigned as fundamental vibrations of NO3? anion and that of water. The observed splitting of v1 (1047 and 1030 cm?1)mode in the Raman spectrum is due to the presence of two distinct types of nitrate groups with an average N&sngbnd;O distance of 1.257

Jobi Jose; M. Junaid Bushiri; K. Jayakumar; V. K. Vaidyan

2008-01-01

3

Synthesis and characterization of pure cubic zirconium oxide nanocrystals by decomposition of bis-aqua, tris-acetylacetonato zirconium(IV) nitrate as new precursor complex  

Microsoft Academic Search

Pure zirconium oxide (ZrO2) nanocrystals with diameters 10–30nm are fabricated from bis-aqua, tris-acetylacetonato zirconium(IV) nitrate; [Zr(acac)3(H2O)2](NO3); by thermal decomposition. The different combinations of oleylamine, or polyethyleneglycol (PEG) and triphenylphosphine, were added as surfactants to control the particle size. The products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), ultraviolet–visible (UV–Vis) spectroscopy, photoluminescence spectroscopy (PL), Fourier transform infrared (FT-IR)

Masoud Salavati-Niasari; Mahnaz Dadkhah; Fatemeh Davar

2009-01-01

4

Zirconium  

USGS Publications Warehouse

Zirconium is the 20th most abundant element in the Earth’s crust. It occurs in a variety of rock types and geologic environments but most often in igneous rocks in the form of zircon (ZrSiO4). Zircon is recovered as a coproduct of the mining and processing of heavy mineral sands for the titanium minerals ilmenite and rutile. The sands are formed by the weathering and erosion of rock containing zircon and titanium heavy minerals and their subsequent concentration in sedimentary systems, particularly in coastal environments. A small quantity of zirconium, less than 10 kt/a (11,000 stpy), compared with total world production of 1.4 Mt (1.5 million st) in 2012, was derived from the mineral baddeleyite (ZrO2), produced from a single source in Kovdor, Russia.

Bedinger, G. M.

2013-01-01

5

Development of a continuous process for adjusting nitrate, zirconium, and free hydrofluoric acid concentrations in zirconium fuel dissolver product  

SciTech Connect

In the Fluorinel Dissolution Process (FDP) upgrade, excess hydrofluoric acid in the dissolver product must be complexed with aluminum nitrate (ANN) to eliminate corrosion concerns, adjusted with nitrate to facilitate extraction, and diluted with water to ensure solution stability. This is currently accomplished via batch processing in large vessels. However, to accommodate increases in projected throughput and reduce water production in a cost-effective manner, a semi-continuous system (In-line Complexing (ILC)) has been developed. The major conclusions drawn from tests demonstrating the feasibility of this concept are given in this report.

Cresap, D.A.; Halverson, D.S.

1993-04-01

6

ADSORPTION AND RECOVERY OF NITRATED POLYCYCLIC AROMATIC HYDROCARBONS ON HYBRID SURFACTANT EXPANDED ZIRCONIUM-PHOSPHATE  

Microsoft Academic Search

This paper focuses on the removal of nitro substituted polycyclic aromatic hydrocarbon compounds (NPAHs) from water using low cost synthesized zirconium phosphate mesoporous materials. These materials are lamellar type incorporating n-alkyl-(n = 12 and n = 16) trimethylamonium bromide molecules with different concentrations. For comparison of their performance as adsorbents and in the recovery of NPAH, their results were compared

M. Algarra; M. V. Jiménez; F. G. Sánchez; J. Soto; J. J. Jiménez; Joaquim C. G. Esteves da Silva

2009-01-01

7

COMPOSITION OF ZIRCONIUM AND HAFNIUM CUPFERRONATES  

Microsoft Academic Search

The composition of Zr and Hf cupferronates prepared at various acidtties ; and aging times was analyzed. Cup ferronate reactions with Zr\\/sup 4+\\/ or strong ; complexes of zirconium fluoride, sulfate, or nitrate precipitate into ; concentration on zirconium or hafnium cupferronate composition was studied. In ; weakly acid solutions both Hf and Zr form variable composition cupferronates. ; (R.V.L.);

K. F. Karlysheva; I. A. Sheka

1962-01-01

8

Structure characteristics of disordered zirconium hydroxoxides  

Microsoft Academic Search

The structural characteristics of low-temperature zirconium hydroxoxide and zirconium dioxide obtained from zirconyl nitrate\\u000a and treated at 383 and 653 K have been studied by the X-ray method of distribution of radial electron density. It is shown\\u000a that the low-temperature hydroxide contains a ?10 to 15-? nucleus of the crystalline phase with a structure of short-range\\u000a order similar to the

D. A. Zyuzin; E. M. Moroz; A. S. Ivanova; A. N. Shmakov

2003-01-01

9

Extraction of zirconium nitrate by TBP in n-octane: influence of cation type on third phase formation according to the "sticky spheres" model.  

PubMed

Small-angle neutron scattering (SANS) data for the tri-n-butyl phosphate (TBP)-n-octane, HNO(3)-Zr(NO(3))(4) solvent extraction system, obtained under a variety of experimental conditions, have been interpreted using the Baxter model for hard spheres with surface adhesion. The increase in scattering intensity in the low Q range observed when increasing amounts of Zr(NO(3))(4) were extracted into the organic phase was interpreted as arising from interactions between small reverse micelle-like particles containing two to three TBP molecules. Upon extraction of Zr(NO(3))(4), the particles interact through attractive forces between their polar cores with a potential energy that exceeds 2 k(B)T. The interparticle attraction, under suitable conditions, leads to third phase formation. A linear relationship exists between the derivative of the potential energy of attraction with respect to the concentration of nitrate ions in the organic phase and the ionization potential or the hydration enthalpy of the extracted metal cations. PMID:15568827

Chiarizia, Renato; Jensen, Mark P; Rickert, Paul G; Kolarik, Zdenek; Borkowski, Marian; Thiyagarajan, Pappanan

2004-12-01

10

EXTRACTION WITH TRIBUTYL PHOSPHATE (TBP) FROM FERRIC NITRATE SOLUTIONS  

Microsoft Academic Search

Ferric nitrate acts as a strong salting-out agent in the extraction of thorium(IV), uranyl, europium(III), samarium(III) and zirconium(IV) nitrates as well as of nitric acid with tributyl phosphate in dodecane. Nitric acid, if present in the extraction system together with large amounts of ferric nitrate, markedly suppresses the extraction of thorium(IV) and lanthanides(III) but significantly supports the extraction of zirconium(IV).

Z. Kolarik; K. Grudpan

1985-01-01

11

Manage corrosion with zirconium  

SciTech Connect

Zirconium has been used to construct process equipment for over three decades. Zirconium offers low maintenance costs, high reliability, and strong environmental protection with several other advantages: (1) it resists attack by strong acids and caustics, as well as by many salt solutions and molten salts; (2) zirconium has adequate strength for process equipment operating at elevated temperatures; (3) it is relatively low in density, high in thermal conductivity, and low in the coefficient of thermal expansion; (4) zirconium can be fabricated into almost any shape by conventional methods; (5) it is nontoxic and biocompatible; and (6) zirconium does not produce colored ions. The paper looks at some of the major applications of zirconium to better understand its use. The corrosives cited include acetic, formic, nitric, sulfuric, and lactic acids, and phenolic resins.

Yau, T.L.; Bird, K.W.

1995-01-01

12

Nitrate Protocol  

NSDL National Science Digital Library

The purpose of this resource is to measure the nitrate-nitrogen of water. Students will use a nitrate kit to measure the nitrate-nitrogen in the water at their hydrology site. The exact procedure depends on the instructions in the nitrate kit used.

The GLOBE Program, UCAR (University Corporation for Atmospheric Research)

2003-08-01

13

Nitrate reduction  

DOEpatents

Nitrates are reduced to nitrogen gas by contacting the nitrates with a metal to reduce the nitrates to nitrites which are then contacted with an amide to produce nitrogen and carbon dioxide or acid anions which can be released to the atmosphere. Minor amounts of metal catalysts can be useful in the reduction of the nitrates to nitrites. Metal salts which are formed can be treated electrochemically to recover the metals.

Dziewinski, Jacek J. (Los Alamos, NM); Marczak, Stanislaw (Los Alamos, NM)

2000-01-01

14

Influence of zirconium doping on the activities of zirconium and iodine co-doped titanium dioxide in the decolorization of methyl orange under visible light irradiation  

Microsoft Academic Search

Zirconium and iodine co-doped titanium dioxide (Zr–I–TiO2) was prepared by the hydrolysis of tetrabutyl titanate, premixed with zirconium nitrate in an iodic acid aqueous solution, followed by calcination in air. The structure and properties of the resultant catalyst powders were characterized by X-ray diffraction, the Brunauer–Emmett–Teller method, X-ray photoelectron spectroscopy, transmission electron microscopy, and UV–vis absorption spectroscopy. The catalytic activity

Shuang Song; Fangyue Hong; Zhiqiao He; Hongyu Wang; Xianghong Xu; Jianmeng Chen

2011-01-01

15

OXIDATION OF ZIRCONIUM AND ZIRCONIUM ALLOYS  

Microsoft Academic Search

Zirconium oxidation was investigaied in the temperature range 400 io 900 ; deg C at oxygen pressures of 50, 200, and 800 mm. The reaction rate of massive ; (parallelepiped) samples was best expressed by the cubic rate law. At an oxygen ; pressure of 200 mm the activation energy was calculated to be 42.7 kcal per mole, ; and

H. A. Porte; J. G. Schnizlein; R. C. Vogel; D. F. Fischer

1959-01-01

16

Laser ablated zirconium plasma: A source of neutral zirconium  

NASA Astrophysics Data System (ADS)

The authors report spectroscopic investigations of laser produced zirconium (Zr) plasma at moderate laser fluence. At low laser fluence the neutral zirconium species are observed to dominate over the higher species of zirconium. Laser induced fluorescence technique is used to study the velocity distribution of ground state neutral zirconium species. Two-dimensional time-resolved density distributions of ground state zirconium is mapped using planner laser induced fluorescence imaging and total ablated mass of neutral zirconium atoms is estimated. Temporal and spatial evolutions of electron density and temperature are discussed by measuring Stark broadened profile and ratio of intensity of emission lines, respectively.

Yadav, Dheerendra; Thareja, Raj K.

2010-10-01

17

Preparation of zirconium boride  

Microsoft Academic Search

1.It is shown that zirconium boride of the stoichiometric,composition, containing an insignificant amount of impurities, can be produced from commercially-pure starting materials (B4C, ZrO2).2.A study was made of the influence exerted by the chemical composition and particle size of the starting boron carbide on the chemical and phase compositions of the resultant zirconium boride.As in the case of titanium boride

V. F. Funke; S. I. Yudkovskii

1964-01-01

18

Phosphinomethyl complexes of zirconium  

SciTech Connect

The synthesis, structure, and reactivity of a new class of early transition metal complexes containing a phosphinomethyl ligand are described. These complexes possess two different sites of reactivity: the zirconium metal center and the remote phosphine moiety. Phosphinomethyl complexes of zirconium are the first examples of such complexes containing either a group IV or V metal displaying exclusively monohapto bonding between ligand and metal. Zirconcene halides can be selectively mono- or bis-substituted with the appropriate dialkylphosphinomethylithium reagent. The steric and electronic properties of these complexes can be altered by modifying several moieties in the molecule. The intramolecular disposition of the remote functionality can be exploited to stabilize the unusual +3 oxidation state of zirconium. The isolation and characterization of a monomeric paramagnetic phosphinomethyl zirconocene(III) complex has opened the way for a systematic study of the heretofore inaccessible zirconium(III) system. The remote phosphine moiety can also be exploited in an intermolecular manner to construct novel heterobimetallic compounds. These include simple acyclic bridged species as well as a remarkably hindered cyclic complex. Phosphinomethyl complexes of zirconium are unique because they have a remote phosphine moiety which is free to interact in either an inter- or intramolecular fashion. The most important ramifications of this for organic synthesis or catalysis are the stabilization of an unusual monomeric zirconium(III) oxidation state, and the ability to complex a second transition metal to form heterobimetallic complexes.

Young, S.J.

1985-01-01

19

Corrosion of zirconium boride and zirconium boron nitride coated steels  

Microsoft Academic Search

The corrosion behaviour of sputtered zirconium boride and zirconium boron nitride coatings on carbon steel substrates was investigated. Coatings were produced employing non-reactive as well as reactive d.c. magnetron sputtering deposition using zirconium diboride targets. The copper decoration technique was used to make visible the types of coating defects and their distribution. To quantify the corrosion behaviour, potentiodynamic polarization measurements

M. Ürgen; A. F. Çakir; O. L. Eryilmaz; C. Mitterer

1995-01-01

20

Zirconium diboride low resistance layers  

Microsoft Academic Search

The ion-plasma sputtering method, as we see it, is perspective for the zirconium diboride thin films production. The literature sources on the zirconium diboride thin films growth characteristics are sparse. The goal of this paper is to investigate the possibility of the zirconium diboride thin films production with the magnetron sputtering method and to investigate its structure and physical properties

A. F. Andreeva; V. M. Statsenko; L. A. Klotchkov

1997-01-01

21

Zirconium in the nuclear industry  

SciTech Connect

This book contains over 40 selections. Some of the titles are: Zirconium-Barrier Cladding Attributes; Recent Studies of Crack Initiation During Stress Corrosion Cracking of Zirconium Alloys; Oxidation of Zircaloy-4 in Steam at 1300 to 2400/sup 0/C; and Residual Stresses in Textured Zirconium Alloys.

Adamson, R.B.; Van Swam, L.F.P.

1987-01-01

22

Thermal and related studies of some basic zirconium salts  

Microsoft Academic Search

Studies of basic zirconium carbonate, oxalate, nitrate and sulphate using TG, DTA and DTG methods, combined with isothermal gaseous product analyses, IR spectroscopy and X-ray diffraction techniques, have shown that the ease of ligand removal from such salts follows the sequence: ‘loosely bound’ H2O>CO32?? C2O42?>NO3?>OH? (or ‘ tightly bound’ H2O)>SO42?.

F. G. R. Gimblett; A. Hussain; K. S. W. Sing

1988-01-01

23

Dibarium zirconium tetraoxalate trihydrate.  

PubMed

A new mixed barium zirconium oxalate, triaquatetra-mu-oxalato-dibarium(II)zirconium(IV), Ba(2)Zr(C(2)O(4))(4).3H(2)O or [Ba(2)Zr(C(2)O(4))(4)(H(2)O)(3)](n), has been synthesized. The complex is built from eightfold-coordinated Zr atoms and eleven- and sixfold-coordinated Ba atoms, linked by oxalate groups. The Zr atom, the two Ba atoms and one water O atom lie on crystallographic twofold axes, so that each coordination polyhedron has imposed C2 symmetry. Packing in the crystal is also assumed through hydrogen bonds. PMID:15178833

Vertruyen, Bénédicte; Robertz, Bénédicte; Guillaume, Bernard; Rulmont, André; Spirlet, Marie Rose

2004-06-01

24

Dopaminium nitrate  

PubMed Central

The asymmetric unit of the title salt [systematic name: 2-(3,4-di­hydroxy­phen­yl)ethanaminium nitrate], C8H12NO2 +·NO3 ?, contains two independent cations and two independent nitrate anions. The crystal structure consists of discrete nitrate ions stacked in layers parallel to (010). These layers are linked via the dopaminium cations by O—H?O, N—H?O and weak C—H?O hydrogen bonds, forming a three-dimensional supra­molecular network.

Gatfaoui, Sofian; Marouani, Houda; Roisnel, Thierry; Dhaouadi, Hassouna

2014-01-01

25

Electroless deposition process for zirconium and zirconium alloys  

DOEpatents

A method is disclosed for preventing stress corrosion cracking or metal embrittlement of a zirconium or zirconium alloy container that is to be coated on the inside surface with a layer of a metal such as copper, a copper alloy, nickel, or iron and used for holding nuclear fuel material as a nuclear fuel element. The zirconium material is etched in an etchant solution, desmutted mechanically or ultrasonically, oxidized to form an oxide coating on the zirconium, cleaned in an aqueous alkaline cleaning solution, activated for electroless deposition of a metal layer and contacted with an electroless metal plating solution. This method provides a boundary layer of zirconium oxide between the zirconium container and the metal layer. 1 fig.

Donaghy, R.E.; Sherman, A.H.

1981-08-18

26

Electroless deposition process for zirconium and zirconium alloys  

DOEpatents

A method is disclosed for preventing stress corrosion cracking or metal embrittlement of a zirconium or zirconium alloy container that is to be coated on the inside surface with a layer of a metal such as copper, a copper alloy, nickel, or iron and used for holding nuclear fuel material as a nuclear fuel element. The zirconium material is etched in an etchant solution, desmutted mechanically or ultrasonically, oxidized to form an oxide coating on the zirconium, cleaned in an aqueous alkaline cleaning solution, activated for electroless deposition of a metal layer and contacted with an electroless metal plating solution. This method provides a boundary layer of zirconium oxide between the zirconium container and the metal layer.

Donaghy, Robert E. (Wilmington, NC); Sherman, Anna H. (Wilmington, NC)

1981-01-01

27

Plasma arc melting of zirconium  

SciTech Connect

Zirconium, like some other refractory metals, has an undesirable sensitivity to interstitials such as oxygen. Traditionally, zirconium is processed by electron beam melting to maintain minimum interstitial contamination. Electron beam melted zirconium, however, does not respond positively to mechanical processing due to its large grain size. The authors undertook a study to determine if plasma arc melting (PAM) technology could be utilized to maintain low interstitial concentrations and improve the response of zirconium to subsequent mechanical processing. The PAM process enabled them to control and maintain low interstitial levels of oxygen and carbon, produce a more favorable grain structure, and with supplementary off-gassing, improve the response to mechanical forming.

Tubesing, P.K.; Korzekwa, D.R.; Dunn, P.S.

1997-12-31

28

Zirconium for superior corrosion resistance  

SciTech Connect

Zirconium is a transition element located along with sister elements titanium and hafnium in Group IVB of the periodic table. It is grayish white metal, with a density somewhat less than carbon steel. Zirconium is the ninth most common metallic element in the earth`s crust, and is more abundant than zinc, lead, nickel, or even copper. Zirconium is exceptionally resistant to corrosion by many common acids and alkalis. It is resistant to most organic acids, such as formic, acetic, lactic, and oxalic acids. It also has a high resistance to localized forms of corrosion, such as pitting, crevice corrosion, and stress corrosion cracking. Its corrosion resistance is caused by the formation of a dense, tenaciously adherent, chemically inert oxide film on the surface. This oxide film protects the base metal from both chemical and mechanical attack at temperatures up to about 400 C (750 F). This article describes zirconium`s formability, machinability, corrosion resistance, and several typical applications.

Bird, K.W. [SPF Corp. of America, Louisville, CO (United States); Richardson, K. [Wah Chang, Albany, OR (United States)

1997-03-01

29

PREPARATION OF PURE ANHYDROUS ZIRCONIUM FLUORIDE  

Microsoft Academic Search

The preparation of pure and anhydrous (with hafnium) zirconium fluoride ; was studied on a laboratory scale. The starting material was zirconium oxide. ; Ammonium acid fluoride was used as the fluorinating agent. Ammonium ; fluozirconate was transformed to zirconium fluoride by heating in a vacuum. The ; zirconium fluoride was purified by sublimation at 700 deg in a vacuum.

C. Decroly; D. Tytgat; J. Gerard

1957-01-01

30

Preparation of zirconium diboride  

Microsoft Academic Search

1.X-ray and microstructural analyses show that zirconium diboride powder obtained in industrial plants by boron carbide reduction in hydrogen at 1800°C contains about 4.94±0.12% ZrB12.2.A uniphase product (ZrB2) can be obtained by boron carbide reduction below 1650°, which is the lower limit of temperature stability of ZrB12 [16], or at higher temperatures, followed by slow cooling in the range 1650–1400°C.3.The

M. A. Kuzenkova; P. S. Kislyi

1965-01-01

31

21 CFR 181.33 - Sodium nitrate and potassium nitrate.  

Code of Federal Regulations, 2010 CFR

...2009-04-01 true Sodium nitrate and potassium nitrate. 181.33 Section 181.33 Food...Ingredients § 181.33 Sodium nitrate and potassium nitrate. Sodium nitrate and potassium nitrate are subject to prior sanctions...

2010-01-01

32

21 CFR 181.33 - Sodium nitrate and potassium nitrate.  

Code of Federal Regulations, 2010 CFR

...2009-04-01 false Sodium nitrate and potassium nitrate. 181.33 Section 181.33 Food...Ingredients § 181.33 Sodium nitrate and potassium nitrate. Sodium nitrate and potassium nitrate are subject to prior sanctions...

2009-04-01

33

21 CFR 181.33 - Sodium nitrate and potassium nitrate.  

Code of Federal Regulations, 2013 CFR

...2013-04-01 false Sodium nitrate and potassium nitrate. 181.33 Section 181.33 Food...Ingredients § 181.33 Sodium nitrate and potassium nitrate. Sodium nitrate and potassium nitrate are subject to prior sanctions...

2013-04-01

34

Zirconium extraction into octyl(phenyl)-N,N-diisobutylcarbamoylmethyl phosphine oxide and tributyl phosphate  

SciTech Connect

Classical slope analysis techniques were used to determine the octyl(phenyl)-N,N-diisobutylcarbamoylmethyl phosphine oxide (CMPO) and nitrate stoichiometries for the extraction of zirconium by CMPO diluted with diisopropylbenzene (DIPB). The equilibrium constant for the extraction of zirconium by CMPO was also determined using classical slope analysis techniques. The extraction of zirconium by TBP in n-dodecane was used as a control to verify the zirconium species as Zr{sup +4}, and to verify the experimental methodology. Equilibrium [CMPO]{sub org} and [TBP]{sub org} concentrations were determined by accounting for the extraction of HNO{sub 3} into both TBP and CMPO solvents. Nitric acid dissociation and aqueous phase activity coefficients were also taken into consideration. Organic activity coefficients, Zr{sup +4} activity coefficients, Zr{sup +4} hydrolysis, and consumption of TBP or CMPO by water were neglected. Nitrate and CMPO dependencies for the extraction of zirconium have been determined from this work to be: Zr{sub aq}{sup +4} + 4 NO{sub 3 aq}{sup {minus}} + 2 CMPO{sub org} {r_arrow} Zr(NO{sub 3}){sub 4} {sm_bullet} 2 CMPO{sub org}. An equilibrium constant of 1.13 {times} 10{sup 5} {+-} 1.48 {times} 10{sup 4} at 25 C was also determined for this reaction.

Brewer, K.N.; Herbst, R.S.; Todd, T.A.; Christian, J.D. [Lockheed Idaho Technologies Co., Idaho Falls, ID (United States)

1998-07-01

35

Synthesis and characterization of zirconium-doped mesoporous nano-crystalline TiO2  

Microsoft Academic Search

A series of zirconium-doped nano-titania (Zr\\/TiO2) with various amounts of Zr were prepared by sol-gel method using titanium(iv) isopropoxide and zirconium nitrate as precursors. Zr\\/TiO2 samples were characterized using X-ray diffraction (XRD), surface area-pore volume measurements, infrared (FTIR) spectroscopy, UV-vis-diffuse reflectance spectroscopy (UV-vis-DRS), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, thermogravimetric (TG) analysis, and transmission electron microscopy (TEM) techniques. XRD data

Kanattukara Vijayan Bineesh; Dong-Kyu Kim; Dae-Won Park

2010-01-01

36

Synthesis, characterization and optical properties of novel N donor ligands-chelated zirconium(IV) complexes  

NASA Astrophysics Data System (ADS)

Novel zirconium complexes have been synthesized by using a mixture of zirconium nitrate, 1,2,4,5-benzen tetracarboxylic acid (H4btec), 1,10-phenanthroline(phen) and potassium thiocyanate. Monodentate coordination mode of btec acid for all complexes was investigated by FT-IR spectroscopy. The complexes were also characterized by UV-Vis, 1H NMR, CHN, ICP-AES. The reaction details and features were described and discussed. The photoluminescence emission of seven zirconium complexes was shown two series peaks: first, sharp and intense bands from 300 to 500 nm and broadened with less intensity from 650 to 750 nm for the second bands. Each of the zirconium compounds were doped in PVK:PBD blend as host. The ratio of zirconium complexes for each type were modified 8 wt.% in PVK:PBD(100:40). The electroluminescence spectra of zirconium complexes were indicated a red shift rather than PVK:PBD blend. We suggest that the electroplex occurring at PVK-Zr complex interface.

Shahroosvand, Hashem; Nasouti, Fahimeh; Mohajerani, Ezeddin; Khabbazi, Amir

2012-11-01

37

Method of Etching Zirconium Diboride.  

National Technical Information Service (NTIS)

The invention described herein may be manufactured, used, and licensed by or for the Government for governmental purposes without the payment to us of any royalty thereon. This invention relates in general to a method of etching zirconium diboride, zircon...

L. S. Heath B. Kwiatkowski

1988-01-01

38

Method for Collecting Zirconium Tetrachloride.  

National Technical Information Service (NTIS)

A neutron-irradiated nuclear fuel composition containing zirconium and a nuclear fuel selected from uranium and plutonium is treated by hydrochlorination of the composition with gaseous hydrogen chloride at from 350 to 800 degrees C. to selectively volati...

T. A. Gens

1965-01-01

39

Environmentally Friendly Zirconium Oxide Pretreatment.  

National Technical Information Service (NTIS)

Pretreatments based on zirconium oxide are being used commercially in automotive and other industrial operations as replacements to hexavalent chromium-based and zinc phosphate pretreatments. This report describes work to document the performance of comme...

J. L. Stalker N. J. Silvernail T. Lingenfelter

2013-01-01

40

Comminution characteristics of zirconium diboride  

Microsoft Academic Search

1.The investigation into the comminution kinetics of zirconium diboride powder has demonstrated that comminution is more effective in a vibratory mill than in a ball mill. The optimum comminution time is 2–3 h.2.Tsyurupa's analytical method of calculation can be employed for determining the particle-size distribution of powders.3.Of the dispersing media investigated, ethyl alcohol gives the most agglomeration-resistant zirconium diboride suspensions.4.Of

L. V. D'yakonova; P. S. Kislyi

1972-01-01

41

Methyl Cellulose Nitrate.  

National Technical Information Service (NTIS)

Methyl cellulose nitrate was prepared by nitration of methyl cellulose with 98% nitric acid dissolved in methylene chloride and, in 98% nitric acid without a solvent. With both procedures nitration is apparently complete within fifteen minutes. The hetero...

J. Bobinski Y. P. Carignan

1967-01-01

42

Spectrophotometric Determination of Zirconium with Xylenol Orange.  

National Technical Information Service (NTIS)

High purity hydride forming metal films are used as hydrogen isotope occluders and function as electrodes in neutron generator tubes. This use of zirconium occluder films requires reliable analytical methods for routine determination of the zirconium film...

R. J. Antepenko

1982-01-01

43

Ablation Resistant Zirconium and Hafnium Ceramics  

NASA Technical Reports Server (NTRS)

High temperature ablation resistant ceramic composites have been made. These ceramics are composites of zirconium diboride and zirconium carbide with silicon carbide, hafnium diboride and hafnium carbide with silicon carbide and ceramic composites which contain mixed diborides and/or carbides of zirconium and hafnium. along with silicon carbide.

Bull, Jeffrey (Inventor); White, Michael J. (Inventor); Kaufman, Larry (Inventor)

1998-01-01

44

Dissolution of Zirconium in Titanium Equipment.  

National Technical Information Service (NTIS)

The method of dissolving zirconium salts in a titanium container system is useful in the nuclear reactor field. The zirconium is reacted with zirconium dissolvent consisting of a 2 to 6 molar aqueous solution of nitric acid containing total fluoride not e...

W. E. Clark T. A. Gens

1965-01-01

45

Nanolithography on Zirconium Surfaces  

NASA Astrophysics Data System (ADS)

We report, for the first time, scanning probe nanolithography on single crystal zirconium (Zr) surfaces using an atomic force microscope (AFM) tip in air. Preliminary experiments indicate that the size of the nanostructures written on Zr is 50 - 100 nm with applied DC voltages of 1 - 25 V and exposure times in the range of 1 - 60 seconds. We study the dependence of the size of the nanostructures on the magnitude of the applied voltage and current through the Zr substrate. This allows us to compare the results of SPM lithography on Zr with those on Si. Apparently, the nature of the current in these two cases is different. The current during high voltage Si oxidation exhibits Ohmic behavior and can reach 300 microamps. We believe that this current is the result of electrical breakdown in the meniscus of water resulting in conductivity dominated by electron mobility. In the case of Zr, the magnitude of the DC current is very small (less than 1 microamp) and exhibits typical Faradic behavior related with the transport of hydroxyl ions from an AFM tip down to the Zr surface. Lithographic oxidation of Zr surfaces is a very promising step toward the development of a comprehensive description of the nanolithographic process and complements our efforts to prepare Zr surfaces with novel properties via hyperthermal chemical reaction pathways.

Farkas, Natalia; Lyuksyutov, Sergei F.; Ramsier, Rex D.

2002-04-01

46

Transformation superplasticity of zirconium  

SciTech Connect

A tensile strain of 270% was achieved for coarse-grained zirconium subjected to transformation superplasticity condition, where strain increments are accumulated upon repeated thermal cycling around the allotropic transformation temperature under the biasing effect of a uniaxial tensile stress. The strain increment per cycle was found to consist of two equal contributions from transformations on heating and cooling and to increase linearly with the applied stress. The measured strain increments are in good quantitative agreement with predictions based on the average internal stress during the transformation, which was determined independently from experimental transformation times. As the cycling frequency is raised, the average strain rate increases (a maximum value of 1.3 {times} 10{sup {minus}4} s{sup {minus}1} was measured), but the strain increment per cycle decreases above a critical cycling frequency, for which the sample gage section undergoes only a partial phase transformation. The resulting reduction in internal mismatch and increase in internal stress are modeled using the experimental observation that {beta}-Zr deforms by a mixture of diffusional and dislocation creep in the stress range of interest.

Zwigl, P. [Massachusetts Inst. of Tech., Cambridge, MA (United States). Dept. of Materials Science and Engineering; Dunand, D.C. [Northwestern Univ., Evanston, IL (United States). Dept. of Materials Science and Engineering

1998-10-01

47

Mössbauer spectroscopy of zirconium alloys  

NASA Astrophysics Data System (ADS)

Mössbauer investigations of zirconium alloys were examined. Data about the chemical state of iron atoms in the zirconium alloys of different composition has been provided. Mössbauer spectroscopy revealed that small quantities of iron in binary zirconium alloy are in the solid solution ?-Zr (up to 0.02 wt.%). Different iron atoms concentration and thermo-mechanical treatments may lead to formation the intermetallic compounds Zr3Fe, Zr2Fe, ZrFe2. Adding tin atoms does not affect the formation and shape of Mössbauer spectra of these compounds. Adding Cr and Nb atoms makes significant changes in the shape of Mössbauer spectra and leads to the formation of complex intermetallic compounds. Adding Cu and W atoms, the shape of the binary alloys spectra (Zr-Fe) remains unchanged, but a change in the temperature dependence behavior of the spectral parameters occurs and also, changes to the properties of the alloys.

Filippov, V. P.; Bateev, A. B.; Lauer, Yu. A.; Kargin, N. I.

2013-04-01

48

Eutectic structure in zirconium electrocorundum  

SciTech Connect

The authors explain the eutectic structure of zirconium electrocorundum, with the goal of controlling crystallization of actual alloys by changing the melt cooling conditions to produce materials of assigned properties. Sample chemical composition and conditions of preparation are shown. A qualitative change in structure of hypoeutectic alloys of Al/sub 2/O/sub 3/ with zRO/sub 2/ (zirconium electrocorundum) is possible only under conditions where the formation mechanism of corundum crystals changes, and the fresh branched growth of crystals composing the eutectic is disrupted. Nucleation of a regular eutetic struscure in zirconium electrocorundum is observed for the case of melt crystallization far from eutectic composition on abrupt melt cooling at the mold boundary and for the case of low-frequency melt vibration.

Zhekhanova, N.B.; Fotiev, A.A.; Gladkov, V.E.

1986-09-01

49

EFFECTS OF ZIRCONIUM ON THE GROWTH AND PHOTOSYNTHETIC PIGMENT COMPOSITION OF CHLORELLA PYRENOIDOSA GREEN ALGAE  

Microsoft Academic Search

The effects of zirconium (Zr) were investigated on the growth rate, dry matter accumulation, and elemental and photosynthetic pigment composition of Chlorella pyrenoidosa green algae. Algae were treated with 0.1–50 ?M (? 0.009–4.561 mg dm) of Zr; inorganic compounds (Zr oxychloride, Zr nitrate) and organic chelates (Zr ascorbate or Zr citrate) were applied. All Zr compounds displayed only a slight

László Simon; Marietta Fodor; István Pais

2001-01-01

50

Nano-zirconium oxide and nano-silver oxide\\/cotton gauze fabrics for antimicrobial and wound healing acceleration  

Microsoft Academic Search

Nano-zirconium-oxide (nano-Zr-oxide) and nano-silver-oxide (nano-Ag-oxide) were in situ synthesized and deposited into cotton gauze fabrics by reduction of zirconium oxychloride or silver nitrate solutions, in the presence of fabric samples using sodium hydroxide-hydrogen peroxide mixture solution at pH 9.5. The resulted homogenous distribution of nano-Zr-oxide and nano-Ag-oxide inside the fabric were characterized by scanning electron microscopy coupled with energy dispersive

Mohamed Gouda

2012-01-01

51

Mechanisms of nitrate tolerance  

Microsoft Academic Search

There is now little dispute that clinical tolerance of organic nitrates occurs, particularly when these drugs are used by themselves to treat patients with stable angina pectoris and congestive heart failure. Classical hypotheses of nitrate tolerance suggest the phenomenon to result from vascular depletion of critical sulfhydryl groups, which are necessary to bring about vasorelaxation from nitrates. While this mechanism

Ho-Leung Fung; John Anthony Bauer

1994-01-01

52

Systems zirconium-chromium-aluminum and zirconium-copper-aluminum  

Microsoft Academic Search

The systems Zr-Cr-A1 and Zr-Cu-A1 were investigated using alloys prepared in an electric arc furnace with a purified argon atmosphere, by melting starting charges (with allowance for possible losses of volatile components) composed of iodide-grade zirconium (99.9%), electrolytic chromium (99.9%), electrolytic copper (99o99%), and AV-000 aluminum (99.97%). Spot chemical analyses and weight determinations established that the loss of aluminum or

V. Ya. Markiv; V. V. Burnashova

1970-01-01

53

Reactive hot pressing of zirconium diboride  

Microsoft Academic Search

The reaction of zirconium and boron was investigated as a potential route to form dense monolithic zirconium diboride (ZrB2) ceramics. Attrition milling of the precursors produced nanosized (less than 100nm) zirconium metal particles that reacted with boron to form ZrB2 with an average particle size of less than 100nm at temperatures as low as 600°C. Scanning electron microscopy of ZrB2

Adam L. Chamberlain; William G. Fahrenholtz; Gregory E. Hilmas

2009-01-01

54

Spectrophotometric titration of zirconium in siliceous materials.  

PubMed

An accurate and selective complexometric titration procedure based upon a spectrophotometrically detected end-point has been developed for the determination of zirconium in glasses, glass-ceramics and refractories. A p-bromomandelic acid separation step for zirconium imparts excellent selectivity to the procedure. The method is particularly important for the 1-5% concentration range where a simple, accurate and selective method for the determination of zirconium has been lacking. PMID:18962344

Sugawara, K F; Su, Y S; Strzegowski, W R

55

Spectrophotometric determination of zirconium with xylenol orange  

SciTech Connect

High purity hydride forming metal films are used as hydrogen isotope occluders and function as electrodes in neutron generator tubes. This use of zirconium occluder films requires reliable analytical methods for routine determination of the zirconium film weight in a production environment. In this study, a spectrophotometric method was evaluated for the determination of zirconium films. The method is based upon the formation of a highly colored zirconium complex with xylenol orange in a dilute perchloric acid medium. Dilute hydrofluoric acid is used in this procedure to selectively dissolve the zirconium film off the substrate. A perchloric acid fuming step is used to remove hydrofluoric acid from the solution. The zirconium solutions are depolymerized before complex formation by heating in 2 N perchloric acid. The zirconium complex exhibits a maximum absorbance in 0.2 to 0.3 M perchloric acid at a wavelength of 531 nanometers. Beer's law is obeyed for zirconium concentrations through 2.1 parts per million. Molybdenum, at concentrations equal to zirconium, does not interfere with the xylenol orange method.

Antepenko, R.J.

1982-05-14

56

Zirconium in a sulfuric acid pickling application  

SciTech Connect

In 1972, Goodyear discovered that zirconium was an ideal material to construct heating coils for sulfuric acid picking tanks. Recently, localized corrosion and high uniform corrosion were reported with certain zirconium coils. The problems could be attributed to the contamination of chloride and/or fluoride ions. Results of electrochemical and immersion tests are used to discuss the effects of acid concentration and acid impurities, such as iron, chloride and fluoride ions, on zirconium's corrosion properties in H/sub 2/SO/sub 4/. Possible sources for acid impurities are identified. Recommendations are made for steel picking when zirconium equipment is used.

Yau, T.L.

1988-01-01

57

Bacterial adhesion to zirconium surfaces  

Microsoft Academic Search

Zirconium alloys are well-known for their resistance to harsh chemical environments. In the interest of assessing the potential of this class of materials for bio-implant applications, we need to determine if this environmental stability transfers to biological systems. We report on our use of viable counts and infrared spectroscopic techniques to monitor how well thermally processed Zircaloy-2 surfaces resist bacterial

B. W. Buczynski; M. M. Kory; R. P. Steiner; T. A. Kittinger; R. D. Ramsier

2003-01-01

58

Optical properties of zirconium nitride  

SciTech Connect

In this investigation the authors have studied the optical properties of zirconium nitride by the Beattie-Cohn ellipsometric method. The optical properties were studied on an ellipsometric unit over the spectral range 1 eV < E < 5 eV. The dependence of the reflectivity coefficient, the light transmittance, and the real part of the dielectric function were calculated from the results of measuring the optical constants n and kappa as a function of the photon energy.

Atamanenko, B.A.; Belyi, M.U.; Drozd, P.I.; Tsebulya, G.G.; Shaikevich, I.A.

1987-11-01

59

Determination of small amounts of TBP and DBP in uranyl nitrate solutions.  

PubMed

Tri- and dibutylphosphate (TBP and DBP) in concentrated uranyl nitrate solution are determined by a method based on the solvent extraction of zirconium-95. The distribution ratio of zirconium-95 between dilute solutions of TBP and DBP in dodecane and 10M hydrochloric acid and 1Mnitric acid respectively is measured. There is a logarithmic relationship between the distribution ratio and concentration of TBP and DBP, which enables them to be determined rapidly and with an error of +/- 10% over the range 1-100ppm of TBP and 40-600 ppm of DBP. The lower limit is 0.5 ppm for TBP and 10 ppm for DBP. PMID:18960556

Ishimori, T; Ueno, K

1969-05-01

60

Comparison of sodium zirconium phosphate and Synroc matrices for immobilization of high-level waste  

SciTech Connect

The aims of the present work were to investigate possible compatibility between sodium zirconium phosphate (NZP) and Synroc titanate phases, to prepare NZP-based waste forms by hot-pressing rather than sintering, and to investigate the incorporation in NZP of (a) Cs/Sr as simulated heat-generating nuclides; (b) simulated actinides; and (c) simulated Purex waste. The NZP samples were prepared by methods similar to those used for Synroc. The precursor NZP phase was formed from tetrabutyl zirconate Zr(OC{sub 4}H{sub 9}){sub 4}, sodium nitrate, and 85% orthophosphoric acid. Simulated waste nitrate solutions were then mixed with the liquid precursor. After stir drying of the precursor, calcination was carried out at 700{degree}C to remove nitrates and organics.

Zyryanov, V.N. [Inst. of Experimental Mineralogy, Chernogolovka (Russian Federation); Vance, E.R. [Australian Nuclear Science and Technology Organization (ANSTO), Menai (Australia). Materials Division

1996-12-31

61

Cylodextrin Polymer Nitrate  

NASA Technical Reports Server (NTRS)

The development of the use of cyclodextrin nitrates as possible components of insensitive, high-energy energetics is outlined over a time period of 12 years. Four different types of cyclodextrin polymers were synthesized, nitrated, and evaluated regarding their potential use for the military and aerospace community. The synthesis of these novel cyclodextrin polymers and different nitration techniques are shown and the potential of these new materials is discussed.

Kosowski, Bernard; Ruebner, Anja; Statton, Gary; Robitelle, Danielle; Meyers, Curtis

2000-01-01

62

Thermochemical nitrate destruction  

DOEpatents

A method is disclosed for denitrification of nitrates and nitrates present in aqueous waste streams. The method comprises the steps of (1) identifying the concentration nitrates and nitrites present in a waste stream, (2) causing formate to be present in the waste stream, (3) heating the mixture to a predetermined reaction temperature from about 200.degree. C. to about 600.degree. C., and (4) holding the mixture and accumulating products at heated and pressurized conditions for a residence time, thereby resulting in nitrogen and carbon dioxide gas, and hydroxides, and reducing the level of nitrates and nitrites to below drinking water standards.

Cox, John L. (Richland, WA); Hallen, Richard T. (Richland, WA); Lilga, Michael A. (Richland, WA)

1992-01-01

63

Direct synthesis of Zr-SBA-15 mesoporous molecular sieves with high zirconium loading: Characterization and catalytic performance after sulfated  

Microsoft Academic Search

The Zr-SBA-15 mesoporous materials with high Zr\\/Si ratio (0–2.32) were first synthesized directly using zirconium nitrate and tetraethyl orthosilicate as precursor, displaying higher thermal stability after activated at 600°C. 29Si NMR spectra revealed the part existance of ZrO2 in the framework of SBA-15. After sulfated, the SO42-\\/Zr-SBA-15 exhibited high activity in the isomerization of n-pentane at 35°C, and the conversion

Li Fuxiang; Yu Feng; Li Yongli; Li Ruifeng; Xie Kechang

2007-01-01

64

Electrochemical decomposition of complexes of zirconium or hafnium  

Microsoft Academic Search

This patent describes an improvement in a method for separating hafnium from zirconium where a complex of zirconium and hafnium chlorides and phosphorus oxychloride is prepared from zirconium-hafnium chloride and the complex is subjected to a distillation to produce a hafnium chloride enriched stream of complex and a zirconium enriched chloride stream of complex. The improvement comprising: electrochemical breaking the

T. S. Snyder; R. A. Stoltz; D. F. McLaughlin

1989-01-01

65

Hydrogen desorption kinetics from zirconium hydride and zirconium metal in vacuum  

NASA Astrophysics Data System (ADS)

The kinetics of hydrogen desorption from zirconium hydride is important in many nuclear design and safety applications. In this paper, a coordinated experimental and modeling study has been used to explicitly demonstrate the applicability of existing kinetic theories for hydrogen desorption from zirconium hydride and ?-zirconium. A static synthesis method was used to produce ?-zirconium hydride, and the crystallographic phases of the zirconium hydride were confirmed by X-ray diffraction (XRD). Three obvious stages, involving ?-zirconium hydride, a two-phase region, and ?-zirconium, were observed in the hydrogen desorption spectra of two zirconium hydride specimens with H/Zr ratios of 1.62 and 1.64, respectively, which were obtained using thermal desorption spectroscopy (TDS). A continuous, one-dimensional, two-phase moving boundary model, coupled with the zero- and second-order kinetics of hydrogen desorption from ?-zirconium hydride and ?-zirconium, respectively, has been developed to reproduce the TDS experimental results. A comparison of the modeling predictions with the experimental results indicates that a zero-order kinetic model is valid for description of hydrogen flux away from the ?-hydride phase, and that a second-order kinetic model works well for hydrogen desorption from ?-Zr if the activation energy of desorption is optimized to be 70% of the value reported in the literature.

Hu, Xunxiang; Terrani, Kurt A.; Wirth, Brian D.

2014-05-01

66

Solid Solutions in the System Ammonium Nitrate-Potassium Nitrate  

Microsoft Academic Search

BY phase work on the system ammonium nitrate-potassium nitrate-water, Janëcke1,2 showed that below 23° C. two types of solid solution can exist: potassium nitrate dissolved in ammonium nitrate (form III) and ammonium nitrate in potassium nitrate (form II). At higher temperatures there is an increasing amount of another phase which is of a different crystalline form from any of the

R. V. Coates; J. M. Crewe

1961-01-01

67

MODELED WET NITRATE DEPOSITION  

EPA Science Inventory

Modeled data on nitrate wet deposition was obtained from Dr. Jeff Grimm at Penn State Univ. Nitrate wet depostion causes acidification and eutrophication of surface water bodies. See below regarding decriptions on how original data was produced. These data will be part of futur...

68

Spinach Nitrate Reductase 1  

PubMed Central

Initial velocity studies of immunopurified spinach nitrate reductase have been performed under conditions of controlled ionic strength and pH and in the absence of chloride ions. Increased ionic strength stimulated NADH:ferricyanide reductase and reduced flavin:nitrate reductase activities and inhibited NADH:nitrate reductase, NADH:cytochrome c reductase and reduced methyl viologen:nitrate reductase activities. NADH:dichlorophenolindophenol reductase activity was unaffected by changes in ionic strength. All of the partial activities, expressed in terms of micromole 2 electron transferred per minute per nanomole heme, were faster than the overall full, NADH:nitrate reductase activity indicating that none of the partial activities included the rate limiting step in electron transfer from NADH to nitrate. The pH optimum for NADH:nitrate reductase activity was determined to be 7 while values for the various partial activities ranged from 6.5 to 7.5. Chlorate, bromate, and iodate were determined to be alternate electron acceptors for the reduced enzyme. These results indicate that unlike the enzyme from Chlorella vulgaris, intramolecular electron transfer between reduced heme and Mo is not rate limiting for spinach nitrate reductase.

Barber, Michael J.; Notton, Brian A.

1990-01-01

69

Nitrite and Nitrate Pharmacokinetics.  

National Technical Information Service (NTIS)

Elimination kinetics of nitrite and nitrate in the canine, ovine, and equine were determined. The elimination half-life of nitrite was found to be 30.0, 28.5 and 33.9 minutes in the canine, ovine and equine, respectively; that of nitrate was 44.68, 4.23 a...

N. R. Schneider R. A. Yeary

1975-01-01

70

Method of etching zirconium diboride  

SciTech Connect

The invention described herein may be manufactured, used, and licensed by or for the Government for governmental purposes without the payment to us of any royalty thereon. This invention relates in general to a method of etching, zirconium diboride(ZrB/sub 2/) and, in particular, to a method of dry etching a thin film of ZrB/sub 2/ that has been deposited onto a substrate and patterned using photolithography. U.S. patent application S.N. 156, 124, filed 16 February, 1988, of Linda S. Heath for Method of Etching Titanium Diboride and assigned to a common assignee and with which this application is copending describes and claims a method of etching titanium diboride with a dry etch. Zirconium diboride, like titanium diboride, TiB/sub 2/, has become of interest in laboratory research because of its resistance to change or degradation at high temperatures. By adjusting the process parameters, one is able to attain etch rates of 67 to 140 A/min for ZrB/sub 2/. This is useful for patterning ZrB/sub 2/ as a diffusion barrier or a Schottky contact to semiconductors. The ZrB/sub 2/ film may be on a GaAs substrate.

Heath, L.S.; Kwiatkowski, B.

1988-03-31

71

Nitrate reduction by metallic iron  

Microsoft Academic Search

Chemical reduction of nitrate by metallic iron (Fe0) was studied as a potential technology to remove nitrate from water. The effects of pH and the iron-to-nitrate ratio on both nitrate reduction rate and percent removal were investigated. Rate constants and the apparent reaction order with respect to nitrate were determined and a mass balance was obtained. Rapid nitrate reduction by

Chin-Pao Huang; Hung-Wen Wang; Pei-Chun Chiu

1998-01-01

72

Synthesis of zirconium diboride–zirconium nitride composite powders by self-propagating high-temperature synthesis  

Microsoft Academic Search

Formation of zirconium diboride–zirconium nitride composite powders by self propagating high temperature reaction of zirconium,\\u000a boron and hexagonal boron nitride powders was investigated. Zirconium diboride–zirconium nitride powder mixtures with varying\\u000a proportions were produced by changing the amount of boron nitride in the reactants. Products were subjected to powder X-ray\\u000a diffraction analysis; and grain size and morphology was examined by scanning

H. E. Çamurlu; F. Maglia

2007-01-01

73

Preparation of technical zirconium diboride by the carbothermic reduction of mixtures of zirconium and boron oxides  

Microsoft Academic Search

A study was made of the preparation of technical zirconium diboride by the reduction of mixtures of zirconium and boron oxides with carbon under industrial conditions. It is shown that the optimum conditions for the preparation of zirconium diboride by the carbothermic method are established when a charge having the composition ZrO2+1.2 B2O3+5 C (i.e., with a 20% excess of

A. I. Karasev

1973-01-01

74

Thermodynamics and kinetics of the sorption of copper ions by hydrated zirconium oxide  

SciTech Connect

On the basis of an investigation of the influence of the temperature on the equilibrium and kinetics of the sorption of copper ions from ammonium nitrate solution by hydrated zirconium oxide, estimates have been made of the thermodynamic functions describing this process, and calculations have been made of the effective diffusion coefficients of the copper and the apparent activation energy. It has been established that the selective absorption of the copper is dictated by the entropy increase of the system - at positive values of the enthalpy change - and the rate of the process is limited by internal diffusion.

Semenov, M.I.; Blokhin, A.A.; Taushkanov, V.P.

1986-10-20

75

Bioactivation of organic nitrates and the mechanism of nitrate tolerance.  

PubMed

Organic nitrates, such as nitroglycerin, are commonly used in the therapy of cardiovascular disease. Long-term therapy with these drugs, however, results in the rapid development of nitrate tolerance, limiting their hemodynamic and anti-ischemic efficacy. In addition, nitrate tolerance is associated with the expression of potentially deleterious modifications such as increased oxidative stress, endothelial dysfunction, and sympathetic activation. In this review we discuss current concepts regarding the mechanisms of organic nitrate bioactivation, nitrate tolerance, and nitrate-mediated oxidative stress and endothelial dysfunction. We also examine how hydralazine may prevent nitrate tolerance and related endothelial dysfunction. PMID:19130411

Klemenska, Emila; Beresewicz, Andrzej

2009-01-01

76

Decomposition of Four Ammonium Nitrate Propellants.  

National Technical Information Service (NTIS)

The biodegradability of four ammonium nitrate propellants, trimethylammonium nitrate (TMAN), isopropylammonium nitrate (IPAN), triethanolammonium nitrate (TEAN), and hydroxylammonium nitrate (HAN) was assessed in batch and continuous cultures under a vari...

D. L. Kaplan D. J. Emerson P. A. Riley A. M. Kaplan

1983-01-01

77

Penta-zirconium copper tribismuth.  

PubMed

Penta-zirconium copper tribismuth, Zr5CuBi3, crystallizes in the hexa-gonal Hf5CuSn3 structure type. The asymmetric unit contains two Zr sites (site symmetries 3.2 and m2m), one Cu site (site symmetry 3.m) and one Bi site (site symmetry m2m). The environment of the Bi atoms is a tetra-gonal anti-prism with one added atom and a coordination number (CN) of 9. The polyhedron around the Zr1 atom is a defective cubo-octa-hedron with CN = 11. The bicapped hexa-gonal anti-prism (CN = 14) is typical for Zr2 atoms. The Cu atom is enclosed in a eight-vertex polyhedron (octa-hedron with two centered faces). The metallic type of bonding was indicated by an analysis of the inter-atomic distances and electronic structure calculation data. PMID:24109256

Balinska, Agnieszka; Tarasiuk, Ivan; Pavlyuk, Volodymyr

2013-01-01

78

Penta-zirconium copper tribismuth  

PubMed Central

Penta­zirconium copper tribismuth, Zr5CuBi3, crystallizes in the hexa­gonal Hf5CuSn3 structure type. The asymmetric unit contains two Zr sites (site symmetries 3.2 and m2m), one Cu site (site symmetry 3.m) and one Bi site (site symmetry m2m). The environment of the Bi atoms is a tetra­gonal anti­prism with one added atom and a coordination number (CN) of 9. The polyhedron around the Zr1 atom is a defective cubo­octa­hedron with CN = 11. The bicapped hexa­gonal anti­prism (CN = 14) is typical for Zr2 atoms. The Cu atom is enclosed in a eight-vertex polyhedron (octa­hedron with two centered faces). The metallic type of bonding was indicated by an analysis of the inter­atomic distances and electronic structure calculation data.

Balinska, Agnieszka; Tarasiuk, Ivan; Pavlyuk, Volodymyr

2013-01-01

79

Ageing of zirconium alloy components  

NASA Astrophysics Data System (ADS)

India has two types (pressurized heavy water reactors (PHWRs) and boiling water reactors (BWRs)) of commercial nuclear reactors in operation, in addition to research reactors. Many of the life limiting critical components in these reactors are fabricated from zirconium alloys. The progressive degradation of these components caused by the cumulative exposure of high energy neutron irradiation with increasing period of reactor operation was monitored to assess the degree of ageing. The components/specimens examined included fuel element claddings removed from BWRs, pressure tubes and garter springs removed from PHWRs and calandria tube specimens used in PHWRs. The tests included tension test (for cladding, garter spring), fracture toughness test (for pressure tube), crush test (for garter spring), and measurement of irradiation induced growth (for calandria tube). Results of various tests conducted are presented and applications of the test results are elaborated for residual life estimation/life extension of the components.

Chatterjee, S.; Shah, Priti Kotak; Dubey, J. S.

2008-12-01

80

Resistance Butt Welding of Zirconium Alloy Material  

Microsoft Academic Search

Zirconium alloy is the main structural material used in the nuclear fuel production. This material has distinct advantages like less thermal neutron absorption cross-section and better chemical and mechanical properties for the reactor-working conditions. This material is widely used in boiling water and heavy water type reactors. Natural Uranium Dioxide (UO2) pellets are loaded into thin wall zirconium alloy tubes

D. S. Setty; Reddy P. Ravinder; A. L. N. Murthy

2008-01-01

81

Electrochemical decomposition of complexes of zirconium or hafnium  

SciTech Connect

This patent describes an improvement in a method for separating hafnium from zirconium where a complex of zirconium and hafnium chlorides and phosphorus oxychloride is prepared from zirconium-hafnium chloride and the complex is subjected to a distillation to produce a hafnium chloride enriched stream of complex and a zirconium enriched chloride stream of complex. The improvement comprising: electrochemical breaking the zirconium or hafnium chloride complex from the distillation in a chloride or fluoride and chloride molten salt bath to produce the metal or a chloride oof zirconium or hafnium.

Snyder, T.S.; Stoltz, R.A.; McLaughlin, D.F.

1989-09-12

82

Burning of hydroxylammonium nitrate  

Microsoft Academic Search

Burning of solid crystalline hydroxylammonium nitrate (HAN) and its water solutions is studied in a constant-pressure bomb\\u000a within the pressure range from 0.1 to 36 MPa. Abnormally high pressure exponents are found to be typical of combustion of\\u000a the crystalline substance, its ?9-mole\\/liter water solution, and a solution containing ethanolamine nitrate as a fuel: for\\u000a pressures below ?10 MPa, the

B. N. Kondrikov; V. É. Annikov; V. Yu. Egorshev; L. T. De Luca

2000-01-01

83

Investigation of a Cell Design for Electrowinning Zirconium Metal from Zirconium Tetrachloride.  

National Technical Information Service (NTIS)

A cell concept adaptable to the large-scale electrowinning of zirconium metal from zirconium tetrachloride was investigated. Tests were made in twin cells, each 12-in-diam by 33-in long. Electrowinning was performed in one chamber from which the electroly...

G. M. Martinez D. E. Shanks J. R. Woodyard M. M. Wong

1976-01-01

84

ZIRCONIUM OXIDE NANOSTRUCTURES PREPARED BY ANODIC OXIDATION  

SciTech Connect

Zirconium oxide is an advanced ceramic material highly useful for structural and electrical applications because of its high strength, fracture toughness, chemical and thermal stability, and biocompatibility. If highly-ordered porous zirconium oxide membranes can be successfully formed, this will expand its real-world applications, such as further enhancing solid-oxide fuel cell technology. Recent studies have achieved various morphologies of porous zirconium oxide via anodization, but they have yet to create a porous layer where nanoholes are formed in a highly ordered array. In this study, electrochemical methods were used for zirconium oxide synthesis due to its advantages over other coating techniques, and because the thickness and morphology of the ceramic fi lms can be easily tuned by the electrochemical parameters, such as electrolyte solutions and processing conditions, such as pH, voltage, and duration. The effects of additional steps such as pre-annealing and post-annealing were also examined. Results demonstrate the formation of anodic porous zirconium oxide with diverse morphologies, such as sponge-like layers, porous arrays with nanoholes ranging from 40 to 75 nm, and nanotube layers. X-ray powder diffraction analysis indicates a cubic crystallographic structure in the zirconium oxide. It was noted that increased voltage improved the ability of the membrane to stay adhered to the zirconium substrate, whereas lower voltages caused a propensity for the oxide fi lm to fl ake off. Further studies are needed to defi ne the parameters windows that create these morphologies and to investigate other important characteristics such as ionic conductivity.

Dang, Y. Y.; Bhuiyan, M.S.; Paranthaman, M. P.

2008-01-01

85

40 CFR 721.10250 - Zirconium lysine complex (generic).  

Code of Federal Regulations, 2013 CFR

...2013-07-01 2013-07-01 false Zirconium lysine complex (generic). 721.10250 ...Substances § 721.10250 Zirconium lysine complex (generic). (a) Chemical...substance identified generically as zirconium lysine complex (PMN P-09-356) is...

2013-07-01

86

Processing fissile material mixtures containing zirconium and/or carbon  

DOEpatents

A method of processing spent TRIZO-coated nuclear fuel may include adding fluoride to complex zirconium present in a dissolved TRIZO-coated fuel. Complexing the zirconium with fluoride may reduce or eliminate the potential for zirconium to interfere with the extraction of uranium and/or transuranics from fission materials in the spent nuclear fuel.

Johnson, Michael Ernest; Maloney, Martin David

2013-07-02

87

Zirconium: biomedical and nephrological applications.  

PubMed

Recent years have witnessed a rapid increase in the use of zirconium (Zr)-containing compounds in artificial internal organs. Examples include dental implants and other restorative practices, total knee and hip replacement, and middle-ear ossicular chain reconstruction. In nephrological practice, Zr-containing sorbents have been used in hemofiltration, hemodialysis, peritoneal dialysis, and in the design and construction of wearable artificial kidneys. Zr compounds continue to be widely and extensively used in deodorant and antiperspirant preparations. In the public health arena, Zr compounds have been studied or used in controlling phosphorus pollution and in the reclamation of poison and bacteria-contaminated water. Experimental and clinical studies support the general consensus that Zr compounds are biocompatible and exhibit low toxicity. Reports on possible Zr-associated adverse reactions are rare and, in general, have not rigorously established a cause-and-effect relationship. Although publications on the use of Zr compounds have continued to increase in recent years, reports on Zr toxicity have virtually disappeared from the medical literature. Nevertheless, familiarity with, and continued vigilant monitoring of, the use of these compounds are warranted. This article provides an updated review on the biomedical use of Zr compounds. PMID:21245802

Lee, David B N; Roberts, Martin; Bluchel, Christian G; Odell, Ross A

2010-01-01

88

Review of zirconium-zircaloy pyrophoricity  

SciTech Connect

Massive zirconium metal scrap can be handled, shipped, and stored with no evidence of combustion or pyrophoricity hazards. Mechanically produced fine scrap such as shavings, turnings, or powders can burn but are not pyrophoric unless the particle diameter is less than 54 ..mu..m. Powders with particle diameters less than 54 ..mu..m can be both pyrophoric and explosive. Pyrophoric powders should be collected and stored underwater or under inert gas cover to reduce the flammability hazard. Opening sealed containers of zirconium stored underwater should be attempted with caution since hydrogen may be present. The factors that influence the ignition temperature have been explored in depth and recommendations are included for the safe handling, shipping, and storage of pyrophoric or flammable zirconium. 29 refs., 5 figs., 6 tabs.

Cooper, T.D.

1984-11-01

89

Nitrate uptake and nitrate reduction in synchronous Chlorella  

Microsoft Academic Search

Nitrate uptake was followed continuously in cultures of Chlorella sorokiniana using ionsensitive electrodes. During the lifecycle of the synchronous cell cultures, a drastic increase occurred in the first hour after the onset of the light. Nitrate uptake rate was shown to be dependent on illumination intensity, nitrate concentration, and temperature. These results point to an energy-linked uptake process. From the

Rudolf Tischner; Harald Lorenzen

1979-01-01

90

Radiation effects on corrosion of zirconium alloys  

SciTech Connect

From the wide use of zirconium alloys as components in nuclear reactors, has come clear evidence that reactor radiation is a major corrosion parameter. The evidence emerges from comparisons of zirconium alloy corrosion behavior in different reactor types, for example, BWRs versus PWRs and in corresponding reactor loop chemistries; also, oxidation rates differ with location along components such as fuel rods and reactor pressure tubes. In most respects, oxidation effects on power reactor components are paralleled by oxidation behavior on specimens exposed to radiation in reactor loops.

Johnson, A.B. Jr.

1989-06-01

91

Nitrate in groundwater  

Microsoft Academic Search

An intensive intrusion of nitrate into many aquifers has occurred in the last 20 years. Measures are discussed to prevent high concentrations of this pollutant in pumping wells. In the long run a less intensive use of mineral fertilizers and a diminished disposal of livestock wastes in the catchment areas of pumping wells are the presuppositions for an acceptable concentration

WOLFGANG MEIER; ROLF MULL

1989-01-01

92

Nitrate transport and signalling  

Microsoft Academic Search

Physiological measurements of nitrate (NO2 3 ) uptake by roots have defined two systems of high and low affinity uptake. In Arabidopsis, genes encoding both of these two uptake systems have been identified. Most is known about the high affinity transport system (HATS) and its regulation and yet measurements of soil NO2 3 show that it is more often available

Anthony J. Miller; Xiaorong Fan; Mathilde Orsel; Susan J. Smith; Darren M. Wells

2007-01-01

93

Structural and electrical properties of zirconium doped yttrium oxide nanostructures  

NASA Astrophysics Data System (ADS)

A synthetic process for the formation of ZrxY1-xOy nanostructures is demonstrated by the reaction of yttrium nitrate hexahydrate with zirconium propoxide. The reactions are carried out at temperature 60°C and pressure 0.1 MPa. The energy dispersive X-ray (EDX) spectroscopy measurements confirm formation of ZrxY1-xOy nanostructures and the presence of carbonate and hydroxide species which are removed after high temperature anneals. It was found that the oxygen pressure during synthesis plays a determinant role on the structural properties of the nanostructure. This effect is further studied by atomic force microscopy (AFM) measurements and scanning electron microscope (SEM), which showed the formation of an isotopically organized structure. X-ray diffraction (XRD) measurement reveals that these changes in the nanostructural efficiency are associated with structural and compositional changes among the substrate. The dielectric constant as measured by the capacitance-voltage (C-V) technique is estimated to be around 39.05. C-V measurements taken at 1 MHz show the maximum capacitance for the Zr0.05Y0.95Oy film. The leakage current densities were below 10-5 A/cm2 for the Zr0.05Y0.95Oy film.

Bahari, Ali; Ebrahimzadeh, Masoud; Gholipur, Reza

2014-04-01

94

Quantitative Infrared Spectrophotometry of Organic Nitrate Esters.  

National Technical Information Service (NTIS)

A quantitative infrared analysis of the N=O asymmetric stretching vibration band for the nitrate esters, ethyl nitrate, amyl nitrate, ethylene glycol dinitrate, glycerol trinitrate, and cellulose nitrate (12.53% N) is presented. Two solvents, chloroform a...

C. L. Hickman Y. P. Carignan

1972-01-01

95

Nitrate, bacteria and human health  

Microsoft Academic Search

Nitrate is generally considered a water pollutant and an undesirable fertilizer residue in the food chain. Research in the 1970s indicated that, by reducing nitrate to nitrite, commensal bacteria might be involved in the pathogenesis of gastric cancers and other malignancies, as nitrite can enhance the generation of carcinogenic N-nitrosamines. More recent studies indicate that the bacterial metabolism of nitrate

Eddie Weitzberg; Jeff A. Cole; Nigel Benjamin; Jon O. Lundberg

2004-01-01

96

The Economics of Nitrate Pollution  

Microsoft Academic Search

Nitrogen is essential to plant growth and, yet, excessive levels of nitrates in soil can cause problems of environmental pollution. In this paper, the author first considers the nitrogen cycles, tracing the movements of nitrogen to and from soils. The problems of excessive nitrate levels are then outlined, being effects on human health and eutrophication of water courses. Nitrate pollution

Nick Hanley

1990-01-01

97

Effect of zirconium carbide and carbon additions on some physicomechanical properties of zirconium diboride  

Microsoft Academic Search

ZrB2 and ZrC powders of approximately the same fineness (specific surface S = 0.12-0.16 m2\\/g) and a much finer PGI graphite powder (S = 12 m2\\/g) were employed. The compositions of the zirconium carbide and zirconium boride were close to stoichiometric; the oxygen and nitrogen contents of the compounds did not exceed a few tenths of one percent. As in

R. A. Andrievskii; L. A. Korolev; V. V. Klimenko; A. G. Lanin; I. I. Spivak; I. L. Taubin

1980-01-01

98

Low Dose Irradiation Growth in Zirconium.  

National Technical Information Service (NTIS)

Low dose neutron irradiation growth in textured and recrystallized zirconium, is studied, at the Candu Reactors Calandria temperature (340 K) and at 77 K. It was necessary to design and build 1: A facility to irradiate at high temperatures, which was inst...

A. M. Fortis

1987-01-01

99

Mass Spectrometric Study of Zirconium Diboride.  

National Technical Information Service (NTIS)

A mass spectrometer was used with a high temperature Knudsen effusion source to obtain vapor pressure data for zirconium diboride in the temperature range 2267 to 2445K. The heat of vaporization at 298K determined from a Third Law analysis of the data is ...

O. C. Trulson H. W. Goldstein

1964-01-01

100

Grain growth in zirconium diboride during sintering  

Microsoft Academic Search

The results are presented of an investigation into the growth of zirconium diboride grains during sintering. It is assumed that, during the initial period of sintering, grain growth is effected by a mechanism of grain displacement under the influence of surface tension forces, when grain matching occurs on polygonized boundaries. At sintering time of more than 30 min, grain growth

M. A. Kuzenkova; P. S. Kislyi

1966-01-01

101

Aluminum alloys containing scandium with zirconium additions  

US Patent & Trademark Office Database

Applications for aluminum alloys containing scandium with or without zirconium additions. Such modified aluminum alloys possess enhanced properties and exhibit improved processing characteristics, and, as such, are especially suited for use in recreational and athletic structures and components, and in certain aerospace, ground transportation and marine structures and components.

1997-04-15

102

Zirconium modified nickel-copper alloy  

NASA Technical Reports Server (NTRS)

An improved material for use in a catalytic reactor which reduces nitrogen oxide from internal combustion engines is in the form of a zirconium-modified, precipitation-strengthened nickel-copper alloy. This material has a nominal composition of Ni-30 Cu-0.2 Zr and is characterized by improved high temperature mechanical properties.

Whittenberger, J. D. (inventor)

1977-01-01

103

Zirconium alloy heat treatment process and product  

SciTech Connect

Zirconium-base alloy channels and fuel cladding tubes having unique resistance to accelerated pustular corrosion in the boiling water reactor environment are produced by a heat treatment causing segregation of intermetallic particulate precipitate phase in two dimensional arrays preferably located along grain boundaries and subgrain boundaries throughout the alloy body.

Black, T.J.; Proebstle, R.A.; Urquhart, A.W.; Walker, J.L.; Williams, C.D.

1980-12-09

104

Minerals Yearbook, 1988: Zirconium and Hafnium.  

National Technical Information Service (NTIS)

Domestic mine production of zircon, the principal ore mineral of zirconium and hafnium, increased in 1988. Zircon was mined by two companies in Florida as a coproduct of the titanium minerals ilmenite and rutile and by one company in New Jersey from taili...

J. B. Hedrick

1988-01-01

105

Zirconium and hafnium in meteorites  

NASA Astrophysics Data System (ADS)

The ratio of the two refractory trace elements zirconium (Zr) and hafnium (Hf) in meteorites has been proposed to be uniform. The most precise value available is 34.3+/-0.2 (1?). It was obtained by isotope dilution ICP-MS applied to 15 chondrites, most of which were carbonaceous chondrites, and six achondrites. We reinvestigated the case and determined Zr/Hf ratios of a broad spectrum of meteoritic samples via laser ablation ICP-MS. Our sample suite comprised 29 chondrites and five achondrites. The main objective of the study was two-fold: we intended to verify the accuracy and precision of a relatively fast and inexpensive sample preparation method combined with expeditious laser ablation ICP-MS techniques. Furthermore, we were looking into the possibility of systematic fine-scale Zr/Hf variations among bulk meteoritic matter of different classes. The applied fusion technique together with laser ablation ICP-MS turned out to be well suited to determine relative refractory trace element abundances. Absolute Zr/Hf ratios yield uncertainties of approximately 4% (1?). As opposed to the most recent findings, we observed variable Zr/Hf ratios in different meteorites ranging from approximately 28 to approximately 38. Our value for Orgueil (CI1) is 34.0+/-0.3 (1?). Including literature data, we propose a solar system value of 34.1+/-0.3. Our data also suggest that H chondrites tend to exhibit higher Zr/Hf ratios (average of 35.6+/-0.5 [1?]) while EL6 chondrites rather show low values (average of 30.8+/-0.6 [1?]). In addition to examining Zr/Hf ratios, we also explored the content of refractory major elements in different meteorite groups. Here, we found that EL6 chondrites often show very low Ca/Al ratios. The CI1 value for CaO/Al2O3 is 0.804. EL6 chondrites, however, display ratios as low as approximately 0.3. While the variation in Zr/Hf can be explained by fractional condensation processes in the early solar nebula, the observed low Ca/Al ratios in EL6 chondrites are probably attributable to deficits in oldhamite (CaS).

Patzer, Andrea; Pack, Andreas; Gerdes, Axel

2010-07-01

106

Purification of alkali metal nitrates  

DOEpatents

A process is disclosed for removing heavy metal contaminants from impure alkali metal nitrates containing them. The process comprises mixing the impure nitrates with sufficient water to form a concentrated aqueous solution of the impure nitrates, adjusting the pH of the resulting solution to within the range of between about 2 and about 7, adding sufficient reducing agent to react with heavy metal contaminants within said solution, adjusting the pH of the solution containing reducing agent to effect precipitation of heavy metal impurities and separating the solid impurities from the resulting purified aqueous solution of alkali metal nitrates. The resulting purified solution of alkali metal nitrates may be heated to evaporate water therefrom to produce purified molten alkali metal nitrate suitable for use as a heat transfer medium. If desired, the purified molten form may be granulated and cooled to form discrete solid particles of alkali metal nitrates.

Fiorucci, Louis C. (Hamden, CT); Gregory, Kevin M. (Woodridge, IL)

1985-05-14

107

Ammonium nitrate explosive systems  

DOEpatents

Novel explosives which comprise mixtures of ammonium nitrate and an ammonium salt of a nitroazole in desired ratios are disclosed. A preferred nitroazole is 3,5-dinitro-1,2,4-triazole. The explosive and physical properties of these explosives may readily be varied by the addition of other explosives and oxidizers. Certain of these mixtures have been found to act as ideal explosives.

Stinecipher, Mary M. (Los Alamos, NM); Coburn, Michael D. (Los Alamos, NM)

1981-01-01

108

Investigation of the Oxidation Resistance of Zirconium Boride-Molybdenum Disilicide Alloys.  

National Technical Information Service (NTIS)

This work examines the oxidation resistance of pure zirconium boride and zirconium boride-molybdenum disilicide alloys. It was found that the oxidation resistance of the zirconium boride-molybdenum disilicide alloys considerably exceeds that of pure zirco...

M. A. Kuzenkova P. S. Kislyi

1966-01-01

109

COMPARISON OF MUTAGENIC ACTIVITIES OF SEVERAL PEROXYACYL NITRATES  

EPA Science Inventory

Salmonella typhimurium strain TA100 was exposed to a series of peroxyacyl nitrates including peroxyacetyl nitrate (PAN), peroxypropionyl nitrate peroxybutyryl nitrate (PBN), peroxybenzoyl nitrate (PBzN), and chlororoxyacetyl nitrate (CPAN). as phase concentrations for the individ...

110

COMPARISON OF MUTAGENIC ACTIVITIES OF SEVERAL PEROXYACL NITRATES  

EPA Science Inventory

Salmonella typhimurium, strain TA100 was exposed to a series of peroxyacyl nitrates including peroxyacetyl nitrate (PAN), peroxypropionyl nitrate (PPN), peroxybutyryl nitrate (PBN), peroxybenzoyl nitrate (PBzN), and chloroperoxyacetyl nitrate (CPAN). as-phase concentrations for t...

111

Manufacturing process to reduce large grain growth in zirconium alloys  

DOEpatents

It is an object of the present invention to provide a procedure for desensitizing zirconium-based alloys to large grain growth (LGG) during thermal treatment above the recrystallization temperature of the alloy. It is a further object of the present invention to provide a method for treating zirconium-based alloys which have been cold-worked in the range of 2 to 8% strain to reduce large grain growth. It is another object of the present invention to provide a method for fabricating a zirconium alloy clad nuclear fuel element wherein the zirconium clad is resistant to large grain growth.

Rosecrans, P.M.

1984-08-01

112

Plastic deformation mechanisms of {beta} treated zirconium  

SciTech Connect

This study aims to determine the different deformation mechanisms of grade 702 zirconium under uniaxial tension and at room temperature. The grade 702 zirconium tested had undergone an {alpha} {yields} {beta} {yields} {alpha} cycle at a slow cooling rate ({approximately} 15{degree} s{sup {minus}1}). Three deformation mechanisms were identified: prismatic slip, (10{bar 1}2) <10{bar 1}{bar 1}> twinning and (11{bar 2}1) <11{bar 2}{bar 6}> twinning. The critical resolved shear stress for prismatic slip, (10{bar 1}2) <10{bar 1}{bar 1}> twinning and (11{bar 2}1) <11{bar 2}{bar 6}> twinning was also determined. The effect of the non-uniform redistribution of the hardening elements on location through the grain of the various mechanisms and on the tendency for localized deformation to develop is also discussed.

Crepin, J.; Bretheau, T.; Caldemaison, D. [Ecole Polytechnique, Palaiseau (France). Lab. de Mecanique des Solides] [Ecole Polytechnique, Palaiseau (France). Lab. de Mecanique des Solides

1995-10-01

113

Intercalation chemistry of zirconium 4-sulfophenylphosphonate  

NASA Astrophysics Data System (ADS)

Zirconium 4-sulfophenylphosphonate is a layered material which can be employed as a host for the intercalation reactions with basic molecules. A wide range of organic compounds were chosen to represent intercalation ability of zirconium 4-sulfophenylphosphonate. These were a series of alkylamines from methylamine to dodecylamine, 1,4-phenylenediamine, p-toluidine, 1,8-diaminonaphthalene, 1-aminopyrene, imidazole, pyridine, 4,4?-bipyridine, poly(ethylene imine), and a series of amino acids from glycine to 6-aminocaproic acid. The prepared compounds were characterized by powder X-ray diffraction, thermogravimetry analysis and IR spectroscopy and probable arrangement of the guest molecules in the interlayer space of the host is proposed based on the interlayer distance of the prepared intercalates and amount of the intercalated guest molecules.

Svoboda, Jan; Zima, Vít?zslav; Melánová, Klára; Beneš, Ludvík; Trchová, Miroslava

2013-12-01

114

Electronic structure of insulating zirconium nitride  

Microsoft Academic Search

The electronic structure of Zr3N4, grown by low-energy (0.25 keV) N+2 implantation of polycrystalline zirconium has been investigated by x-ray photoelectron spectroscopy. Both the valence-band and core-level spectra demonstrate the insulating characteristics of Zr3N4 as well as the metal-insulator phase transition in ZrNx when x~=1.33.

P. Prieto; L. Galán; J. M. Sanz

1993-01-01

115

Zirconium alloys in nuclear power engineering  

Microsoft Academic Search

Results of studies of zirconium alloys É110 and É635 that have served in parts of VVÉR-1000 reactors are presented. The influence of the composition on the properties of alloys É110 and É635 is studied and improved modifications are suggested. The effect of the total content of admixtures in alloy É110 on corrosion and embrittlement of pipes under conditions simulating LOCA

A. V. Nikulina

2004-01-01

116

Oxide layers with titanium and zirconium phosphates  

Microsoft Academic Search

Oxide-phosphate layers 20 to 150 ?m thick were obtained on titanium by plasma electrolytic deposition in individual and mixed\\u000a aqueous electrolytes with polyphosphate complexes of zirconium(IV), barium(II), and copper(II). Formation features, thickness,\\u000a elemental and phase compositions, and surface morphology of the films are presented. Depending on the electrolyte composition,\\u000a synthesis conditions, and temperature of annealing in air, some simple and

V. S. Rudnev; T. P. Yarovaya; P. M. Nedozorov; T. A. Kaidalova

2008-01-01

117

Thermal sprayed zirconium coatings for corrosion resistance  

SciTech Connect

Vacuum Plasma Spraying (VPS) is conducted in inert reduced pressures. This results in higher particle velocities than in atmospheric plasma spraying. Reverse arc sputter cleaning and pre-heating of the workpiece lead to elevated substrate temperatures during deposition, allowing sintering of the coating and, thus, enhanced densities and bond strengths. Inert Environment Electric Arc Spraying (IEAS) is performed in inert gas chambers, utilizing wire as the feedstock. This leads to lower gas content in the coating, since the initial gas content in wire is lower than that of the powder feedstock used in VPS. Controlled atmosphere sprayed zirconium coatings had inferior mechanical and corrosion properties when compared with bulk zirconium. The VPS coatings displayed higher bond strengths and better cavitation erosion resistance than did the IEAS coatings. The IEAS coatings had lower gas content and showed better electrochemical and corrosion behavior. The lower gas content for IEAS was due to a lower initial gas level in the wire feedstock used in this process. Also, scanning electron microscopy revealed that larger particles result in the IEAS process. Thus, a smaller surface-area-to-volume ratio is available for gas-metal reactions to occur. Improvements in mechanical and corrosion properties for the IEAS coatings were due to elevated substrate temperatures during deposition. Compressive surface stresses induced by post-spray shot-peening enhanced corrosion and cavitation resistance of IEAS coatings. Coating porosity caused failure during immersion testing. Therefore, it was concluded that controlled environment thermal spraying of zirconium is not suitable for forming corrosion resistant coatings on steel. ZrN coatings were formed by electric arc spraying using a nitrogen shroud and post-spray nitriding. Two phases; ZrN and zirconium solid solution, exist in the as-sprayed coating. Nitriding increases the proportion of ZrN.

Bamola, R.K.

1992-01-01

118

Thermodynamics of the gaseous zirconium iodides  

Microsoft Academic Search

The gaseous zirconium iodides ZrIâ, ZrIâ, ZrIâ, and ZrI, generated by the reaction of HI(g) with Zr(s) at elevated temperatures, were identified and characterized thermochemically by Knudsen cell mass spectrometry. Gaseous ZrIâ was the major reaction product up to about 1300°K; above this temperature, atomic I became the major product, with minor amounts of the lower Zr iodides appearing as

P. D. Kleinschmidt; D. Cubicciotti; D. L. hildenbrand

1978-01-01

119

Ion Exchange Reversibility of Some Radionuclides on Zirconium Tungstosuccinate and Zirconium Tungstosalicylate at their Solid-Liquid Interfaces  

Microsoft Academic Search

Zirconium tungstosuccinate (ZWSu) and zirconium tungstosalicylate (ZWSa) composites were synthesized by anchoring moieties of succinic acid (SuA) and salicylic acid (SaA) onto zirconium tungstate (ZW), respectively. The produced exchange composites were unambiguously characterized by TGA, DTA, XRD, and FTIR spectroscopy. Thermally stable, amorphous, highly active, and multifunctional inorganic-organic exchangers were produced. The sorption behavior of the hybrid materials for removal

B. El-Gammal; K. F. Allan

2012-01-01

120

Corrosion resistant zirconium alloy absorber material  

SciTech Connect

A method is described of making a zirconium alloy absorber material comprising the steps of: providing a zirconium alloy having iron in a range from about 0.2 to about 0.5 wt. %; about 50 to 120 ppm silicon; about 1,000 to 2,000 ppm oxygen; one or more additional alloying metals selected from the group consisting of tin in a range of from a measurable amount up to about 1.4 wt. chromium in a range from about 0.07 to about 0.25 wt. niobium in a range from a measurable amount up to about 0.6 wt. %, and vanadium in a range of from a measurable amount up to about 0.5 wt. %; and a balance of zirconium; and adding erbium in a range of from about 0.05 to 2.0 wt. % selected from the group consisting of a naturally occurring distribution of erbium isotopes, isotopically enriched erbium- 167, and a combination thereof to act as a burnable absorber.

Pati, S.R.; Corsetti, L.V.

1993-08-31

121

Neutronographic Texture Analysis of Zirconium Based Alloys  

NASA Astrophysics Data System (ADS)

Neutron diffraction is a very powerful tool in texture analysis of zirconium based alloys used in nuclear technique. Textures of five samples (two rolled sheets and three tubes) were investigated by using basal pole figures, inversion pole figures, and ODF distribution function. The texture measurement was performed at diffractometer KSN2 on the Laboratory of Neutron Diffraction, Department of Solid State Engineering, Faculty of Nuclear Sciences and Physical Engineering, CTU in Prague. Procedures for studying textures with thermal neutrons and procedures for obtaining texture parameters (direct and inverse pole figures, three dimensional orientation distribution function) are also described. Observed data were processed by software packages HEXAL and GSAS. Our results can be summarized as follows: i) All samples of zirconium alloys show the distribution of middle area into two maxima in basal pole figures. This is caused by alloying elements. A characteristic split of the basal pole maxima tilted from the normal direction toward the transverse direction can be observed for all samples, ii) Sheet samples prefer orientation of planes (100) and (110) perpendicular to rolling direction and orientation of planes (002) perpendicular to normal direction, iii) Basal planes of tubes are oriented parallel to tube axis, meanwhile (100) planes are oriented perpendicular to tube axis. Level of resulting texture and maxima position is different for tubes and for sheets. The obtained results are characteristic for zirconium based alloys.

Kruželová, M.; Vratislav, S.; Kalvoda, L.; Dlouhá, M.

2012-02-01

122

Study of the Hydroxylammonium Nitrate - Isopropyl Ammonium Nitrate Reaction.  

National Technical Information Service (NTIS)

When a balanced mixture of hydroxylammonium nitrate (HAN) and isopropyl ammonium nitrate (IPAN) in aqueous solution at appropriate concentrations is ignited in a high pressure bomb the reaction goes to completion to produce H2O, CO2 and N2. Some intermedi...

J. J. Kaufman W. S. Koski

1980-01-01

123

Evaluation of nitrate destruction methods  

SciTech Connect

A wide variety of high nitrate-concentration aqueous mixed [radioactive and Resource Conservation and Recovery Act (RCRA) hazardous] wastes are stored at various US Department of Energy (DOE) facilities. These wastes will ultimately be solidified for final disposal, although the waste acceptance criteria for the final waste form is still being determined. Because the nitrates in the wastes will normally increase the volume or reduce the integrity of all of the waste forms under consideration for final disposal, nitrate destruction before solidification of the waste will generally be beneficial. This report describes and evaluates various technologies that could be used to destroy the nitrates in the stored wastes. This work was funded by the Department of Energy`s Office of Technology Development, through the Chemical/Physical Technology Support Group of the Mixed Waste Integrated Program. All the nitrate destruction technologies will require further development work before a facility could be designed and built to treat the majority of the stored wastes. Several of the technologies have particularly attractive features: the nitrate to ammonia and ceramic (NAC) process produces an insoluble waste form with a significant volume reduction, electrochemical reduction destroys nitrates without any chemical addition, and the hydrothermal process can simultaneously treat nitrates and organics in both acidic and alkaline wastes. These three technologies have been tested using lab-scale equipment and surrogate solutions. At their current state of development, it is not possible to predict which process will be the most beneficial for a particular waste stream.

Taylor, P.A. [Oak Ridge National Lab., TN (United States); Kurath, D.E.; Guenther, R. [Pacific Northwest Lab., Richland, WA (United States)

1993-03-30

124

Catalyzed reduction of nitrate in aqueous solutions.  

National Technical Information Service (NTIS)

Sodium nitrate and other nitrate salts in wastes is a major source of difficulty for permanent disposal. Reduction of nitrate using aluminum metal has been demonstrated, but NH(sub 3), hydrazine, or organic compounds containing oxygen would be advantageou...

P. A. Haas

1994-01-01

125

76 FR 70366 - Ammonium Nitrate Security Program  

Federal Register 2010, 2011, 2012, 2013

...NPRM for the Ammonium Nitrate Security Program. The agenda for the public...Department's Ammonium Nitrate Security Program Web site, at http://www.dhs...programs/ammonium-nitrate-security-program.shtm. This...

2011-11-14

126

76 FR 62311 - Ammonium Nitrate Security Program  

Federal Register 2010, 2011, 2012, 2013

...NPRM) for the Ammonium Nitrate Security Program. The agenda for the public...Department's Ammonium Nitrate Security Program Web site in mid-October at http...programs/ammonium-nitrate-security-program.shtm. Each...

2011-10-07

127

[The nitrate content in milk].  

PubMed

Analytical possibilities for nitrate determination in milk on the base of photometric methods are discussed. An automated method, similar to Nijhuis u. a. (1979), is proposed using flow stream analyser ADM 300. Natrium nitrate (5 g and 10 g/kg live weight resp.) was given to two dairy cows after morning feeding on the 1st and on the 3rd day of experiment. The increase of nitrate content in the milk was very quick, maximal concentrations after 2 h were found as 5.6 mg/l (animal 1) and 3.2 mg nitrate-N/l (animal 2). But nitrate also disappeared relatively quickly, after 24 h there only values were observed corresponding to normal range of 1 mg/l. PMID:1953343

Geissler, C; Steinhöfel, O; Ulbrich, M

1991-08-01

128

Nitrate reductase from Rhodopseudomonas sphaeroides.  

PubMed Central

The facultative phototroph Rhodopseudomonas sphaeroides DSM158 was incapable of either assimilating or dissimilating nitrate, although the organism could reduce it enzymatically to nitrite either anaerobically in the light or aerobically in the dark. Reduction of nitrate was mediated by a nitrate reductase bound to chromatophores that could be easily solubilized and functioned with chemically reduced viologens or photochemically reduced flavins as electron donors. The enzyme was solubilized, and some of its kinetic and molecular parameters were determined. It seemed to be nonadaptive, ammonia did not repress its synthesis, and its activity underwent a rapid decline when the cells entered the stationary growth phase. Studies with inhibitors and with metal antagonists indicated that molybdenum and possibly iron participate in the enzymatic reduction of nitrate. The conjectural significance of this nitrate reductase in phototrophic bacteria is discussed.

Kerber, N L; Cardenas, J

1982-01-01

129

Formation of molybdenum and zirconium precipitates in concentrated uranyl nitrate solutions  

Microsoft Academic Search

The influence of the keeping time, temperature, and concentrations of U and HNO3 on the residual content of Mo and Zr in the solution was examined. An increase in the preliminary keeping time favors more\\u000a complete precipitation. An increase in the uranium concentration to 800 g l?1 and\\/or in the temperature to 105°C leads to growing formation of precipitates of

I. V. Khonina; A. A. Lumpov; A. Yu. Shadrin; B. Ya. Zilberman; N. G. Kravchenko

2010-01-01

130

Electronic structure and charge density of zirconium diboride  

Microsoft Academic Search

Self-consistent calculations of the electronic band structure of zirconium diboride, ZrB2, have been performed. The total and individual band charge densities are analyzed in terms of their site (zirconium or boron) symmetry and plotted. The total charge density shows very little charge asymmetry about either site.

Alfred C. Switendick

1991-01-01

131

Effect of Neutron Irradiation on Fracture Behavior of Zirconium  

Microsoft Academic Search

Detailed fractographic and microstructural examinations were made on neutron irradiated and unirradiated zirconium specimens deformed to fracture at temperatures between liquid nitrogen (77 K) and room temperature (295 K), to study the effect of neutron irradiation on the fracture behavior of zirconium. The fracture surface and the micro-structure of the necked portion of the specimen were observed by scanning and

Takeo ONCHI; Hideo KAYANO; Yasuhiro HIGASHIGUCHI

1980-01-01

132

Electronic structure and charge density of zirconium diboride  

Microsoft Academic Search

Self-consistent calculations of the electronic band structure of zirconium diboride, ZrBâ, have been performed. The total and individual band charge densities are analysed in terms of their site (zirconium or boron) symmetry and plotted. The total charge density shows very little charge asymmetry about either site. 6 refs., 6 figs., 37 tabs.

Switendick

1990-01-01

133

Electronic structure and charge density of zirconium diboride  

SciTech Connect

Self-consistent calculations of the electronic band structure of zirconium diboride, ZrB{sub 2}, have been performed. The total and individual band charge densities are analysed in terms of their site (zirconium or boron) symmetry and plotted. The total charge density shows very little charge asymmetry about either site. 6 refs., 6 figs., 37 tabs.

Switendick, A.C.

1990-01-01

134

Electronic structure and charge density of zirconium diboride  

NASA Astrophysics Data System (ADS)

Self-consistent calculations of the electronic band structure of zirconium diboride, ZrB2, have been performed. The total and individual band charge densities are analyzed in terms of their site (zirconium or boron) symmetry and plotted. The total charge density shows very little charge asymmetry about either site.

Switendick, Alfred C.

1991-07-01

135

Electronic structure and charge density of zirconium diboride  

SciTech Connect

Self-consistent calculations of the electronic band structure of zirconium diboride, ZrB{sub 2}, have been performed. The total and individual band charge densities are analyzed in terms of their site (zirconium or boron) symmetry and plotted. The total charge density shows very little charge asymmetry about either site.

Switendick, A.C. (Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States))

1991-07-01

136

Corrosion resistance of zirconium in chemical processing equipment  

SciTech Connect

The author describes some corrosion properties that make unalloyed zirconium a candidate material for the chemical process industry. Zirconium is compared with competitive materials of construction; corrosion problems and testing are described; aspects of fabrication are discussed. The paper concludes with a description of applications in the Du Pont Company.

Moniz, B.J.

1982-09-01

137

Frottement Lubrifie de la Zircone (Lubricated Friction of Zirconium).  

National Technical Information Service (NTIS)

The friction and wear behavior of zirconium in the presence of different lubricating agents was studied, and the wear mechanisms analyzed. A model of the wear evolution is developed. The friction/wear meter was of a sphere-plane type where the zirconium w...

P. Maurin-Perrier

1987-01-01

138

Process of precipitating zirconium or hafnium from spent pickling solutions  

Microsoft Academic Search

This patent describes a process for regenerating a spent, fluoride-containing pickle solution used in the pickling of zirconium or hafnium metal or their alloys. It comprises adding to the spent pickle solution a sufficient amount of sodium sulfate to precipitate sodium zirconium or hafnium fluoride.

C. L. Aguilar; R. G. Walker

1991-01-01

139

Separation of fluorine from zirconium and hafnium hydroxofluorides  

Microsoft Academic Search

Translated from Zh. Prikl. Khim.; 46: No. 7, 1438-1443(Jul For ; separation of fluorine by electrodialysis it is recommended that membranes which ; are inent with respect to zirconium fluoride complexes be used. Intensive ; separation of fluorine from zirconium (or hafnium) hydroxofluoride can be ; achieved by high-voltage electrodialysis at voltages above 600 V. The existence ; of previously

M. M. Godneva; D. L. Motov

1973-01-01

140

Process of precipitating zirconium or hafnium from spent pickling solutions  

SciTech Connect

This patent describes a process for regenerating a spent, fluoride-containing pickle solution used in the pickling of zirconium or hafnium metal or their alloys. It comprises adding to the spent pickle solution a sufficient amount of sodium sulfate to precipitate sodium zirconium or hafnium fluoride.

Aguilar, C.L.; Walker, R.G.

1991-12-31

141

Zirconium fluoride glass - Surface crystals formed by reaction with water  

NASA Technical Reports Server (NTRS)

The hydrated surfaces of a zirconium barium fluoride glass, which has potential for application in optical fibers and other optical elements, were observed by scanning electron microscopy. Crystalline zirconium fluoride was identified by analysis of X-ray diffraction patterns of the surface crystals and found to be the main constituent of the surface material. It was also found that hydrated zirconium fluorides form only in highly acidic fluoride solutions. It is possible that the zirconium fluoride crystals form directly on the glass surface as a result of its depletion of other ions. The solubility of zirconium fluoride is suggested to be probably much lower than that of barium fluoride (0.16 g/100 cu cm at 18 C). Dissolution was determined to be the predominant process in the initial stages of the reaction of the glass with water. Penetration of water into the glass has little effect.

Doremus, R. H.; Bansal, N. P.; Bradner, T.; Murphy, D.

1984-01-01

142

Swift heavy ion irradiation of zirconium phosphate of various forms  

NASA Astrophysics Data System (ADS)

The zirconium phosphate and its various derivatives have good resistance against ionization radiation, as it was found earlier during the irradiation of them with ?-rays of high energy. Continuing these experiments amorphous and crystalline (both ?- and ?-forms) zirconium phosphate, its monosodium, and propylamine intercalated forms were irradiated with a fluence of 10 11-10 14 ion cm -2 with swift heavy ions of 203Bi and 84Kr. The irradiation was also performed with Si containing zirconium phosphate. The structure of the materials was characterized by XRD method. The comparison of the powder diffraction patterns reveals that the irradiation has practically no effect on the ?-zirconium phosphate, while the other materials more or less destroyed and some of them became amorphous. The propylamine intercalate form of zirconium phosphate is decomposed on ?-ZrP and organic radical.

Szirtes, L.; Megyeri, J.; Kuzmann, E.; Havancsák, K.

2003-06-01

143

Nitrate concentrations under irrigated agriculture  

USGS Publications Warehouse

In recent years, considerable interest has been expressed in the nitrate content of water supplies. The most notable toxic effect of nitrate is infant methemoglobinemia. The risk of this disease increases significantly at nitrate-nitrogen levels exceeding 10 mg/l. For this reason, this concentration has been established as a limit for drinking water in many countries. In natural waters, nitrate is a minor ionic constituent and seldom accounts for more than a few percent of the total anions. However, nitrate in a significant concentration may occur in the vicinity of some point sources such as septic tanks, manure pits, and waste-disposal sites. Non-point sources contributing to groundwater pollution are numerous and a majority of them are related to agricultural activities. The largest single anthropogenic input of nitrate into the groundwater is fertilizer. Even though it has not been proven that nitrogen fertilizers are responsible for much of nitrate pollution, they are generally recognized as the main threat to groundwater quality, especially when inefficiently applied to irrigated fields on sandy soils. The biggest challenge facing today's agriculture is to maintain the balance between the enhancement of crop productivity and the risk of groundwater pollution. ?? 1982 Springer-Verlag New York Inc.

Zaporozec, A.

1983-01-01

144

Irradiation growth in zirconium and its alloys  

NASA Astrophysics Data System (ADS)

The UKAEA Northern Research Laboratories (Risley) have recently completed an underlying research study on irradiation growth in zirconium and its alloys. During this study, irradiation growth measurements have been made on a range of well-characterized single-crystal and polycrystalline iodide zirconium, commercial alloys Zircaloy-2 and Zr-2.5 wt% Nb, and high-purity zirconium-tin alloys in different metallurgical conditions following irradiation in the DIDO reactor at AERE Harwell. Irradiations were performed in three rigs operating at irradiation temperatures between 353 and 673 K. An important feature of the experimental programme was the capability to perform repeat length measurements on individual growth specimens at intervals during their irradiation programme. This facility has allowed accurate monitoring of the growth phenomenon and changes in growth behaviour induced by the combined effects of irradiation temperature and accumulated fast neutron dose over large dose ranges. This paper reviews the main experimental results from this programme and discusses them in terms of current understanding of the growth process. Thus, it has been observed that, in annealed Zircaloy-2 at temperatures between 553 and 673 K, a transition from saturating growth to accelerating growth rates occurs with increasing dose. The dose above which this "growth breakaway" takes place is seen to be inversely dependent on irradiation temperature in mis temperature range. The well-documented difference in growth behaviour between annealed and cold-worked Zircaloy-2 observed at relatively low irradiation temperatures, in which cold-worked material grows at a high linear rate over large dose ranges, is not observed at 673 K. Comparison is made with reported results on similar material irradiated in other irradiation facilities. The growth data are interpreted in terms of recent theories regarding the development during fast neutron irradiation of a cold-worked microstructure consisting of < a>- and < c>-type dislocations. Irradiation growth behaviour of annealed polycrystalline iodide zirconium between 353 and 673 K contrasts strongly with that in annealed Zircaloy-2 with low irradiation growth rates being observed over a large dose and temperature range. The influence of key irradiation parameters on the growth process have been examined in a series of studies initiated as part of a collaborative programme with AECL Chalk River Nuclear Labs. Final results from the studies on annealed and deformed single-crystal zirconium are reported here. They show that growth saturates rapidly at low dose in annealed single-crystal material irradiated at 353 and 553 K but that a gradual increase in growth strain is observed on irradiation to high dose at 553 K. Single-crystal specimens heavily swaged prior to irradiation at 353 K and given different pre-irradiation heat-treatments exhibit high near-linear or accelerating growth rates. These growth data are interpreted in terms of the importance of grain boundaries and twin boundaries as sinks for point defects which allow point defect separation and hence growth to continue to high dose. Finally, the results of growth experiments performed on Zr-0.1% Sn and Zr-1.5% Sn alloys at 353 and 553 K are reviewed. These experiments confirm the important role played by alloying additions and impurities on the growth process in zirconium and Zircaloy-2.

Rogerson, A.

1988-10-01

145

The irradiation effects on zirconium alloys  

NASA Astrophysics Data System (ADS)

Pressure tube samples were irradiated under helium atmosphere in the TRIGA Steady State Research and Material Test Reactor of the Romanian Institute for Nuclear Research (INR). These samples are made of the Zr-2.5%Nb alloy used as structural material for the CANDU Romanian power reactors. After irradiation, mechanical tests were performed in the Post Irradiation Examination Laboratory (PIEL) to study the influence of irradiation on zirconium alloys mechanical behaviour. The tensile test results were used for structural integrity assessment. Results of the tests are presented. The paper presents, also, pressure tube structural integrity assessment.

Negut, Gh.; Ancuta, M.; Radu, V.; Ionescu, S.; Stefan, V.; Uta, O.; Prisecaru, I.; Danila, N.

2007-05-01

146

Electron-momentum distribution in zirconium  

SciTech Connect

The electron-momentum distribution in hexagonal-close-packed zirconium has been studied for the first time with use of a Compton-scattering technique. Measurements have been made by scattering 59.54-keV ..gamma.. rays. Theoretical computations have been carried out with use of the renormalized-free-atom model for various 4d-5s configurations. Best agreement between theory and experiment is found if the electron configuration is chosen as 4d/sup 3/5s/sup 1/.

Sharma, B.K.; Ahuja, B.L.

1988-08-15

147

Density of Hydroxylammonium Nitrate Solutions.  

National Technical Information Service (NTIS)

Hydroxylammonium nitrate is miscible with water in all proportions at room temperature. The densities of such salt solutions were measured using water and deuterium oxide as solvents. A second order equation is given to relate to molar concentration. Keyw...

R. A. Sasse M. A. Davies R. A. Fifer M. M. Decker A. J. Kotlar

1988-01-01

148

Compartmental model of nitrate retention in streams  

Microsoft Academic Search

A compartmental modeling approach is presented to route nitrate retention along a cascade of stream reach sections. A process transfer function is used for transient storage equations with first-order reaction terms to represent nitrate uptake in the free stream and denitrification in the storage regions. In the context of a short-term nitrate injection we define nitrate assimilative capacity as 1

B. R. Faulkner; M. E. Campana

2007-01-01

149

Retrospective Reactor Dosimetry with Zirconium Alloy Samples  

SciTech Connect

Retrospective measurements are routinely performed with stainless steel samples. Recent experiments have been successfully conducted using zirconium alloy samples, involving somewhat different neuron activation reactions than are normally encountered with stainless steel samples. The alloy composition consisted of nominally 1% (by weight) niobium, 1% tin, and 0.1% iron, with the balance zirconium. The activation products observed in the samples by gamma spectroscopy included Zr-95, Nb-95, Sn-113, Sb-125, Mn-54, Co-60, Nb-94, and Ta-182. The niobium was then chemically separated following ASTM procedure E1297 and the Nb-93m activities were measured by x-ray spectroscopy. The thermal neutron fluences, as determined independently by the neutron capture gamma reactions to Zr-95, Sn-113, Nb-94, and Sn/Sb-125, were in excellent agreement. The fast neutron fluences, as determined separately by the Fe-54(n,p)Mn-54 and Nb-93(n,n’)Nb-93m reactions, were also in good agreement, thus demonstrating the versatility of the retrospective dosimetry technique.

Greenwood, Lawrence R.; Foster, John P.

2009-11-01

150

Nitrate assimilation in Lotus japonicus.  

PubMed

This paper summarizes some recent advances in the understanding of nitrate assimilation in the model legume Lotus japonicus. First, different types of experimental evidence are presented that emphasize the importance of the root in the nitrate-reducing assimilatory processes in this plant. Secondly, the main results from an ethyl methanesulphonate mutagenesis programme are presented. In this programme, chlorate-resistant and photorespiratory mutants were produced and characterized. The phenotype of one particular chlorate-resistant mutant suggested the importance of a low-affinity nitrate transport system for growth of L. japonicus plants under nitrate nutrition. The phenotype of photorespiratory mutants, affected in all forms of plastid glutamine synthetase in leaves, roots, and nodules, indicated that plastid glutamine synthetase was not required for primary nitrate assimilation nor for the symbiotic associations of the plant (nodulation, mycorrhization), provided photorespiration was suppressed. However, the phenotype of these mutants confirmed that plastid glutamine synthetase was required for the reassimilation of ammonium released by photorespiration. Finally, different aspects of the relationship between nitrate assimilation and osmotic stress in L. japonicus are also discussed, with specific reference to the biosynthesis of proline as an osmolyte. PMID:15911564

Márquez, Antonio J; Betti, Marco; García-Calderón, Margarita; Pal'ove-Balang, Peter; Díaz, Pedro; Monza, Jorge

2005-07-01

151

Kinetics of formation of a platelet-reinforced ceramic composite prepared by the directed reaction of zirconium with boron carbide  

Microsoft Academic Search

In this paper the kinetics of formation of a new class of ceramic composite material, zirconium diboride platelet-reinforced zirconium carbides, are discussed. These materials are prepared by the directed reaction of molten zirconium with boron carbide to form a ceramic material composed of zirconium diboride platelets approximately uniformly distributed in a zirconium carbide matrix containing a controlled amount of residual

William B. Johnson; Alan S. Nagelberg; Else Breval

1991-01-01

152

ANALYSIS OF URANIUM, THORIUM AND ZIRCONIUM  

Microsoft Academic Search

Considering the physico-chemical conditions for tributyl phosphate ; uranium extraction, the optimum nitrate concentration of the aqueous phase in ; which uranium separation by single extraction amounted virtually to 100% was ; determined. The extraction was carried out in tributyl phosphate--petrol ; solution and the uranium re-extracted in a dilute ammonium carbonate solution. ; The uranium content was determined by

Gy. Almassy; M. Ordogh; A. Schneer

1959-01-01

153

Atomic layer deposition of zirconium silicate films using zirconium tetrachloride and tetra-n-butyl orthosilicate  

Microsoft Academic Search

Atomic layer chemical vapor deposition of zirconium silicate films with a precursor combination of ZrCl4 and tetra-n-butyl orthosilicate (TBOS) was studied for high dielectric gate insulators. The effect of deposition conditions, such as deposition temperature, pulse time for purge and precursor injection on the deposition rate per cycle, and composition of the film were studied. At 400 °C, the growth

Won-Kyu Kim; Sang-Woo Kang; Shi-Woo Rhee; Nae-In Lee; Jong-Ho Lee; Ho-Kyu Kang

2002-01-01

154

Electronic structure of the cubic phase of zirconium dioxide  

Microsoft Academic Search

The band structure of the cubic phase of zirconium dioxide is obtained by employing the LMTO method. Its PV-diagram is calculated to determine the equilibrium lattice constant. The emission Zr LIII-spectrum of this compound is interpreted.

A. E. Krasovskii; A. S. Katashinskii; N. V. Parldaomenko

1994-01-01

155

Laves intermetallics in stainless steel-zirconium alloys.  

National Technical Information Service (NTIS)

Laves intermetallics have a significant effect on properties of metal waste forms being developed at Argonne National Laboratory. These waste forms are stainless steel-zirconium alloys that will contain radioactive metal isotopes isolated from spent nucle...

D. P. Abraham S. M. McDeavitt J. W. Richardson

1997-01-01

156

Reduction of nitrate in Shewanella  

SciTech Connect

In the genome of Shewanella oneidensis, a napDAGHB gene cluster encoding periplasmic nitrate reductase (NapA) and accessory proteins and an nrfA gene encoding periplasmic nitrite reductase (NrfA) have been identified. These two systems seem to be atypical because the genome lacks genes encoding cytoplasmic membrane electron transport proteins, NapC for NAP and NrfBCD/NrfH for NRF, respectively. Here, we present evidence that reduction of nitrate to ammonium in S. oneidensis is carried out by these atypical systems in a two-step manner. Transcriptional and mutational analyses suggest that CymA, a cytoplasmic membrane electron transport protein, is likely to be the functional replacement of both NapC and NrfH in S. oneidensis. Surprisingly, a strain devoid of napB encoding the small subunit of nitrate reductase exhibited the maximum cell density sooner than the wild type. Further characterization of this strain showed that nitrite was not detected as a free intermediate in its culture and NapB provides a fitness gain for S. oneidensis to compete for nitrate in the environments. On the basis results from mutational analyses of napA, napB, nrfA and napBnrfA in-frame deletion mutants, we propose that NapB is able to favor nitrate reduction by routing electrons to NapA exclusively.

Gao, Haichun [University of Oklahoma; Yang, Zamin Koo [ORNL; Barua, Sumitra [University of Oklahoma, Norman; Reed, SB [Pacific Northwest National Laboratory (PNNL); Nealson, Kenneth H. [University of Southern California; Fredrikson, JK [Pacific Northwest National Laboratory (PNNL); Tiedje, James [Michigan State University, East Lansing; Zhou, Jizhong [University of Oklahoma

2009-01-01

157

40 CFR 721.10152 - Oxirane, substituted silylmethyl-, hydrolysis products with alkanol zirconium(4+) salt and silica...  

Code of Federal Regulations, 2011 CFR

...products with alkanol zirconium(4+) salt and silica, acetates (generic). 721...products with alkanol zirconium(4+) salt and silica, acetates (generic). ...products with alkanol zirconium(4+) salt and silica, acetates (PMN...

2011-07-01

158

Modelling precipitation in zirconium niobium alloys  

NASA Astrophysics Data System (ADS)

A model has been developed to predict precipitation of ?-Nb in zirconium-niobium alloys. The model considers two transformation mechanisms; in situ transformation of any retained ?-Zr and homogeneous nucleation of ?-Nb. The two mechanisms are allowed to operate concurrently and compete for the available solute. The model has been calibrated and tested using data in the literature and is able to reasonably reproduce these results without introducing non-physical fitting parameters. It has then been applied to predict the effects of prior ?-Zr fraction, oxygen content, and temperature on the precipitation kinetics of ?-Nb. These calculations predict that prior ?-Zr fraction has a strong effect on the kinetics of subsequent ?-Nb evolution and that oxygen content is also critical, with higher oxygen levels predicted to result in faster kinetics and shift in the peak transformation rate to higher temperatures.

Robson, J. D.

2008-07-01

159

Zirconium deformation behavior: insights from EBSD measurements.  

SciTech Connect

The deformation of crystal-bar zirconium was investigated as a function of strain and strain rate through electron back-scattered diffraction (EBSD) characterization. The resultant data provided spatially resolved information on microstructure and texture evolution, individual twin system activity, and subsequent strain partitioning between twinned volume and parent grains. A range of deformation conditions was represented through quasi-static compression, 4-point beam bend tests at room and cryogenic temperature, and Taylor cylinder impact experiments. Effects from the interplay between slip and twinning deformation modes on anisotropic plasticity are considered in order to address the apparent trend toward isotropy at high rates. The role of various length scales on deformation behavior will be considered, along with the implications of these length scales on the assumptions typically invoked for plasticity modeling.

Bingert, J. F. (John F.); Mason, T. A. (Thomas A.); Kaschner, G. C. (George C.); Maudlin, P. J. (Paul J.); Gray, G. T. (George T.), III

2001-01-01

160

On the dynamic tensile strength of Zirconium  

NASA Astrophysics Data System (ADS)

Despite its fundamental nature, the process of dynamic tensile failure (spall) is poorly understood. Spall initiation via cracks, voids, etc, before subsequent coalesce, is known to be highly microstructure-dependant. In particular, the availability of slip planes and other methods of plastic deformation controls the onset (or lack thereof) of spall. While studies have been undertaken into the spall response of BCC and FCC materials, less attention has paid to the spall response of highly anisotropic HCP materials. Here the dynamic behaviour of zirconium is investigated via plate-impact experiments, with the aim of building on an ongoing in-house body of work investigating these highly complex materials. In particular, in this paper the effect of impact stress on spall in a commercially sourced Zr rod is considered, with apparent strain-rate softening highlighted.

Appleby-Thomas, G. J.; Hameed, A.; Vignjevic, R.; Hazell, P. J.; Painter, J.; Cademartori, S.

2014-05-01

161

Electronic Structures of Zirconium Hydride and Hydrogen Solid Solution  

Microsoft Academic Search

Electronic structures of zirconium hydride and hydrogen solid solution have been evaluated by the X?ray photoelec- tron spectroscopy andrst-principles molecular orbital calculation. From the valence band spectra of the solid zirconium hydride, the occurrence of the valence electron transfer from Zr 4d band to Zr?H bonding state was found to induce the reduction of Zr?Zr metallic bonds with increasing the

Takanori NISHIZAKI; Shinsuke YAMANAKA

162

Nitridation of zirconium using energetic ions from plasma focus device  

Microsoft Academic Search

The nitridation of zirconium disks is achieved by irradiating energetic nitrogen ions from 2.3 kJ plasma focus device using multiple focus deposition shots (10, 20, 30 and 40) at different angular positions with respect to the anode axis. The X-ray diffraction analysis reveals the evolution of ZrN, Zr2N and Zr3N4 phases of zirconium nitride depending upon the ion energy flux and

I. A. Khan; M. Hassan; R. Ahmad; A. Qayyum; G. Murtaza; M. Zakaullah; R. S. Rawat

2008-01-01

163

Laves intermetallics in stainless steel-zirconium alloys  

Microsoft Academic Search

Laves intermetallics have a significant effect on properties of metal waste forms being developed at Argonne National Laboratory. These waste forms are stainless steel-zirconium alloys that will contain radioactive metal isotopes isolated from spent nuclear fuel by electrometallurgical treatment. The baseline waste form composition for stainless steel-clad fuels is stainless steel-15 wt.% zirconium (SS-15Zr). This article presents results of neutron

D. P. Abraham; S. M. McDeavitt; J. W. Jr. Richardson

1997-01-01

164

The freezing on of zirconium boride thermocouple sheaths  

Microsoft Academic Search

1.The freezing on method of preparation of zirconium boride sheaths is highly promising, and secures blank-shaping properties which are not exceeded by the properties of sheaths made by die extrusion.2.The best processing characteristics are shown by fine zirconium boride powder slips with 8–10% paraffin wax and 1% of oleic acid, from which it is possible to produce blanks with a

P. S. Kislyi; M. A. Kuzenkova

1965-01-01

165

Critical role of nitrogen during high temperature scaling of zirconium  

NASA Technical Reports Server (NTRS)

The mechanisms of scale cracking, scale color changes, and scale growth, and their interrelations, were studied in zirconium specimens at elevated temperatures in air, oxygen and nitrogen. Nitrogen was found to be responsible for monoclinic-to-cubic ZrO2 conversion, for scale cracking and breakaway on zirconium nitride, and for the formation of ZrN on the metal interface underneath an outer oxide layer.

Evans, E. B.; Tsangarakis, N.; Probst, H. B.; Garibotti, N. J.

1973-01-01

166

Quercetin as colorimetric reagent for determination of zirconium  

USGS Publications Warehouse

Methods described in the literature for the determination of zirconium are generally designed for relatively large amounts of this element. A good procedure using colorimetric reagent for the determination of trace amounts is desirable. Quercetin has been found to yield a sensitive color reaction with zirconium suitable for the determination of from 0.1 to 50?? of zirconium dioxide. The procedure developed involves the separation of zirconium from interfering elements by precipitation with p-dimethylaminoazophenylarsonic acid prior to its estimation with quercetin. The quercetin reaction is carried out in 0.5N hydrochloric acid solution. Under the operating conditions it is indicated that quercetin forms a 2 to 1 complex with zirconium; however, a 2 to 1 and a 1 to 1 complex can coexist under special conditions. Approximate values for the equilibrium constants of the complexes are K1 = 0.33 ?? 10-5 and K2 = 1.3 ?? 10-9. Seven Bureau of Standards samples of glass sands and refractories were analyzed with excellent results. The method described should find considerable application in the analysis of minerals and other materials for macro as well as micro amounts of zirconium.

Grimaldi, F. S.; White, C. E.

1953-01-01

167

Chromatographic separation of sodium, cobalt and europium on the particles of zirconium molybdate and zirconium silicate ion exchangers  

Microsoft Academic Search

Zirconium molybdate and zirconium silicate were prepared by application of the precipitation and sol–gel routes, respectively. The produced ion exchange powders were physically characterized using X-ray diffraction, infrared and differential thermal analysis. The obtained data revealed that they are thermally and chemically stable, having unique microstructure properties that permit their use in chromatographic separation of Na+, Co2+, and Eu3+ from

B. El-Gammal; S. A. Shady

2006-01-01

168

Acetonyltriphenyl-phospho-nium nitrate  

PubMed Central

Crystals of the title salt, C21H20OP+·NO3 ?, are composed of acetonyltriphenyl­phospho­nium cations and nitrate anions that mainly inter­act through electrostatic forces. The P atom in the cation has a slightly distorted tetra­hedral environment, with C—P—C angles ranging from 104.79?(7) to 112.59?(6)°. The sum of O—N—O angles of the nitrate anion is 359.99°, reflecting its trigonal–planar character. C—H?O hydrogen bonds help to consolidate the crystal packing.

Diop, Tidiane; Diop, Libasse; Kucerakova, Monika; Dusek, Michal

2013-01-01

169

Estimating peak nitrate concentrations from annual nitrate loads  

NASA Astrophysics Data System (ADS)

The feasibility of adopting an empirical approach to predicting peak nitrate concentrations in water draining agricultural land is examined in the light of the relationships derived from leaching experiments on a range of soils, and from river data for England and Wales for the period 1974-1986. Well-fitted linear regressions were obtained of peak nitrate concentration in leachate on the annual load of leachable nitrate in the soil. The slopes to the regressions ranged in value from greater than 1.3 for measurements in shallow soils over limestone in a low rainfall area, to 0.25 for a well-structured clay soil with mole drainage in a high rainfall area. (A slope of 1.0 means that a load of 100 kg N ha -1 gives rise to a peak concentration of 100 mg N 1 -1). This range mainly reflected the ranges in soil water capacity and degree of preferential flow occurring during drainage. The slopes to the regressions for river waters were consistently smaller than those for clay soils in the same areas. The slopes for rivers draining mainly low-lying clay or chalk catchments in drier areas (Thames, Anglian and Southern Water Authority areas) were generally greater than those for rivers draining mainly wetter and more upland areas (South West and Welsh Water Authority areas). The differences between the slopes to the regressions for rivers could be partly accounted for by differences in average rainfall, suggesting possible effects from systematic differences in land use, soil structure and date of rewetting of soils in different climatic areas. The regressions indicated that peak concentrations in excess of the European Community limit (11.3 mg 1 -1 nitrate-N) might be associated with total nitrate loads in rivers draining clay catchments of 30 kg N hat in central and eastern England, or greater than 70 kg N ha -1 in Wales. The results indicate that the regressions for soils might form the basis of a catchment-scale model of nitrate leaching, provided that it is linked with a hydrogeological sub-model that accounts for the contribution to river discharge from upland and groundwater sources, and for the effects of different land uses on the timing of the peak nitrate concentrations.

Scholefield, D.; Lord, E. I.; Rodda, H. J. E.; Webb, B.

1996-11-01

170

New Synthesis of Fluorine Nitrate.  

National Technical Information Service (NTIS)

The reaction of NF4(+)SbF6(-) with alkali metal nitrates in either CH3CN or SO2 solution at low temperature produces FONO2 in quantitative yield. Attempts were unsuccessful to prepare FONO from NF4SbF6 and KNO2 in an analogous manner.

B. Hoge K. O. Christe

2000-01-01

171

Toxicity Studies of Triaminoguanidine Nitrate.  

National Technical Information Service (NTIS)

The acute toxicity of triaminoguanidine nitrate (TAGN) has been studied. The LD(50) of TAGN in mice was 3.65 g/kg with 95% confidence limits of 3.54 - 3.76 g/kg. At IV doses of 50-200 mg/kg given to anesthetized dogs, TAGN caused a slightly decreased hear...

R. A. Davis C. T. Olson R. N. Terpolilli K. C. Back

1977-01-01

172

Nitrate accumulation in forage brassicas  

Microsoft Academic Search

Previous research has shown that the application of fertilizer nitrogen (N) can lead to an accumulation of nitrate nitrogen (NO3-N) in forage brassicas, particularly when N application rates exceed that required to obtain maximum crop yield. However, there are no data examining the effect of timing of fertilizer application on NO3-N accumulation. An experiment was established in 2009 with four

AL Fletcher; E Chakwizira

2012-01-01

173

Organic Nitrates from Isoprene during BEARPEX-2009  

NASA Astrophysics Data System (ADS)

Organic nitrates transport nitrogen oxides, and impact ozone formation. A subset of organic nitrates, hydroxy-nitrates from isoprene (sum of isomers), methyl vinyl ketone, and methacrolein, were measured using chemical ionization mass spectrometry during BEARPEX 2009. These measurements are used to assess the contribution of isoprene to the fraction of total alkyl nitrates observed over the ponderosa pine forest plantation. Implications for the mechanism of isoprene oxidation in the presence of nitrogen oxides are discussed.

Beaver, M. R.; St. Clair, J.; Paulot, F.; Spencer, K. M.; Crounse, J.; Min, K.; Pusede, S. E.; Lafranchi, B. W.; Browne, E. C.; Cohen, R. C.; Wennberg, P. O.

2010-12-01

174

A Novel Chemical Nitrate Destruction Process  

SciTech Connect

Nitrates represent one of the most significant pollutant discharged to the Baltic Sea by the Sliiamae hydrometallurgical plant. This article contains a brief overview of the existing nitrate destruction technologies followed by the description of a new process developed by the authors. The new chemical process for nitrate destruction is cost effective and simple to operate. It converts the nitrate to nitrogen gas which goes to the atmosphere.

Dziewinski, J.; Marczak, S.

1999-03-01

175

Zirconium and Niobium Extraction from HCl Media with di-N-Butyl Phosphorodithioic Acid.  

National Technical Information Service (NTIS)

The solvent extraction of zirconium and niobium di-n-butyl phosphoroditioate into organic diluents from HCl media is presented. The effect of extractant and mineral acid concentration on the zirconium and niobium distribution ratios as plots of lg. distri...

V. C. Iliescu

1978-01-01

176

Chemistry of Zirconium Related to the Behavior of Nuclear Fuel Cladding. Final Report.  

National Technical Information Service (NTIS)

Studies of the chemistry of the zirconium-iodine and zirconium-oxygen systems were undertaken to elucidate their thermodynamics and kinetics. It is anticipated that the results obtained will lead to an improved understanding of the chemical processes invo...

D. Cubicciotti

1980-01-01

177

Plasma nitrate and nitrite are increased by a high nitrate supplement, but not by high nitrate foods in older adults  

PubMed Central

Little is known about the effect of dietary nitrate on the nitrate/nitrite/NO (nitric oxide) cycle in older adults. We examined the effect of a 3-day control diet vs. high nitrate diet, with and without a high nitrate supplement (beetroot juice), on plasma nitrate and nitrite kinetics, and blood pressure using a randomized four period cross-over controlled design. We hypothesized that the high nitrate diet would show higher levels of plasma nitrate/nitrite and blood pressure compared to the control diet, which would be potentiated by the supplement. Participants were eight normotensive older men and women (5 female, 3 male, 72.5±4.7 yrs) with no overt disease or medications that affect NO metabolism. Plasma nitrate and nitrite levels and blood pressure were measured prior to and hourly for 3 hours after each meal. The mean daily changes in plasma nitrate and nitrite were significantly different from baseline for both control diet+supplement (p<0.001 and =0.017 for nitrate and nitrite, respectively) and high nitrate diet+supplement (p=0.001 and 0.002), but not for control diet (p=0.713 and 0.741) or high nitrate diet (p=0.852 and 0.500). Blood pressure decreased from the morning baseline measure to the three 2 hr post-meal follow-up time-points for all treatments, but there was no main effect for treatment. In healthy older adults, a high nitrate supplement consumed at breakfast elevated plasma nitrate and nitrite levels throughout the day. This observation may have practical utility for the timing of intake of a nitrate supplement with physical activity for older adults with vascular dysfunction.

Miller, Gary D.; Marsh, Anthony P.; Dove, Robin W.; Beavers, Daniel; Presley, Tennille; Helms, Christine; Bechtold, Erika; King, S. Bruce; Kim-Shapiro, Daniel

2012-01-01

178

Nitration of Naphthol: A Laboratory Experiment.  

ERIC Educational Resources Information Center

Products of nitrations, upon distillation or steam distillation, may produce dermatitis in some students. A procedure for nitration of beta-naphthol producing a relatively non-volatile product not purified by steam distillation is described. Nitration of alpha-naphthol by the same procedure yields Martius Yellow dye which dyes wool yellow or…

Mowery, Dwight F.

1982-01-01

179

21 CFR 172.160 - Potassium nitrate.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 2009-04-01 true Potassium nitrate. 172.160 Section 172.160 Food...CONSUMPTION Food Preservatives § 172.160 Potassium nitrate. The food additive potassium nitrate may be safely used as a curing agent...

2010-01-01

180

21 CFR 172.160 - Potassium nitrate.  

Code of Federal Regulations, 2013 CFR

...2013-04-01 2013-04-01 false Potassium nitrate. 172.160 Section 172.160 Food...CONSUMPTION Food Preservatives § 172.160 Potassium nitrate. The food additive potassium nitrate may be safely used as a curing agent...

2013-04-01

181

21 CFR 172.160 - Potassium nitrate.  

Code of Federal Regulations, 2010 CFR

...2009-04-01 2009-04-01 false Potassium nitrate. 172.160 Section 172.160 Food...CONSUMPTION Food Preservatives § 172.160 Potassium nitrate. The food additive potassium nitrate may be safely used as a curing agent...

2009-04-01

182

DO ORGANIC FARMING PRACTICES REDUCE NITRATE LEACHING?  

Microsoft Academic Search

Agriculture is a contributor of nitrate to natural waters and there is concern about the excess nitrogen burden loadings from agriculture on natural waters. Agricultural practices that reduce nitrate leaching from arable land are needed. It is postulated by certain groups that organic farming practices reduce nitrate leaching among other environmental benefits. The objectives of this paper are: (1) to

Holger Kirchmann; Lars Bergström

2001-01-01

183

The position of nitrate respiration in evolution.  

PubMed

Egami's hypothesis that oxygen respiration evolved from nitrate respiration, and this from nitrate fermentation, is not accepted. The reasons are: (1) Presumably there was no nitrate before O2 in the biosphere. (2) On mechanistic grounds, respiration (oxidative phosphorylation) is to be derived directly from photosynthesis (photosynthetic phosphorylation) rather than from any form of fermentation. PMID:917501

Broda, E

1977-08-01

184

Removal of nitrates from groundwater by electrocoagulation  

Microsoft Academic Search

In this study, coagulation and electrocoagulation processes were compared with regard to their respective efficiencies as to the removal of nitrates from water. The results indicate that electrocoagulation is an effective technology for nitrate removal because nitrate anions preferentially adsorb onto the surfaces of growing metal-hydroxide precipitates. Other similar results were observed when using iron or aluminium electrodes whenever coagulation

Engracia Lacasa; Pablo Cañizares; Cristina Sáez; Francisco J. Fernández; Manuel A. Rodrigo

2011-01-01

185

Interaction of ytterbium trifluoride with zirconium in a NaF-ZrF 4 molten mixture  

Microsoft Academic Search

The interaction of ytterbium trifluoride with zirconium in a molten mixture of sodium and zirconium fluorides have been studied\\u000a by differential thermal analysis, X-ray diffraction, and electronic and IR spectroscopy. In the temperature range 440–640°C,\\u000a zirconium reduces YbF3 to ytterbium. The reaction products also contain low-valence zirconium and ytterbium compounds.

N. M. Kompanichenko; R. N. Savchuk; N. V. Faidyuk; A. A. Omel’chuk; V. F. Zinchenko; N. I. Buryak

2008-01-01

186

Non-chromate corrosion inhibitor formulas based on zirconium vanadium oxide compositions  

US Patent & Trademark Office Database

A mixture of zirconium hydroxides or zirconium basic carbonate with vanadium oxide (V205) co-reacts in high temperature aqueous slurry to form respectively an amorphous material, believed to be based on a zirconium analog of a zeolite structure, and a solid solution of zirconium oxide with vanadium oxide. The subject compositions, free of hexavalent chromium, are highly effective in providing blister-free corrosion prevention in typical coil and aerospace grade epoxy primer and color coat combinations.

2012-03-20

187

LIQUID-LIQUID EXTRACTION OF HAFNIUM FROM ZIRCONIUM BY TRIBUTYL PHOSPHATE  

Microsoft Academic Search

ABS>The removal of hafnium from zirconium is one of a number of ; operations required to produce high purity zirconium metal for use in nuclear ; reactors. Since the metallurgical operations involved in the production of ; zirconium must use the products of hafnium-removal processes, the choice of a ; process for hafnium removal must be integrated with subsequent metallurgical

G. H. Beyer; H. C. Peterson

1951-01-01

188

METALLURGICAL PROBLEMS IN FABRICATION OF ZIRCONIUM-CLAD FUEL ELEMENTS FOR PRESSURIZED WATER REACTORS  

Microsoft Academic Search

To achieve adequate corrosion resistance in high-temperature water, the ; chemical composition and fabrication of zirconium cladding material must be ; carefully controlled. Present technology permits the satisfactory fabrication of ; a variety of fuel materials which are compatible with zirconium cladding. ; Homogeneity and melting cruci-ble problems still exist with some of the fuel ; alloys. Zirconium-clad fuel elements

1958-01-01

189

Synthesis of mesoporous zirconium titanates using alkycarboxylate surfactants and their transformation to dense ceramics  

Microsoft Academic Search

Mesoporous zirconium titanates with Ti\\/Zr ratios of two have been prepared through the controlled hydrolysis of mixtures of zirconium and titanium alkoxides and long chain carboxylates (lauric, palmitic or stearic acids) in the absence of solvent. X-ray diffraction, transmission electron microscopy, and gas adsorption measurements indicate that the zirconium titanate mesophases consist of a disordered arrangement of uniform pores. The

Vittorio Luca; Willem K. Bertram; Jonathan Widjaja; David R. G. Mitchell; Christopher S. Griffith; Elizabeth Drabarek

2007-01-01

190

Synthesis and characterization of a mesoporous hydrous zirconium oxide used for arsenic removal from drinking water  

Microsoft Academic Search

Powder (20–50?m) mesoporous hydrous zirconium oxide was prepared from a zirconium salt granular precursor. The effect of some process parameters on product morphology, porous structure and adsorption performance has been studied. The use of hydrous zirconium oxide for selective arsenic removal from drinking water is discussed.

Anatoly Bortun; Mila Bortun; James Pardini; Sergei A. Khainakov; José R. García

2010-01-01

191

Electrochemical studies of zirconium and hafnium in alkali chloride and alkali fluoride-chloride molten salts  

Microsoft Academic Search

The electrochemical reduction of zirconium and hafnium in alkali chloride or fluoride-chloride molten salts on platinum electrodes has been investigated by means of linear and cyclic voltammetry. It has been found that fluoride ions greatly influenced the reduction of zirconium and hafnium in fluoride-chloride melts. It has been proposed that the mechanism for reduction of zirconium and hafnium in baths

Chen Guang-Sen; Masazumi Okido; Takeo Oki

1990-01-01

192

A case study of the development of a military specification - zirconium powder for thermal batteries  

NASA Astrophysics Data System (ADS)

Thermal batteries are used as the critical power source in nuclear fuses, missiles, and aircraft. Heat sources in thermal batteries use a fine zirconium powder. This report focuses on the zirconium problem and the development of a military specification for zirconium powder as produced by the magnesium reduction method.

Burgess, Mary T.

1987-10-01

193

Preparation and Properties of Nitrate-Deficient Gadolinium Nitrate Solutions  

SciTech Connect

Because of the high neutron absorption cross sections of some gadolinium isotopes, gadolinium salts in solution are used to control nuclear reactivity in aqueous systems. The present studies concern the preparation and analysis of nitrate-deficient solutions, the effect of time and gamma radiation on their stability, and the determination of the solubility of gadolinium hydroxide in H2O and D2O.

Baumann, E.W.

2001-03-15

194

Equilibrium properties of hcp titanium and zirconium  

NASA Astrophysics Data System (ADS)

The electronic and structural properties of hexagonal-close-packed titanium and zirconium are determined from self-consistent linearized augmented-plane-wave (LAPW) calculations within the framework of the local-density-functional approximation (LDA). The equilibrium lattice parameters, bulk moduli, Poisson's ratios, and cohesive energies are obtained from the total energies calculated as functions of the a and c lattice parameters. As found in other LDA calculations, the cohesive energies are overestimated compared to experiment, but otherwise generally good agreement with experiment is obtained. The uncertainty in the results due to the particular choice of the LDA exchange-correlation potential is also examined by performing parallel calculations using the Kohn-Sham-Gaspar X? (?=(2/3) exchange-only potential. We find that these calculations yield equilibrium volumes which differ by 6-8 % (with the X? results in better agreement with experiment) with proportional differences in other structural properties, which we take to be an indication of the intrinsic reliability of the LDA.

Lu, Zhi-Wei; Singh, David; Krakauer, Henry

1987-11-01

195

Transport properties of zirconium alloy oxide films  

NASA Astrophysics Data System (ADS)

The conductivity mechanism of oxide films on tubes of various zirconium alloys grown in water and steam was investigated by I- V measurements. Electrodes of Ga, Ag, graphite and Au gave different results. The current decrease at voltage application was due to formation of space charge, which could be extracted again as short-circuit current. The positive branch of the I- V characteristics could be fitted by a second-order polynomial. Neither the Schottky emission mechanism nor the Poole-Frenkel effect could be proved. A high invariable carrier concentration with extremely low, but temperature dependent mobility could be proved using the Mott-Guerney relation. The carriers originate from oxygen vacancies in a substoichiometric black oxide layer near the metal-oxide interface. The conduction mechanism is believed to be a hopping process of electrons between oxygen-vacancy traps. There exists a small ionic conduction part, building up an open-circuit voltage so that the I- V characteristics do not pass through the origin. The Meyer-Neldel rule applies.

Frank, H.

2002-12-01

196

Nitrated fatty acids: Synthesis and measurement  

PubMed Central

Nitrated fatty acids are the product of nitrogen dioxide reaction with unsaturated fatty acids. The discovery of peroxynitrite and peroxidase-induced nitration of biomolecules led to the initial reports of endogenous nitrated fatty acids. These species increase during ischemia reperfusion, but concentrations are often at or near the limits of detection. Here, we describe multiple methods for nitrated fatty acid synthesis, sample extraction from complex biological matrices, and a rigorous method of qualitative and quantitative detection of nitrated fatty acids by LC-MS. In addition, optimized instrument conditions and caveats regarding data interpretation are discussed.

Woodcock, Steven R.; Bonacci, Gustavo; Gelhaus, Stacy L.; Schopfer, Francisco J.

2012-01-01

197

Tyrosine nitration in prostaglandin H(2) synthase.  

PubMed

In this study, we investigated the effects of various nitrogen oxide (NO(x)) species on the extent of prostaglandin H(2) synthase-1 (PGHS-1) nitration in purified protein and in vascular smooth muscle cells. We also examined PGHS-1 activity under these conditions and found the degree of nitration to correlate inversely with enzyme activity. In addition, since NO(x) species are thought to invoke damage during the pathogenesis of atherosclerosis, we examined human atheromatous tissue for PGHS-1 nitration. Both peroxynitrite and tetranitromethane induced Tyr nitration of purified PGHS-1, whereas 1-hydroxy-2-oxo-3-(N-methyl-aminopropyl)-3-methyl-1-triazene (NOC-7; a nitric oxide-releasing compound) did not. Smooth muscle cells treated with peroxynitrite showed PGHS-1 nitration. The extent of nitration by specific NO(x) species was determined by electrospray ionization mass spectrometry. Tetranitromethane was more effective than peroxynitrite, NOC-7, and nitrogen dioxide at nitrating a tyrosine-containing peptide (12%, 5%, 1%, and <1% nitration, respectively). Nitrogen dioxide and, to a lesser extent, peroxynitrite, induced dityrosine formation. Using UV/Vis spectroscopy, it was estimated that the reaction of PGHS-1 with excess peroxynitrite yielded two nitrated tyrosines/PGHS-1 subunit. Finally, atherosclerotic tissue obtained from endarterectomy patients was shown to contain nitrated PGHS-1. Thus, prolonged exposure to elevated levels of peroxynitrite may cause oxidative damage through tyrosine nitration. PMID:12364556

Deeb, Ruba S; Resnick, Matthew J; Mittar, Dev; McCaffrey, Timothy; Hajjar, David P; Upmacis, Rita K

2002-10-01

198

Deconstructing nitrate isotope dynamics in aquifers  

NASA Astrophysics Data System (ADS)

The natural abundance N and O stable isotope ratios of nitrate provide an invaluable tool to differentiate N sources to the environment, track their dispersal, and monitor their attenuation by biological transformations. The interpretation of patterns in isotope abundances relies on knowledge of the isotope ratios of the source end-members, as well as on constraints on the isotope discrimination imposed on nitrate by respective biological processes. Emergent observations from mono-culture experiments of denitrifying bacteria reveal nitrate fractionation trends that appear at odds with trends ascribed to denitrification in soils and aquifers. This discrepancy raises the possibility that additional biological N transformations may be acting in tandem with denitrification. Here, the N and O isotope enrichments associated with nitrate removal by denitrification in aquifers are posited to bear evidence of coincident biological nitrate production - from nitrification and/or from anammox. Simulations are presented from a simple time-dependent one-box model of a groundwater mass ageing that is subject to net nitrate loss by denitrification with coincident nitrate production by nitrification or anammox. Within boundary conditions characteristic of freshwater aquifers, the apparent slope of the parallel enrichments in nitrate N and O isotopes associated with net N loss to denitrification can vary in proportion to the nitrate added simultaneous by oxidative processes. Pertinent observations from nitrate plumes in suboxic to anoxic aquifers are examined to validate this premise. In this perspective, nitrate isotope distributions suggest that we may be missing important N fluxes inherent to most aquifers.

Granger, J.

2012-12-01

199

Phase diagram of ammonium nitrate  

NASA Astrophysics Data System (ADS)

Ammonium Nitrate (AN) has often subjected to uses in improvised explosive devices, due to its wide availability as a fertilizer and its capability of becoming explosive with slight additions of organic and inorganic compounds. Yet, the origin of enhanced energetic properties of impure AN (or AN mixtures) is neither chemically unique nor well understood -resulting in rather catastrophic disasters in the past1 and thereby a significant burden on safety in using ammonium nitrates even today. To remedy this situation, we have carried out an extensive study to investigate the phase stability of AN at high pressure and temperature, using diamond anvil cells and micro-Raman spectroscopy. The present results confirm the recently proposed phase IV-to-IV' transition above 17 GPa2 and provide new constraints for the melting and phase diagram of AN to 40 GPa and 400 °C.

Dunuwille, M.; Yoo, C. S.

2014-05-01

200

High performance ammonium nitrate propellant  

NASA Technical Reports Server (NTRS)

A high performance propellant having greatly reduced hydrogen chloride emission is presented. It is comprised of: (1) a minor amount of hydrocarbon binder (10-15%), (2) at least 85% solids including ammonium nitrate as the primary oxidizer (about 40% to 70%), (3) a significant amount (5-25%) powdered metal fuel, such as aluminum, (4) a small amount (5-25%) of ammonium perchlorate as a supplementary oxidizer, and (5) optionally a small amount (0-20%) of a nitramine.

Anderson, F. A. (inventor)

1979-01-01

201

Photochemical reduction of uranyl nitrate  

SciTech Connect

The photochemical reduction of uranyl nitrate solutions to tetravalent uranium was investigated as a means of producing uranium dioxide feed for the saltless direct oxide reduction (SDOR) process. At high uranium concentrations, reoxidation of U{sup +4} occurs rapidly. The kinetics of the nitric oxidation of tetravalent uranium depend on the concentrations of hydrogen ion, nitrate ion, nitrous acid, and tetravalent uranium in the same manner as was reported elsewhere for the nitrate oxidation of PU{sup +3}. Reaction rate data were successfully correlated with a mechanism in which nitrogen dioxide is the reactive intermediate. Addition of a nitrous acid scavenger suppresses the reoxidation reaction. An immersion reactor employing a mercury vapor lamp gave reduction times fast enough for routine production usage. Precipitation techniques for conversion of aqueous U(NO{sub 3}){sub 4} to hydrous UO{sub 2} were evaluated. Prolonged dewatering times tended to make the process time consuming. Use of 3- to 4-M aqueous NaOH gave the best dewatering times observed. Reoxidation of the UO{sub 2} by water of hydration was encountered, which required the drying process to be carried out under a reducing atmosphere.

Duerksen, W.K.

1993-10-20

202

Electrolytic production of uranous nitrate  

SciTech Connect

Efficient production of uranous nitrate is important in nuclear fuel reprocessing because U(IV) acts as a plutonium reductant in solvent extraction and can be coprecipitated with plutonium and/or throium as oxalates during fuel reprocessing. Experimental conditions are described for the efficient electrolytic production of uranous nitrate for use as a reductant in the SRP Purex process. The bench-scale, continuous-flow, electrolysis cell exhibits a current efficiency approaching 100% in combination with high conversion rates of U(VI) to U(IV) in simulated and actual SRP Purex solutions. High current efficiency is achieved with a voltage-controlled mercury-plated platinum electrode and the use of hydrazine as a nitrite scavenger. Conversion of U(VI) to U(IV) proceeds at 100% efficiency. Cathodic gas generation is minimal. The low rate of gas generation permits a long residence time within the cathode, a necessary condition for high conversions on a continuous basis. Design proposals are given for a plant-scale, continuous-flow unit to meet SRP production requirements. Results from the bench-scale tests indicate that an 8-kW unit can supply sufficient uranous nitrate reductant to meet the needs of the Purex process at SRP.

Orebaugh, E.G.; Propst, R.C.

1980-04-01

203

Thermochemistry of amorphous and crystalline zirconium and hafnium silicates.  

NASA Astrophysics Data System (ADS)

Calorimetric investigation of amorphous and crystalline zirconium and hafnium silicates was performed as part of a research program on thermochemistry of alternative gate dielectrics. Amorphous hafnium and zirconium silicates with varying SiO2 content were synthesized by a sol-gel process. Crystalline zirconium and hafnium silicates (zircon and hafnon) were synthesized by solid state reaction at 1450 °C from amorphous gels and grown as single crystals from flux. High temperature oxide melt solution calorimetry in lead borate (2PbO.B2O3) solvent at 800 oC was used to measure drop solution enthalpies for amorphous and crystalline zirconium and hafnium silicates and corresponding oxides. Applying appropriate thermochemical cycles, formation enthalpy of crystalline ZrSiO4 (zircon) from binary oxides (baddeleite and quartz) at 298 K was calculated as -23 +/-2 kJ/mol and enthalpy difference between amorphous and crystalline zirconium silicate (vitrification enthalpy) was found to be 61 +/-3 kJ/mol. Crystallization onset temperatures of amorphous zirconium and hafnium silicates, as measured by differential scanning calorimetry (DSC), increased with silica content. The resulting crystalline phases, as characterized by X-ray diffraction (XRD), were tetragonal HfO2 and ZrO2. Critical crystallite size for tetragonal to monoclinic transformation of HfO2 in the gel was estimated as 6 +/-2 nm from XRD data Crystallization enthalpies per mole of hafnia and zirconia in gels decrease slightly together with crystallite size with increasing silica content, for example from -22 to -15 +/-1 kJ per mol of HfO2 crystallized at 740 and 1006 °C from silicates with 10 and 70 mol Applications of thermal analyses and solution calorimetry techniques together with first-principles density functional calculations to estimate interface and surface energies are discussed.

Ushakov, S.; Brown, C. E.; Navrotsky, Alexandra; Boatner, L. A.; Demkov, A. A.; Wang, C.; Nguyen, B.-Y.

2003-03-01

204

Chemistry of zirconium related to the behavior of nuclear fuel cladding. Final report  

SciTech Connect

Studies of the chemistry of the zirconium-iodine and zirconium-oxygen systems were undertaken to elucidate their thermodynamics and kinetics. It is anticipated that the results obtained will lead to an improved understanding of the chemical processes involved in chemically assisted fuel rod failures. This project not only has classified the thermodynamics of both the gas phase and the solids in the zirconium-iodine system, it has also provided valuable information on the chemisorption of iodine and of oxygen on zirconium surfaces at high temperatures. In addition, the kinetics of reactions on zirconium surfaces were studied. These results have already been helpful in understanding the stress corrosion cracking of Zircaloy.

Cubicciotti, D.

1980-03-26

205

Zirconium diboride nanofiber generation via microwave arc heating.  

PubMed

Ultrahigh temperature zirconium diboride nanofibers were produced by microwave arc heating using micron-sized raw powder. While microwave heating the ZrB(2) powder, the development of local arcing led to rapid heating and solidification of the samples, along with the creation of nanofibers. The morphology of these high aspect ratio nanofibers was characterized using scanning electron microscopy and transmission electron microscopy. Energy dispersive x-ray spectroscopy, electron energy loss spectroscopy and selected area electron diffraction showed the composition to contain zirconium, boron, nitrogen, aluminum and oxygen as well as the crystallographic orientation. ZrB(2) nanofiber applications include aerospace and other harsh environments. PMID:21828708

Baldridge, Tyson; Gupta, Mool C

2008-07-01

206

Zirconium diboride nanofiber generation via microwave arc heating  

NASA Astrophysics Data System (ADS)

Ultrahigh temperature zirconium diboride nanofibers were produced by microwave arc heating using micron-sized raw powder. While microwave heating the ZrB2 powder, the development of local arcing led to rapid heating and solidification of the samples, along with the creation of nanofibers. The morphology of these high aspect ratio nanofibers was characterized using scanning electron microscopy and transmission electron microscopy. Energy dispersive x-ray spectroscopy, electron energy loss spectroscopy and selected area electron diffraction showed the composition to contain zirconium, boron, nitrogen, aluminum and oxygen as well as the crystallographic orientation. ZrB2 nanofiber applications include aerospace and other harsh environments.

Baldridge, Tyson; Gupta, Mool C.

2008-07-01

207

In-situ stabilization of radioactive zirconium swarf  

DOEpatents

The method for treating ignitable cutting swarf in accordance with the present invention involves collecting cutting swarf in a casting mold underwater and injecting a binder mixture comprising vinyl ester styrene into the vessel to fill void volume; and form a mixture comprising swarf and vinyl ester styrene; and curing the mixture. The method is especially useful for stabilizing the ignitable characteristics of radioactive zirconium cutting swarf, and can be used to solidify zirconium swarf, or other ignitable finely divided material, underwater. The process could also be performed out of water with other particulate wastes.

Hess, Clay C. (Idaho Falls, ID)

1999-01-01

208

In-situ stabilization of radioactive zirconium swarf  

DOEpatents

The method for treating ignitable cutting swarf in accordance with the present invention involves collecting cutting swarf in a casting mold underwater and injecting a binder mixture comprising vinyl ester styrene into the vessel to fill void volume; and form a mixture comprising swarf and vinyl ester styrene; and curing the mixture. The method is especially useful for stabilizing the ignitable characteristics of radioactive zirconium cutting swarf, and can be used to solidify zirconium swarf, or other ignitable finely divided material, underwater. The process could also be performed out of water with other particulate wastes. 6 figs.

Hess, C.C.

1999-08-31

209

Heavy Ion Irradiation Effects in Zirconium Nitride  

SciTech Connect

Polycrystalline zirconium nitride (ZrN) samples were irradiated with He{sup +}, Kr{sup ++}, and Xe{sup ++} ions to high (>1.10{sup 16} ions/cm{sup 2}) fluences at {approx}100 K. Following ion irradiation, transmission electron microscopy (TEM) and grazing incidence X-ray diffraction (GIXRD) were used to analyze the microstructure and crystal structure of the post-irradiated material. For ion doses equivalent to approximately 200 displacements per atom (dpa), ZrN was found to resist any amorphization transformation, based on TEM observations. At very high displacement damage doses, GIXRD measurements revealed tetragonal splitting of some of the diffraction maxima (maxima which are associated with cubic ZrN prior to irradiation). In addition to TEM and GIXRD, mechanical property changes were characterized using nano-indentation. Nano-indentation revealed no change in elastic modulus of ZrN with increasing ion dose, while the hardness of the irradiated ZrN was found to increase significantly with ion dose. Finally, He{sup +} ion implanted ZrN samples were annealed to examine He gas retention properties of ZrN as a function of annealing temperature. He gas release was measured using a residual gas analysis (RGA) spectrometer. RGA measurements were performed on He-implanted ZrN samples and on ZrN samples that had also been irradiated with Xe{sup ++} ions, in order to introduce high levels of displacive radiation damage into the matrix. He evolution studies revealed that ZrN samples with high levels of displacement damage due to Xe implantation, show a lower temperature threshold for He release than do pristine ZrN samples. (authors)

Egeland, G.W.; Bond, G.M. [New Mexico Institute of Mining and Technology, Socorro, NM 87801 (United States); Valdez, J.A.; Swadener, J.G.; McClellan, K.J.; Maloy, S.A.; Sickafus, K.E. [Los Alamos National Lab (United States); Oliver, B. [Pacific Northwest National Lab (United States)

2004-07-01

210

Effect of nitrate on microbial perchlorate reduction  

NASA Astrophysics Data System (ADS)

Over the last decade perchlorate has been recognized as an important emerging water contaminant that poses a significant public health threat. Because of its chemical stability, low ionic charge density, and significant water solubility microbial remediation has been identified as the most feasible method for its in situ attenuation. Our previous studies have demonstrated that dissimilatory perchlorate reducing bacteria (DPRB) capable of the respiratory reduction of perchlorate into innocuous chloride are ubiquitous in soil and sedimentary environments. As part of their metabolism these organisms reduce perchlorate to chlorite which is subsequently dismutated into chloride and molecular oxygen. These initial steps are mediated by the perchlorate reductase and chlorite dismutase enzymes respectively. Previously we found that the activity of these organisms is dependent on the presence of molybdenum and is inhibited by the presence of oxygen and to different extents nitrate. However, to date, there is little understanding of the mechanisms involved in the regulation of perchlorate reduction by oxygen and nitrate. As a continuation of our studies into the factors that control DPRB activity we investigated these regulatory mechanisms in more detail as a model organism, Dechloromonas aromatica strain RCB, transitions from aerobic metabolism through nitrate reduction to perchlorate reduction. In series of growth transition studies where both nitrate and perchlorate were present, preference for nitrate to perchlorate was observed regardless of the nitrate to perchlorate ratio. Even when the organism was pre-grown anaerobically in perchlorate, nitrate was reduced prior to perchlorate. Using non-growth washed cell suspension, perchlorate- grown D. aromatica was capable of reducing both perchlorate and nitrate concomitantly suggesting the preferentially utilization of nitrate was not a result of enzyme functionality. To elucidate the mechanism for preferential utilization of nitrate, transcripts of perchlorate reductase and chlorite dismutase were analyzed to determine possible transcriptional regulation from nitrate. During growth transition studies, increase in the level of transcripts necessary for nitrate reduction and perchlorate reduction was observed concomitantly with decrease in the concentration of nitrate and perchlorate respectively suggesting transcriptional regulation was involved in the preferential utilization of nitrate and that nitrate might be a transcriptional inhibitor of perchlorate reduction. Again, using non-growth washed cell suspensions of perchlorate grown D. aromatica, a decrease of transcript level of the perchlorate reductase but not the chlorite dismutase was observed after incubation with nitrate. In conclusion, from physiological and molecular evidence, nitrate negatively regulates transcription of perchlorate reductase thus inhibiting perchlorate reduction. This result is unexpected as it is in contrast to the accepted dogma that microorganisms regulate their metabolisms to utilize electron acceptors in a sequential manner based on thermodynamic optimization which would imply that perchlorate should be used preferentially to nitrate.

Sun, Y.; Coates, J. D.

2007-12-01

211

Anharmonic effects in ammonium nitrate and hydroxylammonium nitrate clusters.  

PubMed

The covalent and ionic clusters of ammonium nitrate and hydroxyl ammonium nitrate are characterized using density functional theory and second-order vibrational perturbation theory. The most stable structures are covalent acid-base pairs for the monomers and ionic acid-base pairs for the dimers. The hydrogen-bonding distances are greater in the ionic dimers than in the covalent monomers, and the stretching frequencies are significantly different in the covalent and ionic clusters. The anharmonicity of the potential energy surfaces is found to influence the geometries, frequencies, and nuclear magnetic shielding constants for these systems. The inclusion of anharmonic effects significantly decreases many of the calculated vibrational frequencies in these clusters and improves the agreement of the calculated frequencies with the experimental data available for the isolated neutral species. The calculations of nuclear magnetic shielding constants for all nuclei in these clusters illustrate that quantitatively accurate predictions of nuclear magnetic shieldings for comparison to experimental data require the inclusion of anharmonic effects. These calculations of geometries, frequencies, and shielding constants provide insight into the significance of anharmonic effects in ionic materials and provide data that will be useful for the parametrization of molecular mechanical force fields for ionic liquids. Anharmonic effects will be particularly important for the study of proton transfer reactions in ionic materials. PMID:17474693

Kumarasiri, Malika; Swalina, Chet; Hammes-Schiffer, Sharon

2007-05-10

212

Physiological aspects of ammonium and nitrate fertilization  

Microsoft Academic Search

Various physiological effects of ammonium, nitrate and mixed ammonium?nitrate nutrition of plants have been studied in this laboratory during the last years. Some of the characteristic distinctions observed between plants growing on these nitrogen sources are described and discussed. Biomass production of ammonium?grown plants increased with K concentration in the nutrient medium between 0.1 to 3 mM , while nitrate?fed

S. H. Lips; E. O. Leidi; M. Silberbush; M. I. M. Soares; O. E. M. Lewis

1990-01-01

213

Electronic structure and chemical bonding in nonstoichiometric zirconium nitrides  

Microsoft Academic Search

X-ray emission spectra were taken and band calculations using the Green function LMTO method and cluster calculations using the discrete variational Xa method were carried out for the electronic structure and chemical bonding parameters for nonstoichiometric zirconium nitrides containing metallic and metalloid vacancies. The existence of structural defects leads to a redistribution of the occupancies of the major sub-bands of

D. L. Novikov; Yu. M. Yarmoshenko; A. L. Ivanovskii; V. A. Gubanov

1989-01-01

214

Study of the Oxidation Behavior of Zirconium and Its Alloys.  

National Technical Information Service (NTIS)

The oxidation behavior of zirconium, Zircaloy-4 and Zr-2,5% Nb alloy, as well as the influence of temperature, oxidising atmosphere, metal composition, heat treatment, surface treatment and specimen size on the oxidation of these materials in the temperat...

I. Costa

1985-01-01

215

Regularities of sintering of zirconium diboride-molybenum alloys  

Microsoft Academic Search

In the process of sintering of mixtures of zirconium diboride with 5, 10, and 15% Mo, specimen growth resulting from heterodiffusion is observed at the instant of formation of solid solution of Mo in ZrB2 during slow heating to high temperatures or during the initial period of isothermal holding in the case of very rapid heating. At temperatures of up

P. S. Kislyi; M. A. Kuzenkova

1966-01-01

216

Casting Titanium and Zirconium in Zircon Sand Molds.  

National Technical Information Service (NTIS)

A zircon sand molding process was developed by the Bureau of Mines for static casting small titanium or zirconium shapes. Castings with unfinished weights up to 3.5 kg (7.7 lb) were produced in an inductoslag furnace and castings up to 7 kg (15.4 lb) were...

J. L. Hoffman M. L. Transue R. A. Beall R. K. Koch

1977-01-01

217

Stress measurements during thin film zirconium oxide growth  

Microsoft Academic Search

Stress accumulation during thin film zirconium oxide growth was successfully measured using new curvature measurement technique and stress of up to 5.1GPa was observed in an approximately 50nm thick oxide film. Experimental results also show that steam and air oxidation make little difference in the stress profile on the oxide film thickness, especially during the early stage of oxidation. This

Yong-Soo Kim; Yong-Hwan Jeong; Jeong-Nam Jang

2011-01-01

218

Method for applying corrosion resistant metallic coating of zirconium nitride  

SciTech Connect

A process is described for enhancing the wear and corrosion resistance of a cladding tube for a nuclear fuel rod, comprising reactively depositing zirconium nitride on the surface of said cladding tube by a cathodic arc plasma deposition process to form a thin wear resistant coating.

Bryan, W.J.; Corsetti, L.V.

1993-07-13

219

Studies on the Characteristic of Zirconium-Tritium Reaction  

NASA Astrophysics Data System (ADS)

The p- c-T curves of tritium absorption and desorption of zirconium were measured using the method of step equilibrium by stepping up the tritium quantity on an experimental apparatus of metal hydride. The p- c-T curves for tritium have one plateau at temperature range from 450 to 500°C and two plateaus at temperature above 600°C. The thermodynamic parameters of the different phases were determined according to the van't Hoff equation. The hysteresis effect was observed in reversible process of tritium absorption and desorption of zirconium on our experimental condition. The tritium absorption behavior by zirconium in the temperature range from 450 to 620°C and desorption behavior of zirconium in the temperature range from 775 to 875°C have been investigated. A method of the reaction rate analysis was proposed and examined for determining the rate constant. The apparent activation energy obtained by this analysis for the absorption and the desorption were (-16.8 ± 0.8) kJ·mol-1 and (57.7 ± 1.6) kJ·mol-1, respectively.

Huang, Gang; Long, Xing-Gui; Peng, Shu-Ming; Liang, Jian-Hua; Yang, Ben-Fu

2011-02-01

220

Study of Zirconium Dioxide White Pigment for Space Environment.  

National Technical Information Service (NTIS)

The properties of zirconium dioxide as a stable white pigment (low alpha/epsilon) for space application are investigated. First, the optical absorption of single crystals is studied, leading to the conclusion that a high degree of purity, except for hafni...

H. K. A. Kan R. J. Champetier T. G. Erler

1970-01-01

221

Sarcoid granulomatosis after zirconium exposure with multiple organ involvement  

Microsoft Academic Search

To the Editor: A 51 yr old, nonsmoking female suffered from relaps- ing progressive pneumonia for several years. The patient had worked for 16 yrs in the nuclear industry and was exposed to grinding particles and welding fumes working with zirkaloy, an alloy containing tin, iron, chromium and zirconium. During an exacerbation of the pneumonia radi- ography of the lung

U. Werfel; J. Schneider; K. Rödelsperger; J. Kotter; W. Popp; H. J. Woitowitz; G. Zieger

1998-01-01

222

Electrochemical Deoxidation of Solid Zirconium Dioxide in Molten Calcium Chloride  

NASA Astrophysics Data System (ADS)

The reduction of zirconium dioxide pellets by electro-deoxidation in molten calcium chloride-calcium oxide (900 °C) has been studied. In this technique, the solid oxide is cathodically polarized against a graphite counter electrode under a constant applied potential. Unlike other metal oxides that have been reduced by this technique, only a small area around the cathodic current-collector wire was reduced to zirconium metal with zirconia pellets sintered at ~1100 °C; the rest of the sample was largely calcium zirconate. Pellets sintered above 1200 °C showed better reduction near the cathode wire and the reduction extended to the entire surface of the pellet with the passage of time. However, reduction of the inner core was found to be increasingly difficult, because the surface metal layer thickened on continuous electro-deoxidation. An analysis of the experimental results showed that the poor electrical conductivity of the intermediate compound, CaZrO3 and its blocky morphology inhibited the electro-deoxidation process. The increase in the sintering temperature of the pellet made it better conducting. However, the pores formed in the thick zirconium metal layer in such samples were too small for an ideal contact between the inner core and the molten electrolyte and hence the reduction of the inner core remained incomplete. Within the scope of this study, it is concluded that preforms with good grain growth and porosity are necessary for the electro-deoxidation of solid zirconium oxide.

Mohandas, K. S.; Fray, D. J.

2009-10-01

223

Zirconium Molybdate Gel as a Generator for Technetium-99M.  

National Technical Information Service (NTIS)

A new sup(99m)Tc generator based on zirconium molybdate gel is described. Essentially the gel is a cation ion exchanger which permits the elution of the pertechnetate ion. The high molybdenum content of this gel, its stability under self-irradiation, and ...

J. V. Evans M. E. Shying

1984-01-01

224

Oxidized zirconium: a potentially longer lasting hip implant  

Microsoft Academic Search

Because younger, more active patients are receiving total hip replacements, it is necessary to develop materials, which would increase the life span of the implants and challenge their wear potential under adverse conditions. Oxidized zirconium (OxZr) is a metal with the surface transformed to ceramic by oxidation that offers low fracture risk and excellent abrasion resistance. This study compared wear

V. Good; K. Widding; G. Hunter; D. Heuer

2005-01-01

225

Extraction of Zirconium from Zircon (A New Process).  

National Technical Information Service (NTIS)

A new process has been used for the extraction of zirconium from zircon. Caustic fritting was done in the presence of magnesium hydroxide carbonate and magnesium oxide. These additives decrease the amount of nitric acid soluble silica less than 1000 ppm. ...

K. A. Shahid D. Saeed S. Jan A. Masood J. Akhtar

1985-01-01

226

Kinetics of chemical interactions between zirconium alloys and stainless steels.  

National Technical Information Service (NTIS)

The chemical interaction kinetics of reactor core component zirconium alloys and stainless steels at high temperatures was examined. Interaction of as-received and preoxidized Zr1%Nb with X18H10T stainless steel used in WWER type nuclear reactors, and als...

J. Frecska L. Maroti L. Matus

1995-01-01

227

Manufacturing process to reduce large grain growth in zirconium alloys  

DOEpatents

A method of treating cold-worked zirconium alloys to reduce large grain gth during thermal treatment at temperatures above the recrystallization temperature of the alloy comprising heating the cold-worked alloy between about 1300.degree.-1350.degree. F. for 1 to 3 hours prior to treatment above its recrystallization temperature.

Rosecrans, Peter M. (Niskayuna, NY) [Niskayuna, NY

1987-01-01

228

Microfiltration Membranes with the Selective Layer Based on Zirconium Dioxide  

Microsoft Academic Search

The effect of zirconium dioxide – polymer (binder) composite on the quality of the microfiltration selective layer is studied. The conditions for deposition of the membrane layer and its drying and firing are established. The characteristics of the porous structure of the obtained membranes are considered.

G. G. Kagramanov; V. V. Nazarov; E. S. Lukin; E. M. Pershikova

2001-01-01

229

Trend Analyses of Nitrate in Danish Groundwater  

NASA Astrophysics Data System (ADS)

This presentation assesses the long-term development in the oxic groundwater nitrate concentration and nitrogen (N) loss due to intensive farming in Denmark. Firstly, up to 20-year time-series from the national groundwater monitoring network enable a statistically systematic analysis of distribution, trends and trend reversals in the groundwater nitrate concentration. Secondly, knowledge about the N surplus in Danish agriculture since 1950 is used as an indicator of the potential loss of N. Thirdly, groundwater recharge CFC (Chlorofluorocarbon) age determination allows linking of the first two dataset. The development in the nitrate concentration of oxic groundwater clearly mirrors the development in the national agricultural N surplus, and a corresponding trend reversal is found in groundwater. Regulation and technical improvements in the intensive farming in Denmark have succeeded in decreasing the N surplus by 40% since the mid 1980s while at the same time maintaining crop yields and increasing the animal production of especially pigs. Trend analyses prove that the youngest (0-15 years old) oxic groundwater shows more pronounced significant downward nitrate trends (44%) than the oldest (25-50 years old) oxic groundwater (9%). This amounts to clear evidence of the effect of reduced nitrate leaching on groundwater nitrate concentrations in Denmark. Are the Danish groundwater monitoring strategy obtimal for detection of nitrate trends? Will the nitrate concentrations in Danish groundwater continue to decrease or are the Danish nitrate concentration levels now appropriate according to the Water Framework Directive?

Hansen, B.; Thorling, L.; Dalgaard, T.; Erlandsen, M.

2012-04-01

230

Photochemistry of Nitrate Adsorbed on Mineral Dust  

NASA Astrophysics Data System (ADS)

Mineral dust particles in the atmosphere are often associated with adsorbed nitrate from heterogeneous reactions with nitrogen oxides including HNO3 and NO2. Although nitrate ion is a well-studied chromophore in natural waters, the photochemistry of adsorbed nitrate on mineral dust particles is yet to be fully explored. In this study, wavelength dependence of the photochemistry of adsorbed nitrate on different model components of mineral dust aerosol has been investigated using transmission FTIR spectroscopy. Al2O3, TiO2 and NaY zeolite were used as model systems to represent non-photoactive oxides, photoactive semiconductor oxides and porous materials respectively, present in mineral dust aerosol. In this study, adsorbed nitrate is irradiated with 254 nm, 310 nm and 350 nm narrow band light. In the irradiation with narrow band light, NO2 is the only detectable gas-phase product formed from nitrate adsorbed on Al2O3 and TiO2. The NO2 yield is highest at 310 nm for both Al2O3 and TiO2. Unlike Al2O3 and TiO2, in zeolite, adsorbed nitrate photolysis to nitrite is observed only at 310 nm during narrow band irradiation. Moreover gas phase products were not detected during nitrate photolysis in zeolite at all three wavelengths. The significance of these differences as related to nitrate photochemistry on different mineral dust components will be highlighted.

Gankanda, A.; Grassian, V. H.

2013-12-01

231

The negative effect of nitrate on gametogenesis is independent of nitrate assimilation in Chlamydomonas reinhardtii  

Microsoft Academic Search

.  ?The effect of nitrate on gamete differentiation as well as on the expression of genes involved in gametogenesis, nitrogen\\u000a scavenging, and nitrate assimilation has been analyzed in wild-type and mutant strains of Chlamydomonas reinhardtii. Nitrate prevented gamete formation from wild-type strains and caused a strong reduction in the number of zygotes recovered\\u000a in genetic crosses between nitrate-assimilation-deficient mutants, thus suggesting

Mercedes Pozuelo; Faustino Merchán; María Isabel Macías; Christoph F. Beck; Aurora Galván; Emilio Fernández

2000-01-01

232

REDUCTION OF NITRATE THROUGH THE USE OF NITRATE REDUCTASE FOR THE SMARTCHEM AUTOANALYZER  

EPA Science Inventory

The standard method for the determination of nitrate in drinking water, USEPA Method 353.2 ¿Determination of Nitrate-Nitrite by Automated Colorimetry,¿ employs cadmium as the reductant for the conversion of nitrate to nitrite. The nitrite is then analyzed colorimetrically by way ...

233

Rapid colorimetric determination of nitrate in plant tissue by nitration of salicylic acid  

Microsoft Academic Search

An analysis is described for the rapid determination of nitrate?N in plant extracts. The complex formed by nitration of salicylic acid under highly acidic conditions absorbs maximally at 410 nm in basic (pH>12) solutions. Absorbance of the chromophore is directly proportional to the amount of nitrate?N present. Ammonium, nitrite, and chloride ions do not interfere.

D. A. Cataldo; M. Maroon; L. E. Schrader; V. L. Youngs

1975-01-01

234

Challenges with nitrate therapy and nitrate tolerance: prevalence, prevention, and clinical relevance.  

PubMed

Nitrate therapy has been an effective treatment for ischemic heart disease for over 100 years. The anti-ischemic and exercise-promoting benefits of sublingually administered nitrates are well established. Nitroglycerin is indicated for the relief of an established attack of angina and for prophylactic use, but its effects are short lived. In an effort to increase the duration of beneficial effects, long-acting orally administered and topical applications of nitrates have been developed; however, following their continued or frequent daily use, patients soon develop tolerance to these long-acting nitrate preparations. Once tolerance develops, patients begin losing the protective effects of the long-acting nitrate therapy. By providing a nitrate-free interval, or declining nitrate levels at night, one can overcome or reduce the development of tolerance, but cannot provide 24-h anti-anginal and anti-ischemic protection. In addition, patients may be vulnerable to occurrence of rebound angina and myocardial ischemia during periods of absent nitrate levels at night and early hours of the morning, and worsening of exercise capacity prior to the morning dose of the medication. This has been a concern with nitroglycerin patches but not with oral formulations of isosorbide-5 mononitrates, and has not been adequately studied with isosorbide dinitrate. This paper describes problems associated with nitrate tolerance, reviews mechanisms by which nitrate tolerance and loss of efficacy develop, and presents strategies to avoid nitrate tolerance and maintain efficacy when using long-acting nitrate formulations. PMID:24664980

Thadani, Udho

2014-08-01

235

Electrochemical stripping determination of traces of copper, lead, cadmium and zinc in zirconium metal and zirconium dioxide.  

PubMed

Procedures have been developed for the determination of copper, lead, cadmium and zinc in zirconium metal and zirconium dioxide, at concentrations of 1 ppm or less. Zirconium metal was dissolved in suphuric acid, and zirconium dioxide decomposed under pressure with hydrofluoric acid. Sample solutions were prepared in dilute sulphuric acid. For the stripping determination, the sample solution was either mixed with a complexing tartrate base electrolyte or the pre-electrolysis was carried out in acid solution, with the acid solution being exchanged for a pure base electrolyte (e.g. an acetate buffer) for the stripping step. The stripping step was monitored by d.c., differential pulse and Kalousek commutator voltammetry and the three methods were compared. A stationary mercury-drop electrode can generally be used for all the methods, whereas a mercury-film electrode is suitable only for the d.c. voltammetric determination of copper, lead and cadmium, as pulse measurements with films are poorly reproducible and the electrodes are easily damaged. The relative standard deviation does not exceed 20%. Some samples contained relatively large amounts of copper, which is best separated by electrodeposition on a platinum electrode. PMID:18962277

Stulík, K; Beran, P; Dolezal, J; Opekar, F

1978-07-01

236

Nitrite and Nitrate in Cancer  

Microsoft Academic Search

\\u000a \\u000a \\u000a \\u000a \\u000a \\u000a • \\u000a \\u000a \\u000a \\u000a Studies in animal models established the feasibility of sodium nitrite contributing to gastric carcinogenesis primarily via\\u000a conversion to nitrosamines.\\u000a \\u000a \\u000a \\u000a \\u000a \\u000a • \\u000a \\u000a \\u000a \\u000a Most animal studies did not corroborate this assumption.\\u000a \\u000a \\u000a \\u000a \\u000a • \\u000a \\u000a \\u000a \\u000a Exposure of humans to nitrates is primarily from vegetables.\\u000a \\u000a \\u000a \\u000a \\u000a • \\u000a \\u000a \\u000a \\u000a Since a fraction of nitrate is reduced to nitrite by oral bacteria, the largest source of nitrite exposure is also

David M. Klurfeld

237

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

238

Nitrate Reduction Functional Genes and Nitrate Reduction Potentials Persist in Deeper Estuarine Sediments. Why?  

PubMed Central

Denitrification and dissimilatory nitrate reduction to ammonium (DNRA) are processes occurring simultaneously under oxygen-limited or anaerobic conditions, where both compete for nitrate and organic carbon. Despite their ecological importance, there has been little investigation of how denitrification and DNRA potentials and related functional genes vary vertically with sediment depth. Nitrate reduction potentials measured in sediment depth profiles along the Colne estuary were in the upper range of nitrate reduction rates reported from other sediments and showed the existence of strong decreasing trends both with increasing depth and along the estuary. Denitrification potential decreased along the estuary, decreasing more rapidly with depth towards the estuary mouth. In contrast, DNRA potential increased along the estuary. Significant decreases in copy numbers of 16S rRNA and nitrate reducing genes were observed along the estuary and from surface to deeper sediments. Both metabolic potentials and functional genes persisted at sediment depths where porewater nitrate was absent. Transport of nitrate by bioturbation, based on macrofauna distributions, could only account for the upper 10 cm depth of sediment. A several fold higher combined freeze-lysable KCl-extractable nitrate pool compared to porewater nitrate was detected. We hypothesised that his could be attributed to intracellular nitrate pools from nitrate accumulating microorganisms like Thioploca or Beggiatoa. However, pyrosequencing analysis did not detect any such organisms, leaving other bacteria, microbenthic algae, or foraminiferans which have also been shown to accumulate nitrate, as possible candidates. The importance and bioavailability of a KCl-extractable nitrate sediment pool remains to be tested. The significant variation in the vertical pattern and abundance of the various nitrate reducing genes phylotypes reasonably suggests differences in their activity throughout the sediment column. This raises interesting questions as to what the alternative metabolic roles for the various nitrate reductases could be, analogous to the alternative metabolic roles found for nitrite reductases.

Papaspyrou, Sokratis; Smith, Cindy J.; Dong, Liang F.; Whitby, Corinne; Dumbrell, Alex J.; Nedwell, David B.

2014-01-01

239

Nitrate reduction functional genes and nitrate reduction potentials persist in deeper estuarine sediments. Why?  

PubMed

Denitrification and dissimilatory nitrate reduction to ammonium (DNRA) are processes occurring simultaneously under oxygen-limited or anaerobic conditions, where both compete for nitrate and organic carbon. Despite their ecological importance, there has been little investigation of how denitrification and DNRA potentials and related functional genes vary vertically with sediment depth. Nitrate reduction potentials measured in sediment depth profiles along the Colne estuary were in the upper range of nitrate reduction rates reported from other sediments and showed the existence of strong decreasing trends both with increasing depth and along the estuary. Denitrification potential decreased along the estuary, decreasing more rapidly with depth towards the estuary mouth. In contrast, DNRA potential increased along the estuary. Significant decreases in copy numbers of 16S rRNA and nitrate reducing genes were observed along the estuary and from surface to deeper sediments. Both metabolic potentials and functional genes persisted at sediment depths where porewater nitrate was absent. Transport of nitrate by bioturbation, based on macrofauna distributions, could only account for the upper 10 cm depth of sediment. A several fold higher combined freeze-lysable KCl-extractable nitrate pool compared to porewater nitrate was detected. We hypothesised that his could be attributed to intracellular nitrate pools from nitrate accumulating microorganisms like Thioploca or Beggiatoa. However, pyrosequencing analysis did not detect any such organisms, leaving other bacteria, microbenthic algae, or foraminiferans which have also been shown to accumulate nitrate, as possible candidates. The importance and bioavailability of a KCl-extractable nitrate sediment pool remains to be tested. The significant variation in the vertical pattern and abundance of the various nitrate reducing genes phylotypes reasonably suggests differences in their activity throughout the sediment column. This raises interesting questions as to what the alternative metabolic roles for the various nitrate reductases could be, analogous to the alternative metabolic roles found for nitrite reductases. PMID:24728381

Papaspyrou, Sokratis; Smith, Cindy J; Dong, Liang F; Whitby, Corinne; Dumbrell, Alex J; Nedwell, David B

2014-01-01

240

Syntheses and structural characterization of zirconium-tin and zirconium-lead binary and ternary systems  

SciTech Connect

The binary zirconium-tin system was reinvestigated. The A15 phase appears to be a line phase with a Zr{sub 4}Sn composition. The Zr{sub 5}Sn{sub 3} (Mn{sub 5}Si{sub 3}-type) and Zr{sub 5}Sn{sub 4} (Ti{sub 5}Ga{sub 4}-type) compounds are line phases below 1000{degree}C, the latter being a self-interstitial phase of the former. ZrSn{sub 2} is the tin-richest phase. There is an one-phase region between these phases with partial self-interstitials at high temperatures. The zirconium-lead system behaves similarly: there are an A15 phase with a Zr{sub {approximately}5.8}Pb composition, Zr{sub 5}Pb{sub 3} (Mn{sub 5}Si{sub 3}-type) and Zr{sub 5}Pb{sub 4} (Ti{sub 5}Ga{sub 4-type}) compounds, and a high temperature solid solution between Zr{sub 5}Pb{sub >3.5} and Zr{sub 5}Pb{sub 4} from below 1000{degree}C; however, the ZrSn{sub 2} analogue is not formed. The Mn{sub 5}Si{sub 3}-type phases in these systems can accommodate third elements interstitially to form stoichiometric compounds Zr{sub 5}Sn{sub 3}Z (Z = B, C, N, O, Al, Si, P, S, Cu, Zn, Ga, Ge, and As and Se) and Zr{sub 5}Pb{sub 3}Z (Z = Al, Si, P, S, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Se, Ag, Cd, In, Sn, Sb and Te) as well as their self-interstitial derivatives. The systems Zr-Sn-T, T = Fe, Co and Ni, did not produce stoichiometric interstitial phases Zr{sub 5}Sn{sub 3}T. Instead, the interstitial phases for these elements are formed only with excess tin that partially occupies the interstitial site together with a T element. Reducing the amount of tin in these systems yields two new phases; Zr{sub 5}Sn{sub 2+x}Fe{sub 1-x} (0 {le} {times} {le} 0.28) (W{sub 5}Si{sub 3}-type) and Zr{sub 6}Sn{sub 2}Fe (Zr{sub 6}Al{sub 2}Co-type) as characterized by X-ray single crystal analyses. A cobalt analogue for the latter was also synthesized.

Kwon, Y.U.

1991-01-28

241

The contributions of nitrate uptake and efflux to isotope fractionation during algal nitrate assimilation  

NASA Astrophysics Data System (ADS)

In order to strengthen environmental application of nitrate N and O isotopes, we measured the N and O isotopic fractionation associated with cellular nitrate uptake and efflux in the nitrate-assimilating marine diatom Thalassiosira weissflogii. We isolated nitrate uptake and efflux from nitrate reduction by growing the cells in the presence of tungsten, which substitutes for molybdenum in assimilatory nitrate reductase, yielding an inactive enzyme. After growth on ammonium and then N starvation, cells were exposed to nitrate. Numerical models fit to the evolution of intracellular nitrate concentration and N and O isotopic composition yielded distinct N isotope effects (15?) for nitrate uptake and nitrate efflux (2.0 ± 0.3‰ and 1.2 ± 0.4‰, respectively). The O isotope effects (18?) for nitrate uptake and nitrate efflux were indistinguishable (2.8 ± 0.6‰), yielding a ratio of O to N isotopic fractionation for uptake of 1.4 ± 0.4 and for efflux of 2.3 ± 0.9. The 15? for nitrate uptake can account for at most 40% of the organism-level N isotope effect (15?org) measured in laboratory studies of T. weissflogii and in the open ocean (typically 5‰ or greater). This observation supports previous evidence that most isotope fractionation during nitrate assimilation is due to intracellular nitrate reduction, with nitrate efflux allowing the signal to be communicated to the environment. An O to N fractionation ratio (18?org:15?org) of ˜1 has been measured for nitrate assimilation in algal cultures and linked to the N and O isotope effects of nitrate reductase. Our results suggest that the ratios of O to N fractionation for both nitrate uptake and efflux may be distinct from a ratio of 1, to a degree that could cause the net 18?org:15?org to rise appreciably above 1 when 15?org is low (e.g., yielding a ratio of 1.1 when 15?org is 5‰). However, field and culture studies have consistently measured nearly equivalent fractionation of N and O isotopes in association with low isotope effects, calling for isotopic studies of nitrate transport by other phytoplankton strains.

Karsh, K. L.; Trull, T. W.; Sigman, D. M.; Thompson, P. A.; Granger, J.

2014-05-01

242

21 CFR 172.170 - Sodium nitrate.  

Code of Federal Regulations, 2013 CFR

...HUMAN CONSUMPTION (CONTINUED) FOOD ADDITIVES PERMITTED FOR DIRECT ADDITION TO FOOD...172.170 Sodium nitrate. The food additive sodium nitrate may be safely used in...product. (b) To assure safe use of the additive, in addition to the other...

2013-04-01

243

Desensitizer for N-Propyl Nitrate.  

National Technical Information Service (NTIS)

According to this invention, n-propyl nitrate is rendered insensitive to shock, i.e., is desensitized, by means of a low gamma gas. The low gamma gas is incorporated into the n-propyl nitrate in an amount sufficient to assure that when bubbles are formed ...

B. A. Breslow

1976-01-01

244

COMPARTMENTAL MODEL OF NITRATE RETENTION IN STREAMS  

EPA Science Inventory

A compartmental modeling approach is presented to route nitrate retention along a cascade of stream reach sections. A process transfer function is used for transient storage equations with first order reaction terms to represent nitrate uptake in the free stream, and denitrifica...

245

Nitrate reductase in Peru current phytoplankton  

Microsoft Academic Search

Nitrate reductase (NR) activity was assayed by measuring the NADH-dependent formation of nitrite in phytoplankton extracts. NR specific activity increased with the nitrate concentration of the water in upwelling areas of the Peru Current. The temperature optimum for NR for natural phytoplankton was 15° to 20°C. NR activity showed diel periodicity, with maximum activity about noon and minimum activity near

R. W. Eppley; T. T. Packard; J. J. MacIsaac

1970-01-01

246

HEALTH EFFECTS OF NITRATES IN WATER  

EPA Science Inventory

A multi faceted study of the health effects of nitrate in drinking water using epidemiological and toxicological techniques is reported. The results of the epidemiological studies indicate that infants consuming appreciable amounts of water high in nitrates in the form of powdere...

247

Energy transfer in crystalline alkali nitrates  

NASA Astrophysics Data System (ADS)

The radiation annealing of peroxynitrite ions in pre-photolyzed (253.7 nm) alkali nitrate crystals has been studied. This process is stated to be due to interaction with high-energy excited states of the nitrate ion symmetry E' than to low-energy excited states symmetry A1?. The distance of energy transfer has been found to be ˜10 nm.

Anan'ev, Vladimir

2007-08-01

248

Winter Wheat Fertilization: Post Ammonium Nitrate  

Microsoft Academic Search

Summary The potential for overwinter losses of nitrogen by denitrification and leaching have led to the recommendation that nitrogen fertilization of winter wheat be done using ammonium nitrate broadcast in the spring. However, spring broadcast application of urea can result in significant loss of nitrogen by volatilization and immobilization by surface residues. Since prilled ammonium nitrate is not available for

R. Byron Irvine; Guy Lafond; Randy Kutcher

249

46 CFR 148.227 - Calcium nitrate fertilizers.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Calcium nitrate fertilizers. 148.227...Certain Materials § 148.227 Calcium nitrate fertilizers. This part does not apply to commercial grades of calcium nitrate fertilizers consisting...

2013-10-01

250

SAMPLING AND ANALYTICAL METHODOLOGY FOR ATMOSPHERIC PARTICULATE NITRATES  

EPA Science Inventory

Environmental conditions that affect atmospheric particulate nitrate sampling were identified, and improved sampling and analytical procedures were developed. Evaluation of potential sources of error in high volume nitrate sampling showed that artifact nitrate formation on common...

251

Method of purifying zirconium tetrachloride and hafnium tetrachloride in a vapor stream  

SciTech Connect

This patent describes a method of purifying zirconium tetrachloride and hafnium tetrachloride in a vapor stream from a sand chlorinator in which the silicon and metals present in sand fed to the chlorinator are converted to chlorides at temperatures over about 800{degrees} C. It comprises cooling a vapor stream from a sand chlorinator, the vapor stream containing principally silicon tetrachloride, zirconium tetrachloride, and hafnium tetrachloride contaminated with ferric chloride, to a temperature of from about 335{degrees} C to about 600{degrees} C; flowing the vapor stream through a gaseous diffusion separative barrier to produce a silicon tetrachloride-containing vapor stream concentrated in zirconium tetrachloride and hafnium tetrachloride and a silicon tetrachloride-containing vapor stream depleted in zirconium tetrachloride and hafnium tetrachloride; adsorbing the ferric chloride in the separative barrier; and recovering the silicon tetrachloride stream concentrated in zirconium tetrachloride and hafnium tetrachloride separately from the silicon tetrachloride stream depleted in zirconium tetrachloride and hafnium tetrachloride.

Snyder, T.S.; Stolz, R.A.

1992-04-07

252

Phase diagram of ammonium nitrate.  

PubMed

Ammonium Nitrate (AN) is a fertilizer, yet becomes an explosive upon a small addition of chemical impurities. The origin of enhanced chemical sensitivity in impure AN (or AN mixtures) is not well understood, posing significant safety issues in using AN even today. To remedy the situation, we have carried out an extensive study to investigate the phase stability of AN and its mixtures with hexane (ANFO-AN mixed with fuel oil) and Aluminum (Ammonal) at high pressures and temperatures, using diamond anvil cells (DAC) and micro-Raman spectroscopy. The results indicate that pure AN decomposes to N2, N2O, and H2O at the onset of the melt, whereas the mixtures, ANFO and Ammonal, decompose at substantially lower temperatures. The present results also confirm the recently proposed phase IV-IV' transition above 17 GPa and provide new constraints for the melting and phase diagram of AN to 40 GPa and 400°C. PMID:24320387

Dunuwille, Mihindra; Yoo, Choong-Shik

2013-12-01

253

Pseudo-constitutivity of nitrate-responsive genes in nitrate reductase mutants  

PubMed Central

In fungi, transcriptional activation of genes involved in NO3- assimilation requires the presence of an inducer (nitrate or nitrite) and low intracellular concentrations of the pathway products ammonium or glutamine. In Aspergillus nidulans, the two transcription factors NirA and AreA act synergistically to mediate nitrate/nitrite induction and nitrogen metabolite derepression, respectively. In all studied fungi and in plants, mutants lacking nitrate reductase (NR) activity express nitrate-metabolizing enzymes constitutively without the addition of inducer molecules. Based on their work in A. nidulans, Cove and Pateman proposed an “autoregulation control” model for the synthesis of nitrate metabolizing enzymes in which the functional nitrate reductase molecule would act as co-repressor in the absence and as co-inducer in the presence of nitrate. However, NR mutants could simply show “pseudo-constitutivity” due to induction by nitrate which accumulates over time in NR-deficient strains. Here we examined this possibility using strains which lack flavohemoglobins (fhbs), and are thus unable to generate nitrate internally, in combination with nitrate transporter mutations (nrtA, nrtB) and a GFP-labeled NirA protein. Using different combinations of genotypes we demonstrate that nitrate transporters are functional also in NR null mutants and show that the constitutive phenotype of NR mutants is not due to nitrate accumulation from intracellular sources but depends on the activity of nitrate transporters. However, these transporters are not required for nitrate signaling because addition of external nitrate (10 mM) leads to standard induction of nitrate assimilatory genes in the nitrate transporter double mutants. We finally show that NR does not regulate NirA localization and activity, and thus the autoregulation model, in which NR would act as a co-repressor of NirA in the absence of nitrate, is unlikely to be correct. Results from this study instead suggest that transporter-mediated NO3- accumulation in NR deficient mutants, originating from traces of nitrate in the media, is responsible for the constitutive expression of NirA-regulated genes, and the associated phenotype is thus termed “pseudo-constitutive”.

Schinko, Thorsten; Gallmetzer, Andreas; Amillis, Sotiris; Strauss, Joseph

2013-01-01

254

Preparation and properties of zirconium oxynitrides by the reaction of zirconia with layer structured zirconium nitrochloride  

SciTech Connect

Zirconium oxynitrides were prepared by the reaction of ZrO[sub 2]with layer structured [beta]-ZrNCl at temperatures in a range of 900-1,000C in an ammonia stream. In the reaction, [beta]-ZrNCl acted as a nitrogen source having a composition equivalent to ZrN[sub 4/3], although without the presence of the oxide it was converted into ZrN. Unlike the oxynitride formation from a conventional mixture of ZrN and ZrO[sub 2], the reaction was remarkably fast and completed within 30 min. Two kinds of oxynitride phases, [gamma] and [beta], were obtained, which have fluorite-related superstructures with a range of composition ZrN[sub 4x/3]O[sub 2[minus]2x] (0.5 [le] x [le] 0.8) and an ideal formula Zr[sub 7]N[sub 4]O[sub 8], respectively. Both of the phases are semiconductors with optical band gap energies of 2.50 to 3.20 eV.

Ohashi, Masao; Yamamoto, Hiroyuki; Yamanaka, Shoji; Hattori, Makoto (Hiroshima Univ., Higashi-Hiroshima (Japan))

1993-06-01

255

Penetrate-leach dissolution of zirconium-clad uranium and uranium dioxide fuels  

Microsoft Academic Search

A new decladding-dissolution process was developed for zirconium-clad uranium metal and UO fuels. The proposed penetrate-leach process consists of penetrating the zirconium cladding with Alniflex solution (2M HF--1M HNO--1M Al(NO)--0.1M KCrO) and of leaching the exposed core with 10M HNO. Undissolved cladding pieces are discarded as solid waste. Periodic HF and HNO additions, efficient agitation, and in-line zirconium analyses are

1975-01-01

256

Mechanical characterization of zirconium hydrides with high energy X-ray diffraction  

Microsoft Academic Search

Zirconium and its alloys are of technical importance, finding application as a structural material in the nuclear industry. Engineering components fabricated from zirconium slowly pick-up hydrogen as a result of in-reactor corrosion, degrading the components mechanical properties as a brittle hydride phase forms. This dissertation applies high energy X-ray diffraction to directly measure the mechanical properties of zirconium hydrides in

Matthew Kerr

2009-01-01

257

DELAYED FAILURE HYDROGEN EMBRITTLEMENT OF ZIRCONIUM. Summary Report, September 15, 1961 to September 14, 1962  

Microsoft Academic Search

The extent to which zirconium and zirconium alloys exhibit delayed ; failure (static fatigue) as caused by a combination of absorbed hydrogen and ; applied stress was investigated. Susceptibility to time-dependent fracture was ; evaluated for unalloyed zirconium and Zircaloy-2 with 200 and 500 ppm hydrogen as ; well as for an experimental Zr Al-Sn-Mo alloy and the Canadian Zr-2.5Nb

D. Weinstein; F. C. Holtz

1962-01-01

258

High cycle fatigue properties and microstructure of zirconium and zircaloy-4 under reversal bending  

Microsoft Academic Search

Fatigue lifetime curves of a commercial-purity zirconium and zircaloy-4 were measured under reversal bending. Scanning electron microscopic examination on surfaces of fatigued specimens shows that zirconium displays planar slip, whereas zircaloy-4 displays wavy slip. Fracture surface analysis shows that many fatigue striations with a considerable number of micro-cracks are the primary characters in zirconium and zircaloy-4. Fatigue crack generally nucleates

Xiao Lin; Gu Haicheng

1998-01-01

259

Contamination of silicon dioxide films by aqueous zirconium and hafnium species  

Microsoft Academic Search

Zirconium and hafnium oxides and silicates have emerged as potential replacements for SiO2 as gate dielectric material. Patterning of these materials by wet etching in fabrication areas originally designed for SiO2 gates may give rise to contamination of SiO2 by aqueous zirconium and hafnium species. This paper summarizes the work carried out to characterize the adsorption behavior of aqueous zirconium

V. Lowalekar; S. Raghavan; V. Pandit; H. G. Parks; J. Jeon

2006-01-01

260

Colloidal and chemical aspects of nanosized hydrated zirconium dioxide synthesized via a sol-gel process.  

PubMed

The processes of coagulation and gelation of sols in zirconium oxychloride aqueous solutions and the properties of hydrated zirconium dioxide sols (pH, particles size, dynamic viscosity) depending on the aging conditions of partially neutralized zirconium oxychloride feedstock solution-zirconyl hydroxychloride used for the synthesis and molar ratio of initial reagents (Zr/NaOH, Zr/CH(3)COO(-)) were first studied in the paper. The concentration and temperature limits of hydrated zirconium dioxide sols stability were determined. The coagulation constant, gelation activation energy, and gelation thermal effect values were found. PMID:21310423

Chepurna, Iryna; Smotraev, Roman; Kanibolotsky, Valentyn; Strelko, Volodymyr

2011-04-15

261

Stress corrosion cracking of zirconium used in the reprocessing plant  

SciTech Connect

We investigated stress corrosion cracking (SCC) of zirconium by constant load test and the small-scale mock-up test simulated the fuel dissolve. These tests operated in the simulated solution, which substituted non-radioactive elements, i.e. V with radioactive elements such as Pu and Np. From the results of constant load test, the cracks were not observed on 150 MPa after 908 hours in approximately 3 % strain. However a lot of cracks caused by SCC were observed over 20 % strain under high tensile stress in the simulated solution and the heat-transfer condition having more corrosive circumstance and noble potential accelerated the susceptibility of SCC. The cracking behavior would be caused by the creep phenomena. The small-scale mock-up test had been operated for about 50000 hours during 7 year. From the results, zirconium showed excellent corrosion resistance and no SCC was observed during these long-term operations. (authors)

Kato, Chiaki; Motooka, Takafumi; Yamamoto, Masahiro [Japan Atomic Energy Agency, Tokai-mura, Naka-gun, Ibaraki-ken 319-1195 (Japan)

2007-07-01

262

Corrosion testing of stainless steel-zirconium metal waste form.  

SciTech Connect

Stainless steel-zirconium (SS-Zr) alloys are being considered as waste forms for the disposition of metallic waste generated during the electrometallurgical treatment of spent nuclear fuel. The waste forms contain irradiated cladding hulls, components of the alloy fuel, noble metal fission products, and actinide elements. The baseline waste form is a stainless steel-15 wt% zirconium (SS-15Zr) alloy. This article presents microstructure and some of the corrosion studies being conducted on the waste form alloys. Electrochemical corrosion, immersion corrosion, and vapor hydration tests have been performed on various alloy compositions to evaluate corrosion behavior and resistance to selective leaching of simulated fission products. The SS-Zr waste forms are successful at the immobilization and retention of fission products and show potential for acceptance as high-level nuclear waste forms.

Abraham, D. P.

1998-12-14

263

Corrosion behavior of stainless steel-zirconium alloy waste forms.  

SciTech Connect

Stainless steel-zirconium (SS-Zr) alloys are being considered as waste forms for the disposal of metallic waste generated during the electrometallurgical treatment of spent nuclear fuel. The baseline waste form for spent fuels from the EBR-II reactor is a stainless steel-15 wt.% zirconium (SS-15Zr) alloy. This article briefly reviews the microstructure of various SS-Zr waste form alloys and presents results of immersion corrosion and electrochemical corrosion tests performed on these alloys. The electrochemical tests show that the corrosion behavior of SS-Zr alloys is comparable to those of other alloys being considered for the Yucca Mountain geologic repository. The immersion tests demonstrate that the SS-Zr alloys are resistant to selective leaching of fission product elements and, hence, suitable as candidates for high-level nuclear waste forms.

Abraham, D. P.

1999-01-13

264

Alumina zirconium ceramics synthesis by selective laser sintering/melting  

NASA Astrophysics Data System (ADS)

In the present paper, porous refractory ceramics synthesized by selective laser sintering/melting from a mixture of zirconium dioxide, aluminum and/or alumina powders are subjected to optical metallography and X-ray analysis to study their microstructure and phase composition depending on the laser processing parameters. It is shown that high-speed laser sintering in air yields ceramics with dense structure and a uniform distribution of the stabilizing phases. The obtained ceramic-matrix composites may be used as thermal and electrical insulators and wear resistant coating in solid oxide fuel cells, crucibles, heating elements, medical tools. The possibility to reinforce refractory ceramics by laser synthesis is shown on the example of tetragonal dioxide of zirconium with hardened micro-inclusion of Al 2O 3. By applying finely dispersed Y 2O 3 powder inclusions, the type of the ceramic structure is significantly changed.

Shishkovsky, I.; Yadroitsev, I.; Bertrand, Ph.; Smurov, I.

2007-12-01

265

Charge-optimized many-body (COMB) potential for zirconium  

NASA Astrophysics Data System (ADS)

An interatomic potential for zirconium is developed within the charge-optimized many-body (COMB) formalism. The potential correctly predicts the hexagonal close-packed (HCP) structure as the ground state with cohesive energy, lattice parameters, and elastic constants matching experiment well. The most stable interstitial position is the basal octahedral followed by basal split, in agreement with recent first principles calculations. Stacking fault energies within the prism and basal planes satisfactorily match first principles calculations. A tensile test using nanocrystalline zirconium exhibits both prismatic {1 0 1¯ 0}<1 1 2¯ 0> slip and pyramidal {1 1 2¯ 2}<1 1 2¯ 3¯> slip, showing the model is capable of reproducing the mechanical deformation modes observed in experiments.

Noordhoek, Mark J.; Liang, Tao; Lu, Zizhe; Shan, Tzu-Ray; Sinnott, Susan B.; Phillpot, Simon R.

2013-10-01

266

Immobilization of radioactive wastes: Leachability of glasses containing zirconium  

NASA Astrophysics Data System (ADS)

Sixteen borosilicate glasses containing up to 20% zirconium oxide and 10% simulated fission products or lanthanum oxide were prepared by fusion at 1150 to 1350°C. Their leaching rates in distilled water at 100°C as measured in a Soxhlet extractor varied from 0.9 to 10.9 × 10 -6 g/m 2· s . The results were analysed by multiple linear regression analysis. Some of the glasses studied may constitute a suitable matrix for the disposal of radioactive waste.

St-Pierre, J.; Tran, H. H.; Zikovsky, L.

1982-06-01

267

Fracture behavior of ?-zirconium phosphate-based epoxy nanocomposites  

Microsoft Academic Search

The fracture behaviors of ?-zirconium phosphate (?-ZrP) based epoxy nanocomposites, with and without core-shell rubber (CSR) toughening, were investigated. The state of exfoliation and dispersion of ?-ZrP nanofiller in epoxy were characterized using X-ray scattering and various microscopy tools. The level of enhancement in storage moduli of epoxy nanocomposite against neat epoxy is found to depend on the state of

H.-J. Sue; K. T. Gam; N. Bestaoui; A. Clearfield; M. Miyamoto; N. Miyatake

2004-01-01

268

Trivalent zirconium and hafnium ions in yttrium oxide ceramics  

NASA Astrophysics Data System (ADS)

An analysis of the electron spin resonance (ESR) spectrum of transparent ceramics composed of yttrium oxide with zirconium and hafnium additives has revealed the presence of signals (with similar parameters) from Zr3+ and Hf3+ ions, which have a similar electron configurations of the ground states: [Kr]4 d 1 and [Xe]5 d 1, respectively. It is shown that the pulsed cathodoluminescence spectra of these ions consist of two bands peaking at ? ? 818 and 900 nm.

Solomonov, V. I.; Spirina, A. V.; Konev, S. F.; Cholakh, S. O.

2014-05-01

269

Infiltration of zirconium diboride by ICVI in porous materials  

Microsoft Academic Search

This paper presents the results of an infiltration study, by ICVI, of zirconium diboride into three-dimensional porous preforms to make C\\/ZrB2 composites. An experimental design based on a model substrate shows the level and the sense of the influence of the parameters on the quality and kinetics of infiltration. Dilution of the reactants (BCl3, ZrCl4, H2) by helium improves infiltration

S. Berthon

1997-01-01

270

Pressureless Sintering of Zirconium Diboride: Particle Size and Additive Effects  

Microsoft Academic Search

Zirconium diboride (ZrB2) was densified by pressureless sinte- ring using o4-wt% boron carbide and\\/or carbon as sintering aids. As-received ZrB2 with an average particle size of B2 lm could be sintered to B100% density at 19001C using a combi- nation of boron carbide and carbon to react with and remove the surface oxide impurities. Even though particle size reduction in-

William G. Fahrenholtz; Gregory E. Hilmas; Shi C. Zhang; Sumin Zhu

2008-01-01

271

Pressureless sintering of carbon-coated zirconium diboride powders  

Microsoft Academic Search

Carbon-coated zirconium diboride powders were sintered to near theoretical density at temperatures as low as 1900°C without an external pressure. Relative density increased from ?70% for uncoated ZrB2 to >99% for ZrB2 coated with at least 1.0wt% carbon. Thermodynamic analysis indicated that carbon reacted with and removed oxide impurities (ZrO2 and B2O3) that were present on the particle surfaces, which

Sumin Zhu; William G. Fahrenholtz; Gregory E. Hilmas; Shi C. Zhang

2007-01-01

272

Zirconium diboride nanofiber generation via microwave arc heating  

Microsoft Academic Search

Ultrahigh temperature zirconium diboride nanofibers were produced by microwave arc heating using micron-sized raw powder. While microwave heating the ZrB2 powder, the development of local arcing led to rapid heating and solidification of the samples, along with the creation of nanofibers. The morphology of these high aspect ratio nanofibers was characterized using scanning electron microscopy and transmission electron microscopy. Energy

Tyson Baldridge; Mool C Gupta

2008-01-01

273

The abundances of zirconium and hafnium in the solar system  

Microsoft Academic Search

The concentrations of zirconium and hafnium have been determined in the Orgueil, Murchison, Allende, Bruderheim, and Alais meteorites by radiochemical neutron activation analysis. The mean Zr\\/Hf weight ratio in the first four of these meteorites is 31.3 (plus or minus 2.2), indicating no major fractionation of Zr from Hf. Alais contains anomalously high amounts of many refractory lithophile elements, including

R. Ganapathy; G. M. Papia; LAWRENCE GROSSMAN

1976-01-01

274

Powder metallurgical fabrication of zirconium matrix cermet nuclear fuels  

Microsoft Academic Search

Two powder metallurgical fabrication methods for a zirconium-based cermet nuclear dispersion fuel with oxide microspheres\\u000a have been demonstrated. A multi-pass, cold-drawing process is shown to have excellent capability to control the final matrix\\u000a density, though it requires several high-temperature anneals during fabrication to relieve strain hardening and increase matrix–particle\\u000a bonding. Severe oxide particle damage was observed in the cold-drawn fuel

Aaron R. Totemeier; Sean M. McDeavitt

2009-01-01

275

Oxidation characteristics of molybdenum-zirconium oxide cermets  

NASA Technical Reports Server (NTRS)

The oxidation of molybdenum is affected by the factors of temperature, the oxygen pressure in the oxidizing atmosphere, and the time of exposure. Studies of the oxidation characteristics of Mo show that the oxidation rate increases strongly when the temperature exceeds 600 C. Investigations of the behavior of cermets with various percentages of zirconium oxide are discussed, taking into account oxidation conditions at temperatures under and above the melting point of molybdenum trioxide.

Heitzinger, B.

1984-01-01

276

Microstructure and mechanical properties of proton irradiated zirconium carbide  

Microsoft Academic Search

Zirconium carbide is a candidate ceramic being considered for metal-carbide-base composite-type fuels, as well as for an alternative coating material for TRISO particle fuels. Ensuring adequate mechanical properties and dimensional stability in response to radiation is a key part in developing a practical ZrC-base fuel. The existing available radiation response data for ZrC is limited and insufficient. In the present

Yong Yang; Clayton A. Dickerson; Hannah Swoboda; Brandon Miller; Todd R. Allen

2008-01-01

277

Adsorption of formaldehyde by polyamine-intercalated ?-zirconium phosphate  

NASA Astrophysics Data System (ADS)

Gaseous formaldehyde adsorption mechanism of diethylenetriamine- and pentaethylenehexamine-intercalated ?-zirconium phosphate was demonstrated to be self oxidation-reduction of formaldehyde, that is, Cannizzaro reaction, in the interlayer space as evidenced by XRD and solid-state NMR. This fact suggests that these intercalation compounds can be used as a reaction field of self oxidation-reduction of formaldehyde, and also as adsorbents of formaldehyde, which causes sick-house syndrome.

Nakayama, H.; Hayashi, A.; Eguchi, T.; Nakamura, N.; Tsuhako, M.

2002-08-01

278

Oxygen in alloys of titanium with aluminum and zirconium  

Microsoft Academic Search

crease of the ultimate strength by 7-10 kg\\/mm 2, lowers the ductility. However, we found that binary alloys of titanium with aluminum retain fairly good ductility with 3-3.5% A1 when the oxygen content is 0.3-0.35%. In this case the alloy remains ductile, thermally stable, and is weldable and corrosion resistant. This work concerns the effect of zirconium in alloys of

I. I. Kornilov; T. A. Peradze; V. V. Vavilova; L. P. Fatkullina; O. S. Korobov

1973-01-01

279

Isothermal diffusion in uranium-plutonium-zirconium alloys  

NASA Astrophysics Data System (ADS)

Isothermal diffusion couple experiments were performed at 1023 K to investigate diffusion phenomena in body-centered cubic U?Pu?Zr alloys. The U?Pu?Zr alloys covered the uranium-rich corner of the ternary phase diagram with plutonium concentrations up to 27 at.% and zirconium concentrations up to 20 at.%. Ternary interdiffusion coefficients were calculated at the common composition between two couples with intersecting diffusion paths. The cross interdiffusion coefficient for zirconium ( D˜ZrPuU) is negative and has a magnitude twice that of the main coefficient ( D˜ZrZrU). In contrast, D˜PuZrU is negligible compared with D˜PuPuU, D˜PuPuU is an order of magnitude greater than D˜ZrZrU. Average effective interdiffusion coefficients were determined for all components over concentration ranges on the two sides of the Matano plane as well as for the entire diffusion zone of the couples. In general, these coefficients increase with increasing plutonium concentration and decrease with increasing zirconium concentration.

Petri, M. C.; Dayananda, M. A.

1997-01-01

280

Photodegradation of Paracetamol in Nitrate Solution  

SciTech Connect

The photodegradation of paracetamol in nitrate solution under simulated solar irradiation has been investigated. The degradation rates were compared by varying environmental parameters including concentrations of nitrate ion, humic substance and pH values. The quantifications of paracetamol were conducted by HPLC method. The results demonstrate that the photodegradation of paracetamol followed first-order kinetics. The photoproducts and intermediates of paracetamol in the presence of nitrate ions were identified by extensive GC-MS method. The photodegradation pathways involving. OH radicals as reactive species were proposed.

Meng Cui; Qu Ruijuan; Liang Jinyan; Yang Xi [State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210093 (China)

2010-11-24

281

Nitric oxide, oxidants, and protein tyrosine nitration  

PubMed Central

The occurrence of protein tyrosine nitration under disease conditions is now firmly established and represents a shift from the signal transducing physiological actions of •NO to oxidative and potentially pathogenic pathways. Tyrosine nitration is mediated by reactive nitrogen species such as peroxynitrite anion (ONOO–) and nitrogen dioxide (•NO2), formed as secondary products of •NO metabolism in the presence of oxidants including superoxide radicals (\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} \\begin{equation*}{\\mathrm{O}}_{2}^{{\\bullet}-}\\end{equation*}\\end{document}), hydrogen peroxide (H2O2), and transition metal centers. The precise interplay between •NO and oxidants and the identification of the proximal intermediate(s) responsible for nitration in vivo have been under controversy. Despite the capacity of peroxynitrite to mediate tyrosine nitration in vitro, its role on nitration in vivo has been questioned, and alternative pathways, including the nitrite/H2O2/hemeperoxidase and transition metal-dependent mechanisms, have been proposed. A balanced analysis of existing evidence indicates that (i) different nitration pathways can contribute to tyrosine nitration in vivo, and (ii) most, if not all, nitration pathways involve free radical biochemistry with carbonate radicals (\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} \\begin{equation*}{\\mathrm{CO}}_{3}^{{\\bullet}-}\\end{equation*}\\end{document}) and/or oxo–metal complexes oxidizing tyrosine to tyrosyl radical followed by the diffusion-controlled reaction with •NO2 to yield 3-nitrotyrosine. Although protein tyrosine nitration is a low-yield process in vivo, 3-nitrotyrosine has been revealed as a relevant biomarker of •NO-dependent oxidative stress; additionally, site-specific nitration focused on particular protein tyrosines may result in modification of function and promote a biological effect. Tissue distribution and quantitation of protein 3-nitrotyrosine, recognition of the predominant nitration pathways and individual identification of nitrated proteins in disease states open new avenues for the understanding and treatment of human pathologies.

Radi, Rafael

2004-01-01

282

Transport of nitrates through clay using electrokinetics  

SciTech Connect

In this paper, the results of laboratory experiments to investigate the feasibility of using electrokinetics to transport nitrates (a nutrient) through a low-permeability soil are presented. Tests were conducted using a kaolinite soil consolidated from a slurry under a vertical stress of 127 kPa. Sodium nitrate was introduced in a chamber in front of a graphite electrode that becomes the cathode in the electrokinetic process. A hydraulic head was used to reduce the osmotic pressures. The results of the tests reveal that, under laboratory conditions, nitrates can be transported through low-permeability soils using electrokinetics.

Budhu, M.; Rasmussen, W. [Univ. of Arizona, Tucson, AZ (United States); Rutherford, M.; Sills, G. [Univ. of Oxford (United Kingdom)

1997-12-01

283

Growth of thin zirconium and zirconium oxides films on the n-GaN(0 0 0 1) surface studied by XPS and LEED  

NASA Astrophysics Data System (ADS)

This work presents the result of the growth of thin zirconium films on the GaN(0 0 0 1) surface under various conditions. In experiment were used the X-ray photoelectron spectroscopy (XPS) and low-energy electron diffraction (LEED) techniques, which allowed to investigate the chemical composition, bonding environment and surface reconstruction. It is shown that zirconium forms ZrN, ZrNxOy, ZrOx and ZrO2 compounds, depending on the selected experimental conditions: the pressure and annealing temperature. Such a varied zirconium growth behaviour is explained by the diffusion of oxygen and nitrogen in the created interface region.

Idczak, K.; Mazur, P.; Zuber, S.; Markowski, L.; Ski?cim, M.; Bili?ska, S.

2014-06-01

284

Phase diagram of ammonium nitrate  

SciTech Connect

Ammonium Nitrate (AN) is a fertilizer, yet becomes an explosive upon a small addition of chemical impurities. The origin of enhanced chemical sensitivity in impure AN (or AN mixtures) is not well understood, posing significant safety issues in using AN even today. To remedy the situation, we have carried out an extensive study to investigate the phase stability of AN and its mixtures with hexane (ANFO–AN mixed with fuel oil) and Aluminum (Ammonal) at high pressures and temperatures, using diamond anvil cells (DAC) and micro-Raman spectroscopy. The results indicate that pure AN decomposes to N{sub 2}, N{sub 2}O, and H{sub 2}O at the onset of the melt, whereas the mixtures, ANFO and Ammonal, decompose at substantially lower temperatures. The present results also confirm the recently proposed phase IV-IV{sup ?} transition above 17 GPa and provide new constraints for the melting and phase diagram of AN to 40 GPa and 400°C.

Dunuwille, Mihindra; Yoo, Choong-Shik, E-mail: csyoo@wsu.edu [Department of Chemistry and Institute for Shock Physics, Washington State University, Pullman, Washington 99164 (United States)] [Department of Chemistry and Institute for Shock Physics, Washington State University, Pullman, Washington 99164 (United States)

2013-12-07

285

Nitrate removal and denitrification affected by soil characteristics in nitrate treatment wetlands  

Microsoft Academic Search

Several small-scale surface flow constructed wetlands unplanted and planted (monoculture) with various macrophytes (Phragmites australis, Typha orientalis, Pennisetum purpureum, Ipomoea aquatica, and Pistia stratiotes) were established to continuously receive nitrate-contaminated groundwater. Soil characteristics and their effects on nitrate removal and soil denitrification were investigated. The results showed that planted wetland cells exhibited significantly higher (P < 0.05) nitrate removal efficiencies

Ying-Feng Lin; Shuh-Ren Jing; Der-Yuan Lee; Yih-Feng Chang; Kai-Chung Shih

2007-01-01

286

?-Pinene Nitrates: Synthesis, Identification and Yields  

NASA Astrophysics Data System (ADS)

?-Pinene emitted by vegetation is the dominant monoterpene emitted in Earth’s atmosphere with estimated annual global emissions of ~50 Tg yr-1. Its oxidation products and reaction mechanism is an important consideration in tropospheric chemistry. The major oxidation pathway of ?-pinene is reaction with OH in the presence of NO which can form either a-pinene nitrates or convert NO to NO2 which can photolyze to form ozone. To date, there is little experimental knowledge of the relative importance of the individual a-pinene nitrate isomers, each of which has a different fate and reactivity. In this work, we synthesized 4 a-pinene multifunctional nitrates through four different routes and have identified the 4 individual isomers in a-pinene/NOx chamber experiments and determined their individual production yields, and the total RONO2 yield, and calculated the relative branching ratios of nitrate precursor peroxy radical (RO2).

Ma, S.; Shepson, P. B.; Rindelaub, J.; Nault, B.

2010-12-01

287

Thermal Characteristics of Concentrated Hydroxylammonium Nitrate Solutions.  

National Technical Information Service (NTIS)

The thermal response of concentrated hydroxylammonium nitrate solutions has been studied where solutions have been brought to boiling, with only a small degree of decomposition being noted over protracted time periods. Boiling points were related to molar...

R. A. Sasse

1988-01-01

288

Analysis of Hydroxylammonium Nitrate Based Liquid Propellants.  

National Technical Information Service (NTIS)

Chemical analysis of hydroxlammonium nitrate (HAN) based liquid propellants have matured over the past twenty years, and various techniques have been offered to meet particular requirements at particular times. This has resulted in a plethora of technolog...

R. Sasse

1990-01-01

289

The influence of ammonium on nitrate reduction in wheat seedlings  

Microsoft Academic Search

Ammonium markedly inhibited nitrate absorption by nitrogenstarved wheat seedlings but did not decrease the proportion of absorbed nitrate that was reduced. Seedlings high in nitrate (absorbed prior to the experimental periods) reduced similar amounts of this nitrate regardless of whether or not ammonium was present and being absorbed during the period of measurement. Ammonium or products of ammonium assimilation did

P. L. Minotti; Doris Craig Williams; W. A. Jackson

1969-01-01

290

The Arabidopsis ATNRT2.7 Nitrate Transporter Controls Nitrate Content in Seeds[W  

PubMed Central

In higher plants, nitrate is taken up by root cells where Arabidopsis thaliana NITRATE TRANSPORTER2.1 (ATNRT2.1) chiefly acts as the high-affinity nitrate uptake system. Nitrate taken up by the roots can then be translocated from the root to the leaves and the seeds. In this work, the function of the ATNRT2.7 gene, one of the seven members of the NRT2 family in Arabidopsis, was investigated. High expression of the gene was detected in reproductive organs and peaked in dry seeds. ?-Glucuronidase or green fluorescent protein reporter gene expression driven by the ATNRT2.7 promoter confirmed this organ specificity. We assessed the capacity of ATNRT2.7 to transport nitrate in Xenopus laevis oocytes or when it is expressed ectopically in mutant plants deficient in nitrate transport. We measured the impact of an ATNRT2.7 mutation and found no difference from the wild type during vegetative development. By contrast, seed nitrate content was affected by overexpression of ATNRT2.7 or a mutation in the gene. Finally, we showed that this nitrate transporter protein was localized to the vacuolar membrane. Our results demonstrate that ATNRT2.7 plays a specific role in nitrate accumulation in the seed.

Chopin, Franck; Orsel, Mathilde; Dorbe, Marie-France; Chardon, Fabien; Truong, Hoai-Nam; Miller, Anthony J.; Krapp, Anne; Daniel-Vedele, Francoise

2007-01-01

291

Nitrate inhibition of legume nodule growth and activity. II. Short term studies with high nitrate supply  

SciTech Connect

Soybean plants (Glycine max (L.) Merr) were grown in sand culture with 2 millimolar nitrate for 37 days and then supplied with 15 millimolar nitrate for 7 days. Control plants received 2 millimolar nitrate and 13 millimolar chloride and, after the 7-day treatment period, all plants were supplied with nil nitrate. The temporary treatment with high nitrate inhibited nitrogenase (acetylene reduction) activity by 80% whether or not Rhizobium japonicum bacteroids had nitrate reductase (NR) activity. The pattern of nitrite accumulation in nodules formed by NR/sup +/ rhizobia was inversely related to the decrease and recovery of nitrogenase activity. However, nitrite concentration in nodules formed by NR/sup -/ rhizobia appeared to be too low to explain the inhibition of nitrogenase. Nodules on plants treated with 15 millimolar nitrate contained higher concentrations of amino N and, especially, ureide N than control nodules and, after withdrawal of nitrate, reduced N content of treated and control nodules returned to similar levels. The accumulation of N/sub 2/ fixation products in nodules in response to high nitrate treatment was observed with three R. japonicum strains, two NR/sup +/ and one NR/sup -/.

Streeter, J.G.

1985-02-01

292

Nitrate pollution of groundwater in northern China  

Microsoft Academic Search

Since the 1980s, nitrogen fertiliser consumption in China has increased substantially. High nitrogen application rates may increase the potential groundwater N-pollution. These effects were investigated in 14 cities and counties in northern China. The Merckoquant-nitrate-test strip was used to measure the nitrate concentration in water. Information on well depth, groundwater level, crop rotation, yield and fertiliser application was obtained.The results

W. L. Zhang; Z. X. Tian; N. Zhang; X. Q. Li

1996-01-01

293

The UK Nitrate Time Bomb (Invited)  

NASA Astrophysics Data System (ADS)

The developed world has benefitted enormously from the intensification of agriculture and the increased availability and use of synthetic fertilizers during the last century. However there has also been unintended adverse impact on the natural environment (water and ecosystems) with nitrate the most significant cause of water pollution and ecosystem damage . Many countries have introduced controls on nitrate, e.g. the European Union's Water Framework and Nitrate Directives, but despite this are continuing to see a serious decline in water quality. The purpose of our research is to investigate and quantify the importance of the unsaturated (vadose) zone pathway and groundwater in contributing to the decline. Understanding nutrient behaviour in the sub-surface environment and, in particular, the time lag between action and improvement is critical to effective management and remediation of nutrient pollution. A readily-transferable process-based model has been used to predict temporal loading of nitrate at the water table across the UK. A time-varying nitrate input function has been developed based on nitrate usage since 1925. Depth to the water table has been calculated from groundwater levels based on regional-scale observations in-filled by interpolated river base levels and vertical unsaturated zone velocities estimated from hydrogeological properties and mapping. The model has been validated using the results of more than 300 unsaturated zone nitrate profiles. Results show that for about 60% of the Chalk - the principal aquifer in the UK - peak nitrate input has yet to reach the water table and concentrations will continue to rise over the next 60 years. The implications are hugely significant especially where environmental objectives must be achieved in much shorter timescales. Current environmental and regulatory management strategies rarely take lag times into account and as a result will be poorly informed, leading to inappropriate controls and conflicts between policy makers, environmentalists and industry.

Ward, R.; Wang, L.; Stuart, M.; Bloomfield, J.; Gooddy, D.; Lewis, M.; McKenzie, A.

2013-12-01

294

Factors Responsible for Nitrate Accumulation: A Review  

Microsoft Academic Search

Leafy vegetables occupy a very important place in the human diet, but unfortunately, constitute a group of foods, which contributes\\u000a maximally to nitrate consumption by living beings. Under excessive application of nitrogen fertilizer, these vegetables can\\u000a accumulate high levels of nitrate and, on being consumed by living beings, pose serious health hazards. Therefore, efforts\\u000a are warranted to minimize the accumulation

Anjana; Shahid Umar; Muhammad Iqbal

295

Molecular evolution of nitrate reductase genes  

Microsoft Academic Search

To understand the evolutionary mechanisms and relationships of nitrate reductases (NRs), the nucleotide sequences encoding\\u000a 19 nitrate reductase (NR) genes from 16 species of fungi, algae, and higher plants were analyzed. The NR genes examined show\\u000a substantial sequence similarity, particularly within functional domains, and large variations in GC content at the third codon\\u000a position and intron number. The intron positions

Jizhong Zhou; Andris Kleinhofs

1996-01-01

296

Synthesis of a new energetic nitrate ester  

SciTech Connect

Nitrate esters have been known as useful energetic materials since the discovery of nitroglycerin by Ascanio Sobrero in 1846. The development of methods to increase the safety and utility of nitroglycerin by Alfred Nobel led to the revolutionary improvement in the utility of nitroglycerin in explosive applications in the form of dynamite. Since then, many nitrate esters have been prepared and incorporated into military applications such as double-based propellants, detonators and as energetic plasticizers. Nitrate esters have also been shown to have vasodilatory effects in humans and thus have been studied and used for treatments of ailments such as angina. The mechanism of the biological response towards nitrate esters has been elucidated recently. Interestingly, many of the nitrate esters used for military purposes are liquids (ethylene glycol dinitrate, propylene glycol dinitrate, etc). Pentaerythritol tetranitrate (PETN) is one of the only solid nitrate esters, besides nitrocellulose, that is used in any application. Unfortunately, PETN melting point is above 100 {sup o}C, and thus must be pressed as a solid for detonator applications. A more practical material would be a melt-castable explosive, for potential simplification of manufacturing processes. Herein we describe the synthesis of a new energetic nitrate ester (1) that is a solid at ambient temperatures, has a melting point of 85-86 {sup o}C and has the highest density of any known nitrate ester composed only of carbon, hydrogen, nitrogen and oxygen. We also describe the chemical, thermal and sensitivity properties of 1 as well as some preliminary explosive performance data.

Chavez, David E [Los Alamos National Laboratory

2008-01-01

297

Characterization of Atmospheric Organic Nitrates in Particles  

NASA Astrophysics Data System (ADS)

Aerosols in the atmosphere significantly affect climate, human health and visibility. Knowledge of aerosol composition is necessary to understand and then predict the specific impacts of aerosols in the atmosphere. It is known that organic nitrates are present in particles, but there is limited knowledge of the individual compounds and quantity. This is in part due to the lack of a wide variety of proven analytical techniques for particulate organic nitrates. In this study, several known organic nitrates, as well as those present in complex mixtures formed from oxidation of "Ñ-pinene, were studied using a variety of techniques. These include Fourier Transform infrared spectroscopy (FTIR) of samples collected by impaction on ZnSe discs. Samples were also collected on quartz fiber filters and the extracts analyzed by electrospray mass spectrometry (ESI- MS), atmospheric pressure chemical ionization mass spectrometry (APCI-MS), HPLC-UV, LC-MS and GC-MS. In addition, real-time analysis was provided by SPLAT-II and aerosol mass spectrometry (AMS). FTIR analysis of particles collected on ZnSe discs provides information on the ratio of organic nitrate to total organic content, while the analysis of filter extracts allows identification of specific organic nitrates. These are compared to the particle mass spectrometry data and the implications for detecting and measuring particulate organic nitrate in air is discussed.

Bruns, E. A.; Alexander, M. L.; Perraud, V.; Yu, Y.; Ezell, M.; Johnson, S. N.; Zellenyuk, A.; Imre, D.; Finlayson-Pitts, B. J.

2008-12-01

298

Stimulating nitrate removal processes of restored wetlands.  

PubMed

The environmental and health effects caused by nitrate contamination of aquatic systems are a serious problem throughout the world. A strategy proposed to address nitrate pollution is the restoration of wetlands. However, although natural wetlands often remove nitrate via high rates of denitrification, wetlands restored for water quality functions often fall below expectations. This may be in part because key drivers for denitrification, in particular soil carbon, are slow to develop in restored wetlands. We added organic soil amendments that range along a gradient of carbon lability to four newly restored wetlands in western New York to investigate the effect of carbon additions on denitrification and other processes of the nitrogen cycle. Soil carbon increased by 12.67-63.30% with the use of soil amendments (p ? 0.0001). Soil nitrate, the carbon to nitrogen ratio, and microbial biomass nitrogen were the most significant predictors of denitrification potential. Denitrification potential, potential net nitrogen nitrification and mineralization, and soil nitrate and ammonium, were highest in topsoil-amended plots, with increases in denitrification potential of 161.27% over control plots. While amendment with topsoil more than doubled several key nitrogen cycling processes, more research is required to determine what type and level of amendment application are most effective for stimulating removal of exogenous nitrate and meeting functional goals within an acceptable time frame. PMID:24915604

Ballantine, Kate A; Groffman, Peter M; Lehmann, Johannes; Schneider, Rebecca L

2014-07-01

299

Protein tyrosine nitration in the cell cycle  

SciTech Connect

Highlights: {yields} Enrichment of 3-nitrotyrosine containing proteins from cells synchronized in different phases of the cell cycle. {yields} Identification of 76 tyrosine nitrated proteins that change expression during the cell cycle. {yields} Nineteen identified proteins were previously described as regulators of cell proliferation. -- Abstract: Nitration of tyrosine residues in proteins is associated with cell response to oxidative/nitrosative stress. Tyrosine nitration is relatively low abundant post-translational modification that may affect protein functions. Little is known about the extent of protein tyrosine nitration in cells during progression through the cell cycle. Here we report identification of proteins enriched for tyrosine nitration in cells synchronized in G0/G1, S or G2/M phases of the cell cycle. We identified 27 proteins in cells synchronized in G0/G1 phase, 37 proteins in S phase synchronized cells, and 12 proteins related to G2/M phase. Nineteen of the identified proteins were previously described as regulators of cell proliferation. Thus, our data indicate which tyrosine nitrated proteins may affect regulation of the cell cycle.

Jia, Min, E-mail: min.jia@ki.se [Department of Oncology-Pathology, Karolinska Institutet, Stockholm (Sweden)] [Department of Oncology-Pathology, Karolinska Institutet, Stockholm (Sweden); Mateoiu, Claudia; Souchelnytskyi, Serhiy [Department of Oncology-Pathology, Karolinska Institutet, Stockholm (Sweden)] [Department of Oncology-Pathology, Karolinska Institutet, Stockholm (Sweden)

2011-09-23

300

Fabrication and formation of bioactive anodic zirconium oxide nanotubes containing presynthesized hydroxyapatite via alternative immersion method  

Microsoft Academic Search

Hydroxyapatite (HA) coating has been widely applied on metallic biomedical implants to enhance their biocompatibility. It has been reported that HA coating can be formed on annealed zirconium with anodic zirconium oxide nanotubular arrays after immersion in simulated biological fluid (SBF) for about 14days. In the present study, we apply an alternative immersion method (AIM) to form presynthesized HA on

Lu-Ning Wang; Jing-Li Luo

2011-01-01

301

Wetting and infiltration of zirconium diboride by copper and copper\\/boron alloys  

Microsoft Academic Search

Purpose – This paper investigates wetting and infiltration of zirconium diboride by copper and copper\\/boron alloys in order to more effectively create electrodes for electrical discharge machining. Design\\/methodology\\/approach – A high temperature furnace outfitted with a video recording system was utilized to observe wetting angles between molten copper alloys and zirconium diboride at various temperatures. A parallel, investigation of the

Brent E. Stucker; Walter L. Bradley

2006-01-01

302

Lithium aluminate/zirconium material useful in the production of tritium  

DOEpatents

A composition is described useful in the production of tritium in a nuclear eactor. Lithium aluminate particles are dispersed in a matrix of zirconium. Tritium produced by the reactor of neutrons with the lithium are absorbed by the zirconium, thereby decreasing gas pressure within capsules carrying the material.

Cawley, William E. (Richland, WA); Trapp, Turner J. (Richland, WA)

1984-10-09

303

Lithium aluminate/zirconium material useful in the production of tritium  

DOEpatents

A composition is described useful in the production of tritium in a nuclear reactor. Lithium aluminate particles are dispersed in a matrix of zirconium. Tritium produced by the reactor of neutrons with the lithium are absorbed by the zirconium, thereby decreasing gas pressure within capsules carrying the material.

Cawley, W.E.; Trapp, T.J.

1984-10-09

304

DETERMINATION OF ZIRCONIUM AND HAFNIUM WITH XYLENOL ORANGE AND METHYLTHYMOL BLUE  

Microsoft Academic Search

Both Xylenol Orange and Methylthymol Blue are highly selective and ; sensitive reagents for zirconium and hafnium forming intensely red complexes in ; an acidic medium. The factors affecting the color formation were studied. The ; properties of the complex were determined and compared. In general, zirconium ; forms a more stable complex with the two dyes than hafnium, and

K. L. Cheng

1963-01-01

305

Zirconium Distribution in the System HNO sub 3 -H sub 2 O-TBP-Diluent.  

National Technical Information Service (NTIS)

The extraction behaviour of zirconium in TBP/diluent-HNO sub 3 -H sub 2 O systems is studied in order to increase the uranium decontamination factor by adjusting the extraction conditions so that zirconium extraction is kept at a minimum. Equilibrium diag...

J. Shu, B. F. Araujo

1984-01-01

306

Measurement of impurity diffusion into the liner of a zirconium-lined zircaloy-2 tube  

NASA Astrophysics Data System (ADS)

A method using Auger Electron Spectroscopy (AES) techniques has been developed for measuring the distribution of oxygen and tin across the zirconium liner of zirconium-lined/Zircaloy-2 tubing. This is the first time that an oxygen profile has been successfully measured across the zirconium liner in pilgered tubing. The method is accurate for the determination of oxygen in the concentration range of 100 to 1200 ppm. Measurements were performed on an as-beta-quenched zirconium-lined intermediate size tube sample. The data show negligible tin penetration into the zirconium liner. Oxygen penetration to a depth of 15 to 45 ?m into the zirconium liner was measured at the zirconium liner/Zircaloy-2 interface. Oxygen penetration to a depth of about 20 ?m into the zirconium liner occurred at the inside diameter surface. A methodology for calculating the oxygen diffusion concentration profile was established. The diffusion penetration width geometrically decreases due to tube wall reduction and increases by thermal annealing. When the tubing is processed from the beta-quenched to the final size the diffusion width decreases. Hence, the effect of decreasing wall thickness on the diffusion width is greater than that due to thermal annealing. The calculation methodology could be used to predict the tin and oxygen concentration profiles at the bondline of tubing fabricated by alternate processing sequences.

Foster, John P.; Byers, W. A.

1990-05-01

307

Zirconium-base alloy structural component for nuclear reactor and method  

US Patent & Trademark Office Database

A small amount of lanthanum and praseodymium will substantially improve the slow strain rate ductility of certain zirconium-base alloys and these new alloys and certain other zirconium-base alloys in the irradiated condition can under certain circumstances have surprising load-carrying capacity and service life. Such other alloys contain yttrium or calcium instead of lanthanum or praseodymium.

1980-04-08

308

Vapor transport of zirconium and silicon during heat-treatment of Zircaloy in silica  

Microsoft Academic Search

When pieces of Zircaloy are heated above 600°C in sealed silica capsules, silicon is deposited on the Zircaloy surface as zirconium silicides and zirconium is deposited on the silica in two forms: as an oxide layer in the high temperature region and as a metallic mirror on lower temperature surfaces. Samples of Zircaloy were heated in silica capsules under various

D. R. Knittel; D. Cubicciotti

1980-01-01

309

Preparation of microspherical ?-zirconium phosphate catalysts for conversion of fatty acid methyl esters to monoethanolamides  

Microsoft Academic Search

The performance of solid catalysts and catalyst supports is generally believed to be dependent on their morphology, surface area, and architecture. In order to fully exploit their attractive properties in actual practical applications, layered zirconium phosphate materials should be fabricated into macroscopic form. Here, we report the fabrication of microscopic spheres of ?-zirconium phosphate (?-ZrP) by a spray-drying process. The

Fazhi Zhang; Yaru Xie; Wei Lu; Xiaoying Wang; Sailong Xu; Xiaodong Lei

2010-01-01

310

Metabolism of nitrate- and ammonium-nitrogen absorbed from ammonium nitrate and ammonium sulfate in the tobacco plant  

Microsoft Academic Search

In water culture experiments with tobacco plants, ammonium nitrate has been generally used as a nitrogen source. In a comparison among various nitrogen sources for water cultured tobacco, better growth has been obtained with ammonium nitrate than with sodium nitrate and ammonium sulfate (1). It has been shown that both ammonium- and nitrate-nitrogen are simultaneously absorbed by the tobacco plant

Daisuke Yoshida

1966-01-01

311

Resistance a la corrosion du zirconium: mecanismes generaux, comportement en milieu nitrique. (Corrosion resistance of zirconium: general mechanisms, behaviour in nitric acid).  

National Technical Information Service (NTIS)

Corrosion resistance of zirconium results from the strong affinity of this metal for oxygen; as a result a thin protective oxide film is spontaneously formed in air or aqueous media, its thickness and properties depending on the physicochemical conditions...

G. Pinard Legry

1990-01-01

312

A simple spectrophotometric method for determination of zirconium or hafnium in selected molybdenum-base alloys  

NASA Technical Reports Server (NTRS)

A simple analytical procedure is described for accurately and precisely determining the zirconium or hafnium content of molybdenum-base alloys. The procedure is based on the reaction of the reagent Arsenazo III with zirconium or hafnium in strong hydrochloric acid solution. The colored complexes of zirconium or hafnium are formed in the presence of molybdenum. Titanium or rhenium in the alloy have no adverse effect on the zirconium or hafnium complex at the following levels in the selected aliquot: Mo, 10 mg; Re, 10 mg; Ti, 1 mg. The spectrophotometric measurement of the zirconium or hafnium complex is accomplished without prior separation with a relative standard deviation of 1.3 to 2.7 percent.

Dupraw, W. A.

1972-01-01

313

Direct determination of zirconium in alloys by normal and derivative spectrophotometry  

SciTech Connect

This paper discusses the possibility of determining zirconium at a pH 2.8-3.2 with a sensitivity equal to that obtainable in HC1 when using electron spectra and a sensitivity equal to that obtainable in the reaction of zirconium with Arsenazo III in 9-10 M HC1 when using higher-order derivative spectra. This is achieved by adding sodium molybdate ions to the analyzed solution, which also allowed for the determination of zirconium in oxidizing media. The study establishes the formation of a multimetal complex from zirconium ions, arsenazo III, and sodium molybdate. Based on this complex, a method has been developed for the direct determination of zirconium in alloys which distinguishes itself from the known methods by a significantly simpler analytical procedure.

Spitsyn, P.K.

1985-11-01

314

Field assessment of the dynamics of particulate nitrate vaporization using differential TEOM ® and automated nitrate monitors  

NASA Astrophysics Data System (ADS)

In this study, we report a comparison of the results from the differential tapered element oscillating microbalance (TEOM) and a semi-continuous nitrate monitor in an attempt to obtain insights into the dynamics of volatilization from the heated TEOM filter. Measurements were conducted in Claremont, California, a city downwind of Los Angeles and a region of high nitrate concentrations. Field results are compared with that obtained in the laboratory for sampling of pure ammonium nitrate aerosol, and with the vaporization losses predicted by theory. The primary hypothesis that we are testing is that the nitric acid and ammonia gas volatilization from particle-bound ammonium nitrate loaded on the TEOM's fiber filter occurs over time scales that are longer than the 5-min cycle time for the system. This is important to the use of the Differential TEOM, which utilizes the vaporization measured during alternate 5-min periods as a reference baseline value for its particle mass measurements. Our experiments showed that under ambient conditions, the mass lost from the Differential TEOM tracks well the ambient particulate nitrate concentration. The saturation ratio for nitrate vapor immediately downstream of the filter, calculated at the filter temperature assuming all volatilized mass is ammonium nitrate, ranged from 0.05 to 0.2. By comparison, for laboratory collection of ammonium nitrate aerosol the vaporization reached a maximum value corresponding to a saturation of nitrate vapor downstream of the heated filter. This difference is due to the relatively higher particle concentrations used for the laboratory experiments. For the ambient measurements, the particulate nitrate concentrations were consistently lower than the equilibrium vapor concentration at the TEOM filter temperature. In both cases, the nitrate vaporization is driven by the temperature of the TEOM filter and independent of the pressure drop across the filter.

Hering, Susanne; Fine, Philip M.; Sioutas, Constantinos; Jaques, Peter A.; Ambs, Jeffrey L.; Hogrefe, Olga; Demerjian, Kenneth L.

315

Nitrate in groundwater in the United States  

NASA Astrophysics Data System (ADS)

An assessment of nitrate concentrations in groundwater in the United States (US) indicates that concentrations are highest in shallow, oxic groundwater beneath areas with high nitrogen inputs. During 1991-2003, 5,101 wells were sampled in 51 study areas throughout the US as part of the USGS National Water-Quality Assessment program. Well locations for individual 30-well networks were selected for sampling using a computerized, stratified, random site-selection procedure to minimize spatial bias. These well networks reflect the existing used resource in major aquifers represented by domestic wells (major aquifer studies), and recently recharged groundwater beneath dominant land-surface activities (land-use studies). Nitrate concentrations in groundwater were compared with nationally-available variables such as nonpoint-source nitrogen inputs, soils, water chemistry, and other aquifer and well construction characteristics to predict the conditions most vulnerable to high nitrate concentrations. Nitrate was detected at concentrations above background of 1.0 mg/L (as N) in 50% of the wells sampled. Shallow groundwater beneath agricultural land had the highest median concentration of nitrate (3.1 mg/L). Median nitrate in shallow groundwater beneath urban land (1.4 mg/L) was lower than beneath agricultural land, but was higher than the median in major aquifers (0.56 mg/L). Although most wells sampled in the shallow land-use studies were not used for drinking water, concentrations exceeded the US EPA drinking-water standard (MCL) of 10 mg/L in 20% of wells in the agricultural land-use setting. Concentrations exceeded the MCL in only 3% of wells in the urban land-use setting, and 4% of wells in major aquifers. Classification and regression tree analysis was used to identify the relative importance of nitrogen inputs, water chemistry, and physical aquifer properties on nitrate concentrations in groundwater. Factors ranked by reduction in sum of squares indicate that dissolved iron concentrations explained most of the variation in groundwater nitrate concentration, followed by manganese, calcium, farm fertilizer, percent well-drained soils, dissolved oxygen, and other chemical and physical factors. The high rankings of iron, manganese, and farm fertilizer indicate that nitrate concentrations in groundwater are most significantly affected by redox conditions and nonpoint-source nitrogen inputs. The other water-quality indicators and physical variables have a secondary influence on nitrate concentrations.

Burow, K. R.; Nolan, B. T.; Rupert, M. G.; Dubrovsky, N. M.

2009-12-01

316

Quantification of nitrotyrosine in nitrated proteins  

PubMed Central

For kinetic studies of protein nitration reactions, we have developed a method for the quantification of nitrotyrosine residues in protein molecules by liquid chromatography coupled to a diode array detector of ultraviolet-visible absorption. Nitrated bovine serum albumin (BSA) and nitrated ovalbumin (OVA) were synthesized and used as standards for the determination of the protein nitration degree (ND), which is defined as the average number of nitrotyrosine residues divided by the total number of tyrosine residues in a protein molecule. The obtained calibration curves of the ratio of chromatographic peak areas of absorbance at 357 and at 280 nm vs. nitration degree are nearly the same for BSA and OVA (relative deviations <5%). They are near-linear at low ND (< 0.1) and can be described by a second-order polynomial fit up to \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {\\hbox{ND}} = 0.5\\left( {{R^2} > 0.99} \\right) $$\\end{document}. A change of chromatographic column led to changes in absolute peak areas but not in the peak area ratios and related calibration functions, which confirms the robustness of the analytical method. First results of laboratory experiments confirm that the method is applicable for the investigation of the reaction kinetics of protein nitration. The main advantage over alternative methods is that nitration degrees can be efficiently determined without hydrolysis or digestion of the investigated protein molecules.

Zhang, Yingyi; Poschl, Ulrich

2010-01-01

317

Nitrate in aquifers beneath agricultural systems  

USGS Publications Warehouse

Research from several regions of the world provides spatially anecdotal evidence to hypothesize which hydrologic and agricultural factors contribute to groundwater vulnerability to nitrate contamination. Analysis of nationally consistent measurements from the U.S. Geological Survey's NAWQA program confirms these hypotheses for a substantial range of agricultural systems. Shallow unconfined aquifers are most susceptible to nitrate contamination associated with agricultural systems. Alluvial and other unconsolidated aquifers are the most vulnerable and also shallow carbonate aquifers that provide a substantial but smaller contamination risk. Where any of these aquifers are overlain by permeable soils the risk of contamination is larger. Irrigated systems can compound this vulnerability by increasing leaching facilitated by additional recharge and additional nutrient applications. The system of corn, soybean, and hogs produced significantly larger concentrations of groundwater nitrate than all other agricultural systems because this system imports the largest amount of N-fertilizer per unit production area. Mean nitrate under dairy, poultry, horticulture, and cattle and grains systems were similar. If trends in the relation between increased fertilizer use and groundwater nitrate in the United States are repeated in other regions of the world, Asia may experience increasing problems because of recent increases in fertilizer use. Groundwater monitoring in Western and Eastern Europe as well as Russia over the next decade may provide data to determine if the trend in increased nitrate contamination can be reversed. If the concentrated livestock trend in the United States is global, it may be accompanied by increasing nitrogen contamination in groundwater. Concentrated livestock provide both point sources in the confinement area and intense non-point sources as fields close to facilities are used for manure disposal. Regions where irrigated cropland is expanding, such as in Asia, may experience the greatest impact of this practice on groundwater nitrate. ?? USDA 2007.

Burkart, M. R.; Stoner, J. D.

2007-01-01

318

Observations of Alkyl Nitrates during ARCTAS: Investigation of the low NOx Chemistry of Isoprene Nitrates  

NASA Astrophysics Data System (ADS)

During numerous ground and airborne experiments alkyl and multifunctional nitrates, measured by Thermal Dissociation-Laser Induced Fluorescence, have been shown to represent a significant fraction of oxidized nitrogen. It is postulated that a large fraction of these nitrates, particularly in forested environments, are isoprene-derived nitrates. The formation of these nitrates is important in terminating photochemical ozone production. However, it is still highly uncertain if these nitrates serve as a permanent termination step or only as a temporary sink that upon further oxidation, releases NO2 back into the atmosphere. The summer portion of the NASA ARCTAS experiment allows us to investigate the role of alkyl nitrates in photochemical ozone production in a new regime: the low NOx of the summer boreal forest. This data set also represents the first time that vertical profiles of the isoprene oxidation products methyl vinyl ketone and methacrolein were obtained along with total alkyl nitrates. We use these measurements to investigate and constrain the low NOx chemistry of isoprene nitrates. We compare these measurements to past airborne and laboratory studies.

Browne, E. C.; Cohen, R. C.; Wooldridge, P. J.; Min, K.; Apel, E. C.; Blake, D. R.; Brune, W. H.; Fried, A.; Ren, X.; Weinheimer, A. J.; Wisthaler, A.; Team, A. S.

2009-12-01

319

COMPARATIVE KINETIC STUDIES OF NITRATE-LIMITED GROWTH AND NITRATE UPTAKE IN PHYTOPLANKTON IN CONTINUOUS CULTURE  

EPA Science Inventory

A comparative kinetic study of nitrate-limited growth and nitrate uptake was carried out in chemostat cultures of Ankistrodesmus falcatus, Asterionella formosa, Fragilaria crotonensis. In each species growth rate (microgram) was related to total cell nitrogen or cell quota (q) by...

320

Field assessment of the dynamics of particulate nitrate vaporization using differential TEOM ® and automated nitrate monitors  

Microsoft Academic Search

In this study, we report a comparison of the results from the differential tapered element oscillating microbalance (TEOM) and a semi-continuous nitrate monitor in an attempt to obtain insights into the dynamics of volatilization from the heated TEOM filter. Measurements were conducted in Claremont, California, a city downwind of Los Angeles and a region of high nitrate concentrations. Field results

Susanne Hering; Philip M. Fine; Constantinos Sioutas; Peter A. Jaques; Jeffrey L. Ambs; Olga Hogrefe; Kenneth L. Demerjian

2004-01-01

321

Infrared Spectra and Intermolecular Potentials of Matrix Isolated Methyl Nitrate and Methyl-d3-Nitrate.  

National Technical Information Service (NTIS)

The infrared spectra of protonated and deuterated methyl nitrate isolated in a nitrogen matrix have been recorded from 4000 to 250/cm. Peaks have been assigned to monomers, pairs, and higher-ordered species by varying the concentration of methyl nitrate i...

J. A. Lannon W. G. Thomas F. D. Verderame L. E. Harris E. A. Lucia

1973-01-01

322

Effect of nitrate exposure history on the oxygen\\/nitrate diauxic growth of pseudomonas denitrificans  

Microsoft Academic Search

Pseudomonas denitrificans pre-cultured (revived from agar plates) under varying conditions (nitrate absent or present; dissolved oxygen absent or present) was subsequently grown aerobically with or without nitrate present, and finally exposed to anoxic conditions (i.e., aeration stopped and dissolved oxygen stripped from solution). The occurrence and length of diauxic lags following transition from aerobic to anoxic conditions were affected strongly

Myrna Gouw; Robert Bozic; Ben Koopman; Spyros A Svoronos

2001-01-01

323

Processing and properties of zirconium diboride-based composites  

Microsoft Academic Search

Two zirconium diboride-base composites were produced and characterised. The chosen starting compositions were: 55 wt.% ZrB2+41 wt.%TiB2+4 wt.% Ni and 83 wt.% ZrB2+13 wt.% B4C+4 wt.% Ni. The microstructure and properties of these composites were compared to those of a monolithic ZrB2+4 wt.% Ni material. In all cases, metallic Ni as the sintering aid promoted the formation of the liquid

F Monteverde; A Bellosi; S Guicciardi

2002-01-01

324

Mechanical Properties of Continuous Fiber Reinforced Zirconium Diboride Matrix Composites  

NASA Technical Reports Server (NTRS)

Continuous fiber reinforced zirconium diboride matrix composites, SCS-9a-(RBSiCZrB2)matrix, are being developed for leading edge, rocket nozzle and turbine engine applications. Recently, the composite materials have been characterized for tensile properties to 1250 C, the highest temperature tested. The tensile properties are fiber dominated as the matrix is microcracked on fabrication, but favorable failure characteristic are observed. Compression and shear mechanical testing results will be reported if completed. The effects of fiber volume fraction and matrix density on mechanical properties will be discussed. The target applications of the materials will be discussed. Specific testing being performed towards qualification for these applications will be included.

Stuffle, Kevin; Creegan, Peter; Nowell, Steven; Bull, Jeffrey D.; Rasky, Daniel J. (Technical Monitor)

1995-01-01

325

Synthesis of NASICON-Type Lithium Zirconium Phosphate  

Microsoft Academic Search

The chemical transformations involved in the synthesis of the NASICON-type compound LiZr2(PO4)3 were studied by thermogravimetry and x-ray diffraction. The results demonstrate that, during heat treatment of a 3Zr(HPO4)2 · 2H2O + Li2CO3 + ZrO2 mixture, the formation of the NASICON phase begins at 600°C. Further heating, however, leads to the concurrent formation of zirconium diphosphate and uncontrolled lithium losses

I. A. Stenina; Yu. A. Velikodnyi; V. A. Ketsko; A. B. Yaroslavtsev

2004-01-01

326

Kinetics of formation of a platelet-reinforced ceramic composite prepared by the directed reaction of zirconium with boron carbide  

SciTech Connect

In this paper the kinetics of formation of a new class of ceramic composite material, zirconium diboride platelet-reinforced zirconium carbides, are discussed. These materials are prepared by the directed reaction of molten zirconium with boron carbide to form a ceramic material composed of zirconium diboride platelets approximately uniformly distributed in a zirconium carbide matrix containing a controlled amount of residual zirconium metal. Results from interrupted growth studies, differential thermal analysis, adiabatic reaction temperature calculations, and kinetic measurements have been used to study the kinetics of the process. The reaction is very fast and proceeds parabolically with time with a rate constant between 1.6 {times} 10{sup {minus}2} and 3.9 {times} 10{sup {minus}2} cm{sup 2}/s. The proposed mechanism suggests that when molten zirconium contacts boron carbide, the molten zirconium exothermically reacts with the boron carbide to form a boron-rick liquid. Further reaction is sustained by the continuous dissolution of the boron carbide as the boron-rich liquid is drawn into the boron carbide. The product is a zirconium diboride/zirconium carbide/zirconium composite which homogenizes quickly at the reaction temperature to yield a uniform product microstructure throughout the composite. Two alternative rate-limiting steps are discussed and the implications of each are explored.

Johnson, W.B.; Nagelberg, A.S.; Breval, E. (Lanxide Corp., Newark, DE (US))

1991-09-01

327

Vulnerability of streams to legacy nitrate sources  

USGS Publications Warehouse

The influence of hydrogeologic setting on the susceptibility of streams to legacy nitrate was examined at seven study sites having a wide range of base flow index (BFI) values. BFI is the ratio of base flow to total streamflow volume. The portion of annual stream nitrate loads from base flow was strongly correlated with BFI. Furthermore, dissolved oxygen concentrations in streambed pore water were significantly higher in high BFI watersheds than in low BFI watersheds suggesting that geochemical conditions favor nitrate transport through the bed when BFI is high. Results from a groundwater-surface water interaction study at a high BFI watershed indicate that decades old nitrate-laden water is discharging to this stream. These findings indicate that high nitrate levels in this stream may be sustained for decades to come regardless of current practices. It is hypothesized that a first approximation of stream vulnerability to legacy nutrients may be made by geospatial analysis of watersheds with high nitrogen inputs and a strong connection to groundwater (e.g., high BFI).

Tesoriero, Anthony J.; Du?, John H.; Saad, David A.; Spahr, Norman E.; Wolock, David M.

2013-01-01

328

?-Pinene Nitrates: synthesis, yields and atmospheric chemistry  

NASA Astrophysics Data System (ADS)

The biogenic volatile organic compound ?-pinene is one of the dominant monoterpenes emitted to the Earth's atmosphere at an estimated rate of ~50 Tg yr-1. Its atmospheric oxidation products in the presence of NO can lead to ozone production, as well as production of secondary organic aerosol (SOA). The major oxidation pathway of ?-pinene is reaction with OH, which in the presence of NO can form either ?-pinene nitrates or convert NO to NO2, which can photolyze to form ozone. In this work, we successfully synthesized four ?-pinene hydroxy nitrates through three different routes, and have identified the 4 individual isomers in ?-pinene/OH/NO reaction chamber experiments. From the experiments, we determined their individual production yields, estimated the total RONO2 yield, and calculated the relative branching ratios of the nitrate precursor peroxy radicals (RO2). The combined yield of the four ?-pinene nitrates was found to be 13.0 (±0.7) % at atmospheric pressure and 296 K, and the total organic nitrate yield was estimated to be 0.19 (+0.10/-0.06). We also determined the OH rate constants for two of the isomers, and have calculated their overall atmospheric lifetimes, which range between 22 and 38 h.

Ma, S. X.; Rindelaub, J. D.; McAvey, K. M.; Gagare, P. D.; Nault, B. A.; Ramachandran, P. V.; Shepson, P. B.

2011-02-01

329

?-Pinene nitrates: synthesis, yields and atmospheric chemistry  

NASA Astrophysics Data System (ADS)

The biogenic volatile organic compound ?-pinene is one of the dominant monoterpenes emitted to the Earth's atmosphere at an estimated rate of ~50 Tg C yr-1. Its atmospheric oxidation products in the presence of NO can lead to ozone production, as well as production of secondary organic aerosol (SOA). The major oxidation pathway of ?-pinene is reaction with OH, which in the presence of NO can form either ?-pinene nitrates or convert NO to NO2, which can photolyze to form ozone. In this work, we successfully synthesized four ?-pinene hydroxy nitrates through three different routes, and have identified these 4 individual isomers in ?-pinene/OH/NO reaction chamber experiments. From the experiments, we determined their individual production yields, estimated the total RONO2 yield, and calculated the relative branching ratios of the nitrate precursor peroxy radicals (RO2). The combined yield of the four ?-pinene nitrates was found to be 0.130 (±0.035) at atmospheric pressure and 296 K, and the total organic nitrate yield was estimated to be 0.19 (+0.10/-0.06). We also determined the OH rate constants for two of the isomers, and have calculated their overall atmospheric lifetimes, which range between 22 and 38 h.

Ma, S. X.; Rindelaub, J. D.; McAvey, K. M.; Gagare, P. D.; Nault, B. A.; Ramachandran, P. V.; Shepson, P. B.

2011-07-01

330

Exclusion of Nitrate from Frozen Aqueous Solutions  

NASA Astrophysics Data System (ADS)

Reactions occurring at the surface of ice, sea ice, and snow in Earth's cryosphere have an impact on the composition of the overlying atmosphere. In order to elucidate reaction mechanisms and model their contributions to atmospheric processes, the morphology of frozen aqueous surfaces and amounts of reactants contained therein must be determined. To this end, the exclusion of nitrate ions to the surface of frozen aqueous solutions has been studied by attenuated total reflection infrared spectroscopy (ATR-IR). In this technique the near-surface region of the frozen films are interrogated to a depth of a few hundred nanometers from the film-crystal interface. Aqueous solutions (0.001 to 0.01 M) of sodium nitrate (NaNO3), magnesium nitrate (Mg(NO3)2), and nitric acid (HNO3) were quickly frozen on the germanium ATR crystal and observed at a constant temperature of about -18°C. In addition to ice and the solutes, liquid water in varying amounts was observed in the spectra. The amount of nitrate in the surface liquid is three to four orders of magnitude higher than in the unfrozen solution. While all the nitrate salts exhibit exclusion to the unfrozen surface, the dynamics are different for different counter-ions. Results are compared to freezing point depression data and the predictions of equilibrium thermodynamics.

Marrocco, H. A.; Michelsen, R. R.

2013-12-01

331

Climate effects of aerosol nitrate from lightning  

NASA Astrophysics Data System (ADS)

The atmospheric aerosol, especially secondary semi-volatile aerosol species, are still a major uncertainty in the assessment of aerosol - climate interactions. In this study, we try to reduce some of the uncertainty by systematically analysing the effects of aerosol nitrate originating from lightning NOx production under present day and preindustrial conditions. As the formation of aerosol nitrate, mostly in the form of NH4NO3, is more efficient at colder temperatures such as in the middle and upper troposphere and lightning represents an upper tropospheric source after chemical conversion of the NOx to HNO3, the vertical distribution of aerosol nitrate can have a substantially different impact on the climate system compared to surface emitted hydrophilic aerosol compounds. To analyse theses effects, we will present decadal global model simulation results, investigating whether the nitrate from lightning in addition to the cooling by additional scattering (direct effect) causes positive or negative indirect aerosol effects. A potential cooling could result from the increase in CCN activity for low clouds, but as the nitrate will also substantially affect the upper troposphere it also plays a role in the IN activity of aerosol particles. Due to coating effects the IN number could be potentially decreased, reducing short wave cloud effects of high clouds.

Tost, Holger; Chang, Dong Yeong; Pringle, Kirsty

2014-05-01

332

Molecular components of nitrate and nitrite efflux in yeast.  

PubMed

Some eukaryotes, such as plant and fungi, are capable of utilizing nitrate as the sole nitrogen source. Once transported into the cell, nitrate is reduced to ammonium by the consecutive action of nitrate and nitrite reductase. How nitrate assimilation is balanced with nitrate and nitrite efflux is unknown, as are the proteins involved. The nitrate assimilatory yeast Hansenula polymorpha was used as a model to dissect these efflux systems. We identified the sulfite transporters Ssu1 and Ssu2 as effective nitrate exporters, Ssu2 being quantitatively more important, and we characterize the Nar1 protein as a nitrate/nitrite exporter. The use of strains lacking either SSU2 or NAR1 along with the nitrate reductase gene YNR1 showed that nitrate reductase activity is not required for net nitrate uptake. Growth test experiments indicated that Ssu2 and Nar1 exporters allow yeast to cope with nitrite toxicity. We also have shown that the well-known Saccharomyces cerevisiae sulfite efflux permease Ssu1 is also able to excrete nitrite and nitrate. These results characterize for the first time essential components of the nitrate/nitrite efflux system and their impact on net nitrate uptake and its regulation. PMID:24363367

Cabrera, Elisa; González-Montelongo, Rafaela; Giraldez, Teresa; Alvarez de la Rosa, Diego; Siverio, José M

2014-02-01

333

Analysis of uranium-zirconium-carbon-oxygen quaternary system for applications in advanced zirconium carbide coated TRISO particles  

NASA Astrophysics Data System (ADS)

The implementation of ZrC for use in oxide TRISO particles for Very High Temperature Reactor (VHTR) conditions to prevent kernel overpressurization and kernel migration has been proposed by several researchers. Analysis is performed incorporating first-principles thermodynamics along with out-of-pile experimental work. UO2+x-U4O9 powders are created and used for in-vacuo thermogravimetric testing with both carbon and zirconium carbide powders to evaluate the efficiency of ZrC for usage as an oxygen getter in oxide TRISO fuels.

Degange, Jonathan Lee

334

Layered zirconium phosphonate with inorganic-organic hybrid structure: Preparation and its assembly with DNA  

NASA Astrophysics Data System (ADS)

An aminoethoxy-functionalized zirconium phosphonate (Zr(O3POCH2CH2NH2)2·3H2O), abbreviated as ZrRP (R=OCH2CH2NH2), with layered structure has been synthesized. This layered compound possesses the characteristic of inorganic-organic hybrid, due to the covalently linked aminoethoxy in the host layer. The anion exchanged property of this zirconium phosphonate is suitable for the direct intercalation of negatively charged DNA, which is different from these reported zirconium phosphates or zirconium phosphonates. As a precursor, this prepared zirconium phosphonate was utilized to fabricate a novel DNA/ZrRP binary hybrid via a delamination-reassembly procedure. The release behavior of DNA from the DNA/ZrRP composite was investigated at different medium pH, because the combination between zirconium phosphonate sheets and DNA was pH-dependent sensitively. Moreover, the helical conformation of DNA was almost retained after the intercalation and release process. These properties of the DNA/ZrRP composite suggested the potential application of layered zirconium phosphonate as a non-viral vector in gene delivery.

Liu, Li-Min; Lu, Guo-Yuan; Jiang, Li-Ping; Zhu, Jun-Jie

2014-07-01

335

Growth and structure of zirconium hydrous polymers in aqueous solutions  

SciTech Connect

Zirconium oxychloride solutions prepared at different pH were heated at elevated temperatures for various aging periods to gain an understanding of the growth mechanism and structure of zirconium hydrous polymers. Small angle X-ray scattering (SAXS) measurements were made on these solutions. It was observed that shape of clusters at the earlier stages of growth is close to a rod rather than a sheet as suggested earlier. The scattering data indicate that a rod-shaped primary particle is formed at pH 1.2, and on an increase in the pH, the primary particles become more branched. On aging more than 1,250 min at 92 C, these primary particles form large aggregates while retaining the primary particle structure. These aggregates, which are mass fractal in nature, restructure while growing in size and eventually transform into dense particles. Scattering data in this study were not enough to determine a specific kinetic growth model of the aggregates because the scattering intensity at low q constantly changes with time during the restructuring process.

Singhal, A. [Oak Ridge National Lab., TN (United States)] [Oak Ridge National Lab., TN (United States); [Univ. of Tennessee, Knoxville, TN (United States). Dept. of Chemistry; Toth, L.M.; Lin, J.S. [Oak Ridge National Lab., TN (United States)] [Oak Ridge National Lab., TN (United States); Beaucage, G. [Univ. of Cincinnati, OH (United States). Dept. of Materials Science and Engineering] [Univ. of Cincinnati, OH (United States). Dept. of Materials Science and Engineering; Peterson, J. [Univ. of Tennessee, Knoxville, TN (United States). Dept. of Chemistry] [Univ. of Tennessee, Knoxville, TN (United States). Dept. of Chemistry

1997-10-15

336

MOCVD of zirconium oxide thin films: Synthesis and characterization  

NASA Astrophysics Data System (ADS)

The synthesis of thin films of zirconia often produces tetragonal or cubic phases, which are stable at high temperatures, but that can be transformed into the monoclinic form by cooling. In the present study, we report the deposition of thin zirconium dioxide films by metalorganic chemical vapor deposition using zirconium (IV)-acetylacetonate as precursor. Colorless, porous, homogeneous and well adherent ZrO 2 thin films in the cubic phase were obtained within the temperature range going from 873 to 973 K. The deposits presented a preferential orientation towards the (1 1 1) and (2 2 0) planes as the substrate temperature was increased, and a crystal size ranging between 20 and 25 nm. The kinetics is believed to result from film growth involving the deposition and aggregation of nanosized primary particles produced during the CVD process. A mismatch between the experimental results obtained here and the thermodynamic prediction was found, which can be associated with the intrinsic nature of the nanostructured materials, which present a high density of interfaces.

Torres-Huerta, A. M.; Domínguez-Crespo, M. A.; Ramírez-Meneses, E.; Vargas-García, J. R.

2009-02-01

337

Retrospective Reactor Dosimetry with Zirconium Alloy Samples in a Pwr  

NASA Astrophysics Data System (ADS)

Retrospective measurements are routinely performed with stainless steel samples. Recent experiments have been successfully conducted using zirconium alloy samples, involving somewhat different neutron activation reactions than are normally encountered with stainless steel samples. The sample alloy compositions consisted of ZIRLO which nominally contains about 1.0% (by weight) niobium, 0.65-1.0% tin, and 0.1% iron, with the balance zirconium. The activation products observed in the samples by gamma spectroscopy included Zr-95, Nb-93m, Nb-95, Sn-113, Sb-125, Mn-54, Co-60, Nb-94, and Ta-182. The niobium was then chemically separated following ASTM procedure El297 and the Nb-93m activities were measured by x-ray spectroscopy. The thermal neutron fluences, as determined independently by the neutron capture gamma reactions to Zr-95, Sn-113, Nb-94, and Sn/Sb-125, were in excellent agreement. The fast neutron fluences, as determined separately by the Fe-54(n,p)Mn-54 and Nb-93(n,n')Nb-93m reactions, were also in good agreement, thus demonstrating the versatility of the retrospective dosimetry technique. The results were used to experimentally determine the fast and thermal fluxes in the Vogtle unit 2 PWR.

Greenwood, L. R.; Foster, J. P.

2009-08-01

338

Evidence for an ideal transparent anodic oxide film on zirconium  

SciTech Connect

The properties of a transparent oxide formed on zirconium by anodic oxidation in carbonate buffer are described. The transparent oxide has all the properties of an ideal valve-metal oxide. The film grows via a high field conduction mechanism. The potential and film thickness both increase linearly with time under constant-current growth conditions to well over 100 V with no sign of electronic leakage or breakdown. When the oxide is grown at a current density of 93 {mu}A/cm{sup 2}, the electric field in the oxide is 4.1 MV/cm, and the oxide is anisotropic with n{sub z} = 2.278 parallel and n{sub x} = 2.296 perpendicular to the field. The relative permittivity is 38.3 at the anodizing field, and the oxide shows electrostrictive effects similar to those exhibited by other valve-metal oxides with high relative permittivities. Both the refractive index and the relative permittivity increase when the field is removed, and there is a corresponding decrease in film thickness of just under 1%. Cathodic reduction inserts hydrogen into the oxide to a limited depth, and the outer layer thus formed is optically absorbing. Subsequent anodic oxidation removes the hydrogen and returns the film to its initial transparent state. The present study was carried out as part of an investigation comparing films formed anodically with films formed in steam on zirconium-based reactor tube materials.

Ord, J.L.; Smet, D.J. De [Univ. of Waterloo, Ontario (Canada). Dept. of Physics

1995-03-01

339

Reaction of Titanium and Zirconium Particles in Cylindrical Explosive Charges  

NASA Astrophysics Data System (ADS)

The critical conditions for the reaction of high melting-point metallic particles (Ti, Zr) dispersed during the detonation of long cylindrical explosive charges have been investigated experimentally. The charges consisted of packed beds of either spherical titanium particles (with diameters of 35, 90, or 215 ?m; AP&C, Inc.) or nonspherical zirconium particles (250 -- 500 ?m or 500 -- 600 ?m, Atlantic Equipment Eng., NJ) saturated with sensitized liquid nitromethane. For the titanium particles, a threshold particle diameter exists, above which self-sustained particle reaction is not observed, although some particle reaction occurs immediately behind the detonation front then rapidly quenches. For the smallest particles, the proportion of the conical particle cloud that reacts increases with charge diameter, suggesting that the reaction initiation is a competition between particle heating and expansion cooling of the products. For zirconium particles, no critical conditions exist; particle ignition was observed for all particle and charge diameters tested. In this case, interaction of the high pressure detonation wave with the particles is sufficient to initiate reaction at the particle surface after a delay time (˜ 10's ?s), which is much less than the time required for thermal equilibration of the particles.

Frost, David; Cairns, Malcolm; Goroshin, Samuel; Zhang, Fan

2007-06-01

340

Characterization of SAES St198 zirconium-iron-tin alloy  

SciTech Connect

A waste minimization program to develop a non-oxidative stripper system based on metallic getters is being conducted. Initial development is being performed using a Zr-Fe-Sn intermetallic alloy getter procured as Stl98 from SAES Gefters/USA., Inc. This memorandum describes characterizations of physical and compositional properties of SAES Stl98. SAES Stl98 getter was supplied as very durable, cylindrical pellets made by compaction of. granules of Zr-Fe-Sn alloy up to 150 {mu}m in size. Pellet density was 5.2 g/mL corresponding to 24.8% open porosity and very little closed porosity. Bulk composition of Stl98 was 73.6 weight percent (w/o) Zr, 23.3 w/o Fe and 1.2 w/o Sn. Stl98 consists of Zr{sub 2}Fe primary phase along with four secondary phases (ZrFe{sub 2}, Zr{sub 5}FeSn, {alpha}-zirconium, and {eta}-Zr{sub 4}Fe{sub 2}O{sub 0.6}). Hydriding characteristics of Stl98 are expected to differ slightly from those of Zr{sub 2}Fe because {alpha}-zirconium and, possibly, Zr{sub 5}FeSn also react with hydrogen.

Mosley, W.C.

1992-10-13

341

Characterization of SAES St198 zirconium-iron-tin alloy  

SciTech Connect

A waste minimization program to develop a non-oxidative stripper system based on metallic getters is being conducted. Initial development is being performed using a Zr-Fe-Sn intermetallic alloy getter procured as Stl98 from SAES Gefters/USA., Inc. This memorandum describes characterizations of physical and compositional properties of SAES Stl98. SAES Stl98 getter was supplied as very durable, cylindrical pellets made by compaction of. granules of Zr-Fe-Sn alloy up to 150 [mu]m in size. Pellet density was 5.2 g/mL corresponding to 24.8% open porosity and very little closed porosity. Bulk composition of Stl98 was 73.6 weight percent (w/o) Zr, 23.3 w/o Fe and 1.2 w/o Sn. Stl98 consists of Zr[sub 2]Fe primary phase along with four secondary phases (ZrFe[sub 2], Zr[sub 5]FeSn, [alpha]-zirconium, and [eta]-Zr[sub 4]Fe[sub 2]O[sub 0.6]). Hydriding characteristics of Stl98 are expected to differ slightly from those of Zr[sub 2]Fe because [alpha]-zirconium and, possibly, Zr[sub 5]FeSn also react with hydrogen.

Mosley, W.C.

1992-10-13

342

Dispersion type zirconium matrix fuels fabricated by capillary impregnation method  

NASA Astrophysics Data System (ADS)

Several novel dispersion fuel compositions with a high uranium content fuel (U9Mo, U5Zr5Nb, U 3Si) and a zirconium alloy matrix with low melting point (1063-1133 K) have been developed at A.A. Bochvar Institute using a capillary impregnation fabrication method. The capillary impregnation method introduces fuel granules and granules of a zirconium alloy into a fuel element followed by a short-term anneal at a temperature above the melting temperature of alloy. The alloy melts down and under capillary forces moves into the joints between the fuel element components to form metallurgical bonds. The volume ratios between the components are: 55-65% fuel, 10-20% matrix, and 15-30% pores. Fuel elements produced by capillary impregnation method have a high uranium content (9-10 g cm -3) and a high thermal conductivity (18-22 W m -1 K -1), which, when used as PWR or BWR fuels allow the fuel temperature to be lowered to 723-773 K. They also feature porosity to accommodate swelling. The metallurgical fuel-cladding bond makes the fuel elements serviceable in power transients. The primary advantages for PWR, BWR and CANDU use of these fuels elements, would be the high uranium content, low fuel temperature and serviceability under transient conditions. Consideration is given to their applicability in Floating Nuclear Power Plants (FNPP) as well as for the feasibility of burning civil and weapon grade plutonium.

Savchenko, A.; Konovalov, I.; Vatulin, A.; Morozov, A.; Orlov, V.; Uferov, O.; Ershov, S.; Laushkin, A.; Kulakov, G.; Maranchak, S.; Petrova, Z.

2007-05-01

343

On the mechanisms of carbon monoxide reduction with zirconium hydrides  

SciTech Connect

Results of studies to prepare dinitrogen complexes of zirconium led to the synthesis of a crystalline N/sub 2/ adduct of bis(pentamethylcyclopentadienyl)zirconium, ((eta/sup 5/-C/sub 5/Me/sub 5/)/sub 2/ZrN/sub 2/)/sub 2/N/sub 2/(1), which when treated with CO yielded sequentially ((eta/sup 5/-C/sub 5/Me/sub 5/)/sub 2/Zr(CO))/sub 2/N/sub 2/ and (eta/sup 5/-C/sub 5/Me/sub 5/)/sub 2/Zr(CO)/sub 2/. Reaction of the latter compound with H/sub 2/ was found to proceed according to the reaction (eta/sup 5/-C/sub 5/Me/sub 5/)/sub 2/Zr(CO)/sub 2/ + H/sub 2/ ..-->.. (eta/sup 5/-C/sub 5/Me/sub 5/)/sub 2/Zr(H)(OCH/sub 3/) + CO (2 atm, 110/sup 0/C). Results of studies of the mechanisms of this reaction are reported. Olefins, acetylenes, nitriles, isocyanides, and H/sub 2/, as well as CO, rapidly displace the N/sub 2/ in 1 to yield a variety of stable adducts. Possible mechanisms for these related reactions are also suggested. (BLM)

Wolczanski, P.T.; Bercaw, J.E.

1980-04-01

344

Properties of zirconium carbide for nuclear fuel applications  

NASA Astrophysics Data System (ADS)

Zirconium carbide (ZrC) is a potential coating, oxygen-gettering, or inert matrix material for advanced high temperature reactor fuels. ZrC has demonstrated attractive properties for these fuel applications including excellent resistance against fission product corrosion and fission product retention capabilities. However, fabrication of ZrC results in a range of stable sub-stoichiometric and carbon-rich compositions with or without substantial microstructural inhomogeneity, textural anisotropy, and a phase separation, leading to variations in physical, chemical, thermal, and mechanical properties. The effects of neutron irradiation at elevated temperatures, currently only poorly understood, are believed to be substantially influenced by those compositional and microstructural features further adding complexity to understanding the key ZrC properties. This article provides a survey of properties data for ZrC, as required by the United States Department of Energy's advanced fuel programs in support of the current efforts toward fuel performance modeling and providing guidance for future research on ZrC for fuel applications. Carbon-to-zirconium ratio (the product stoichiometry). Chemical impurities. Presence of secondary phases including grain boundary phases. Grain size, morphology, orientation, and texture. Porosity and pore size, distribution, and morphology. Other forms of defects

Katoh, Yutai; Vasudevamurthy, Gokul; Nozawa, Takashi; Snead, Lance L.

2013-10-01

345

Wear Analysis in THA Utilizing Oxidized Zirconium and Crosslinked Polyethylene  

PubMed Central

Oxidized zirconium, a material with a ceramic surface on a metal substrate, and highly cross-linked polyethylene are two materials developed to reduce wear. We measured in vivo femoral head penetration in patients with these advanced bearings. We hypothesized the linear wear rates would be lower than those published for cobalt-chrome and standard polyethylene. We retrospectively reviewed a select series of 56 THAs in a relatively young, active patient population utilizing oxidized zirconium femoral heads and highly cross-linked polyethylene acetabular liners. Femoral head penetration was determined using the Martell computerized edge-detection method. All patients were available for 2-year clinical and radiographic followup. True linear wear was 4 ?m/year (95% confidence intervals, ± 59 ?m/year). The early wear rates in this cohort of relatively young, active patients were low and we believe justify the continued study of these alternative bearing surfaces. Level of Evidence: Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Garvin, Kevin L.; Mangla, Jimmi; Murdoch, Nathan; Martell, John M.

2008-01-01

346

Hydrogen pickup measurements in zirconium alloys: Relation to oxidation kinetics  

NASA Astrophysics Data System (ADS)

The optimization of zirconium-based alloys used for nuclear fuel cladding aims to reduce hydrogen pickup during operation, and the associated cladding degradation. The present study focuses on precisely and accurately measuring hydrogen pickup fraction for a set of alloys to specifically investigate the effects of alloying elements, microstructure and corrosion kinetics on hydrogen uptake. To measure hydrogen concentrations in zirconium alloys two techniques have been used: a destructive technique, Vacuum Hot Extraction, and a non-destructive one, Cold Neutron Prompt Gamma Activation Analysis. The results of both techniques show that hydrogen pickup fraction varies significantly with exposure time and between alloys. A possible interpretation of the results is that hydrogen pickup results from the need to balance charge. That is, the pickup of hydrogen shows an inverse relationship to oxidation kinetics, indicating that, if transport of charged species is rate limiting, oxide transport properties such as oxide electronic conductivity play a key role in the hydrogen pickup mechanism. Alloying elements (either in solid solution or in precipitates) would therefore impact the hydrogen pickup fraction by affecting charge transport.

Couet, Adrien; Motta, Arthur T.; Comstock, Robert J.

2014-08-01

347

Measuring Nitrates and Their Effect on Water Quality  

NSDL National Science Digital Library

This module on measuring nitrates and their effects on water quality is from a larger series on water quality investigations. It provides background information on nitrates and how it affects water quality. It also contains both a pre-test and post-test, a laboratory investigation, and a self-study game. The purpose of the site is to help students understand the sources of nitrates and the role that nitrates play in an ecosystem, describe the effects of excess nitrates on water quality and human health, and teach students how to measure, graph, and interpret the direct and indirect effects of nitrates on fish.

Johnson, Larry

348

Techniques for Measurement of Nitrate Movement in Soils  

NASA Technical Reports Server (NTRS)

Contamination of surface and ground waters with nitrate usually involves leaching through soil of nitrate produced by mineralization of soil organic matter, decomposition of animal wastes or plant residues, or derived from fertilizers. Nitrate concentrations in the soil solution may be measured by several chemical procedures or by the nitrate electrode. since nitrate is produced throughout the soil mass it is difficult to identify a source of nitrate contamination by conventional means. This problem can be solved by use of N-15-enriched or N-15-depleted materials as tracers. The latter is particularly attractive because of the negligible possibility of the tracer hazardous to health.

Broadbent, F. E.

1971-01-01

349

Nitrate isotope fractionations during biological nitrate reduction: Insights from first principles theoretical modeling  

NASA Astrophysics Data System (ADS)

Coupled fractionations of N and O isotopes during biological nitrate reduction provide important constraints on the marine nitrogen cycle at present and in the geologic past. Recent laboratory experiments with mono-cultures of nitrate-assimilative algae and plankton, and denitrifying bacteria demonstrate that N and O isotopic compositions of the residual nitrate co-vary linearly with a constant ratio (i.e., ??18O: ??15N) of ~1 or ~0.6 [1]. These systematic variations have been inferred to derive from the kinetic isotope fractionations associated with nitrate reductases. The isotope fractionation mechanisms at the enzymatic level, however, remain elusive. Here we present models of isotope fractionations accompanying the nitrate reduction (NO3-?NO2-) by three functional types of nitrate reductases, using techniques from ab initio, transition state and statistical thermodynamic theory. We consider three types of nitrate reductases: eukNR (eukaryotic assimilatory nitrate reductase), NAR (prokaryotic respiratory nitrate reductase) and Nap (prokaryotic periplasmic nitrate reductase). All are penta- or hexa-coordinated molybdo-enzymes, but bear considerable differences in protein geometry among functional types. Our models, based on the simplified structures of their active sites, predict N and O isotope effects (15? and 18?) ranging from 32.7 to 36.6‰ and from 33.5 to 34.8‰, respectively, at 300K with 18?:15? ratios of 0.9-1.1. The predicted amplitudes of N and O isotope fractionations are in the range measured for eukNR in vitro (~27‰, Karsh et al. in prep), and also correspond to the upper amplitudes observed for denitrifiers in vivo (~25‰, [1]). Moreover, the computed 18?:15? ratios corroborate the consistent relationships of ~1 observed experimentally for eukNR and the respiratory NAR. These findings indicate the enzymatic reduction is likely the rate-limiting step in most biological nitrate reductions. In addition, the predicted similarity of 18?:15? ratios among different nitrate reductases suggests that the nitrate isotope fractionations by nitrate reductases are governed by the kinetics of the O-N bond cleavage, which incurs negligible differences from variations in surrounding moieties at the active sites. However, our model similarly predicts a 15? of 36.6‰ and 18?:15? of 0.9 for the auxiliary Nap, although it exhibits a 15? of ~15‰ and 18?:15? of ~0.6 in vivo [1]. This discrepancy is suspected to arise from slower binding and release of NO3- from Nap, which could be partially rate-determining in this enzymatic catalysis, or from the assumptions of our modeled enzyme structures. By extending our above models to include the multiply-substituted (clumped) isotopologues, we predict that isotope fractionations during biological nitrate reduction decrease the proportion of 15N-18O bonds in the residual nitrate relative to their expected equilibrium abundances (~0.02‰ decrease for every 1‰ kinetic enrichment in nitrate ?15N). Future quantification of 15N-18O clumped isotope anomalies in natural nitrate may provide additional constraints on the nitrogen cycle in the ocean. Reference: [1] Granger et al. (2010) GCA, 74: 1030-1040.

Guo, W.; Granger, J.; Sigman, D. M.

2010-12-01

350

Pustular allergic contact dermatitis to isoconazole nitrate.  

PubMed

The topical imidazole antimycotics are widely used and are an infrequent cause of contact allergy. We report on a woman, who developed an unusual clinical picture of allergic contact dermatitis, namely papulo-pustular reaction, evoked by an isoconazole nitrate-containing cream. The histopathologic changes included subcorneal pustules, spongiosis, and an inflammatory infiltrate composed mainly of lymphocytes and some eosinophils and neutrophils. The patient demonstrated a severe vesicular reaction to isoconzole nitrate as is and at an imidazoles concentration of 0.5%. No cross-reactivity with other imidazole antimycotics was noted. PMID:9358116

Lazarov, A; Ingber, A

1997-12-01

351

A Reservoir of Nitrate Beneath Desert Soils  

USGS Publications Warehouse

A large reservoir of bioavailable nitrogen (upto ???104 kilograms of nitrogen per hectare, as nitrate) has been previously overlooked in studies of global nitrogen distribution. The reservoir has been accumulating in subsoil zones of and regions throughout the Holocene. Consideration of the subsoil reservoir raises estimates of vadose-zone nitrogen inventories by 14 to 71% for warm deserts and arid shrublands worldwide and by 3 to 16% globally. Subsoil nitrate accumulation indicates long-term leaching from desert soils, impelling further evaluation of nutrient dynamics in xeric ecosystems. Evidence that subsoil accumulations are readily mobilized raises concern about groundwater contamination after land-use or climate change.

Walvoord, M. A.; Phillips, F. M.; Stonestrom, D. A.; Evans, R. D.; Hartsough, P. C.; Newman, B. D.; Striegl, R. G.

2003-01-01

352

Methylhydrazinium nitrate. [rocket plume deposit chemistry  

NASA Technical Reports Server (NTRS)

Methylhydrazinium nitrate was synthesized by the reaction of dilute nitric acid with methylhydrazine in water and in methanol. The white needles formed are extremely hygroscopic and melt at 37.5-40.5 C. The IR spectrum differs from that reported elsewhere. The mass spectrum exhibited no parent peak at 109 m/z, and thermogravimetric analysis indicated that the compound decomposed slowly at 63-103 C to give ammonium and methylammonium nitrate. The density is near 1.55 g/cu cm.

Lawton, E. A.; Moran, C. M.

1983-01-01

353

The Acid Catalyzed Nitration of Methanol: Formation of Methyl Nitrate via Aerosol Chemistry  

NASA Technical Reports Server (NTRS)

The liquid phase acid catalyzed reaction of methanol with nitric acid to yield methyl nitrate under atmospheric conditions has been investigated using gas phase infrared spectroscopy. This nitration reaction is expected to occur in acidic aerosol particles found in the upper troposphere/lower stratosphere as highly soluble methanol and nitric acid diffuse into these aerosols. Gaseous methyl nitrate is released upon formation, suggesting that some fraction of NO(x) may he liberated from nitric acid (methyl nitrate is later photolyzed to NO(x)) before it is removed from the atmosphere by wet deposition. Thus, this reaction may have important implications for the NO(x) budget. Reactions have been initiated in 45-62 wt% H2SO4 solutions at 10.0 C. Methyl nitrate production rates increased exponentially with acidity within the acidity regime studied. Preliminary calculations suggest that the nitronium ion (NO2(+) is the active nitrating agent under these conditions. The reaction order in methanol appears to depend on the water/methanol ratio and varies from first to zeroth order under conditions investigated. The nitration is first order in nitronium at all acidities investigated. A second order rate constant, kappa(sub 2), has been calculated to be 1 x 10(exp 8)/ M s when the reaction is first order in methanol. Calculations suggest the nitration is first order in methanol under tropospheric conditions. The infinitesimal percentage of nitric acid in the nitronium ion form in this acidity regime probably makes this reaction insignificant for the upper troposphere; however, this nitration may become significant in the mid stratosphere where colder temperatures increase nitric acid solubility and higher sulfuric acid content shifts nitric acid speciation toward the nitronium ion.

Riffel, Brent G.; Michelsen, Rebecca R.; Iraci, Laura T.

2004-01-01

354

Products of the OH radical-initiated reactions of 2-propyl nitrate, 3-methyl-2-butyl nitrate and 3-methyl-2-pentyl nitrate  

NASA Astrophysics Data System (ADS)

In the atmosphere, alkyl nitrates formed from the reactions of alkyl peroxy radicals with NO are chemically removed by photolysis and by reaction with OH radicals. Products of the gas-phase reactions of OH radicals with 2-propyl nitrate, 3-methyl-2-butyl nitrate and 3-methyl-2-pentyl nitrate at room temperature have been investigated. The products observed and quantified were: from 2-propyl nitrate, acetone (58 ± 18%); from 3-methyl-2-butyl nitrate, acetaldehyde (113 ± 39% from gas chromatographic analyses and 70 ± 25% from FT-IR analyses), acetone (55 ± 8%), and 3-methyl-2-butanone (17 ± 2%); and from 3-methyl-2-pentyl nitrate, acetaldehyde (120 ± 26% from gas chromatographic analyses and 80 ± 21% from FT-IR analyses), propanal (?1.1%), 2-butanone (33 ± 3%), 2-methylbutanal (?1.1%), and 3-methyl-2-pentanone (9 ± 1%), where the percentage molar yields are given in parentheses. Using these measured product yields together with predicted reaction schemes indicates that these products account for 58 ± 18%, 86 ± 15% and 63 ± 7% of the overall reaction pathways of the 2-propyl nitrate, 3-methyl-2-butyl nitrate and 3-methyl-2-pentyl nitrate reactions, respectively. The NO 2 present in the -ONO 2 group in these nitrates will be released in the reaction pathways leading to the observed products.

Aschmann, Sara M.; Tuazon, Ernesto C.; Arey, Janet; Atkinson, Roger

2011-03-01

355

Ligand exchange chromatography of free amino acids and proteins on porous microparticulate zirconium oxide  

SciTech Connect

The Lewis acid sites present on the underlying zirconium oxide particles are responsible for the unusual elution sequence for amino acids on copper loaded, phosphated zirconium oxide supports reported in an earlier study. To more thoroughly examine the effect of these strong Lewis acid sites in this paper. The authors have studied ligand exchange chromatography on copper loaded zirconium oxide particles. It is shown here that carboxylate functional groups on amino acid solutes strongly interact with surface Lewis acid sites. Addition of competing hard Lewis bases to the eluent attenuates these specific interactions. The result is a chromatographic system with high selectivity which is also suitable for ligand exchange chromatography of proteins.

Blackwell, J.A. (13M Co., Specialty Adhesives and Chemicals Div., St. Paul, MN (United States)); Carr, P.W. (Dept. of Chemistry, Inst. for Advanced Studies in Bioprocess Technology, Univ. of Minnesota, Minneapolis, MN (United States))

1992-01-01

356

Physicomechanical properties of the surface of a zirconium alloy modified by a pulsed ion beam  

NASA Astrophysics Data System (ADS)

The physicomechanical properties of the surface of the Zr-1% Nb zirconium alloy modified by a pulsed carbon ion beam with a pulse duration of 80 ns, an energy of 200 keV, and a current density of 120 A/cm2 are studied at four regimes having different numbers of pulses. Irradiation by a carbon ion beam results in hardening of the surface layer to a depth of 2 ?m, grain refinement to 0.15-0.8 ?m, zirconium carbide formation, and a decrease in the hydrogen permeability of the zirconium alloy.

Chernov, I. P.; Berezneeva, E. V.; Beloglazova, P. A.; Ivanova, S. V.; Kireeva, I. V.; Lider, A. M.; Remnev, G. E.; Pushilina, N. S.; Cherdantsev, Yu. P.

2014-04-01

357

Mammalian nitrate biosynthesis: mouse macrophages produce nitrite and nitrate in response to Escherichia coli lipopolysaccharide  

Microsoft Academic Search

Escherichia coli lipopolysaccharide (LPS)-induced nitrate biosynthesis was studied in LPS-sensitive C3H\\/He and LPS-resistant C3H\\/HeJ mice. Intraperitoneal injection of 15 ..mu..g of LPS led to a temporary 5- to 6-fold increase in blood nitrate concentration in the C3H\\/He strain. Levels of nitrate excreted in the urine were also increased. In contrast, no increase was observed in the C3H\\/HeJ strain with LPS

D. J. Stuehr; M. A. Marletta

1985-01-01

358

SOME DATE ON THE ANALYSIS OF URANIUM, THORIUM, AND ZIRCONIUM  

Microsoft Academic Search

Considering the physicochemical conditions for tributyl phosphate (TBP) ; uranium extraction, an optimum nitrate concentration of the aqueous phase is ; found, in which uranium separation by single extraction amounts virtually to 100%. ; The extraction is carried out in TBP-petrol solution and the uranium is re-; extracted in a dilute ammonium carbonate solution. The uranium content can be ;

G. Almassy; M. Oerdoegh; A. Schneer

1958-01-01

359

Investigation of desert subsoil nitrate in Northeastern Badia of Jordan.  

PubMed

High levels of naturally occurring nitrate were observed under desert pavement surfaces in NE Badia of Jordan. The subsoil nitrate inventory varies from about 24,351 to 28,853 kg NO(3)(-)/ha to a depth of 60 cm which is more than two times greater than nitrate in nonpavement soils, although both soils occurred within similar landscape and microclimate conditions. The results indicated that pavement particle size and cover percent are the primary factors contributing to the observed variations in nitrate accumulation. Desert pavement soils fully covered with fine clasts showed higher nitrate concentrations compared to soils moderately covered with coarse-grained pavements. The results also showed that high levels of nitrate were generally reached between 20 and 30 cm depth before the concentrations decreased. Chloride showed distribution profiles similar to those of nitrate. No observable difference was observed in nitrate level under desert pavement with abundant lichens compared to non-lichen pavement surface. PMID:23178770

Al-Taani, Ahmed A; Al-Qudah, Khaldoun A

2013-01-01

360

Desilylative Nitration of Alkyl- and Allylsilanes with Nitronium Salts,  

National Technical Information Service (NTIS)

Desilylative nitration of methyl- and ethyl- silanes with nitronium tetrafluoroborate in sulfolane solution gives nitromethane and nitroethane, respectively. Higher alkylsilanes are also nitrated, but the reactions are followed by HNO2 elimination. The me...

G. A. Olah C. Rochin

1987-01-01

361

CURRENT METHODS TO MEASURE ATMOSPHERIC NITRIC ACID AND NITRATE ARTIFACTS  

EPA Science Inventory

Presentations given at a workshop on 'Measurement of Atmospheric Nitrates' (Southern Pines, N.C. October 3-4, 1978) are documented. The authors consider various analytical methods to measure ambient concentrations of nitric acid and artifact nitrate formation....

362

Pepsin is nitrated in the rat stomach, acquiring antiulcerogenic activity: a novel interaction between dietary nitrate and gut proteins.  

PubMed

Dietary nitrate is reduced to nitrite and nitric oxide ((•)NO) in the gut, producing reactive species able to nitrate proteins and lipids. We investigated intragastric production of (•)NO and nitrating agents in vivo by examining selective nitration of pepsinogen and pepsin. We further addressed the functional impact of nitration on peptic activity by evaluating the progression of secretagogue-induced ulcers. Pepsinogen nitration was assessed in healthy and diclofenac-induced ulcerated rat stomachs. Both groups were fed nitrite or water by oral gavage. Protein nitration was studied by immunofluorescence and immunoprecipitation. In parallel experiments, pentagastrin was administered to rats and nitrite was then instilled intragastrically. (•)NO levels were measured before and after nitrite administration by chemiluminescence. Macroscopic damage was assessed and nitrated pepsin was examined in the margin of ulcers. Protein nitration was detected physiologically in the stomach of healthy animals. Nitrite had a dual effect on intragastric nitration: overall nitration was decreased under physiological conditions but enhanced by acute inflammation. Pepsin and pepsinogen were also nitrated via a nitrite-dependent pathway. Nitration of both pepsin and its zymogen led to decreased peptic activity in response to classical substrates (e.g., collagen). Under conditions of acute ulceration, nitrite-dependent pepsin nitration prevented the development of gastric ulcers. Dietary nitrite generates nitrating agents in the stomach in vivo, markedly decreasing peptic activity. Under inflammatory and ulcerogenic conditions pepsin nitration attenuates the progression of gastric ulceration. These results suggest that dietary nitrite-dependent nitration of pepsin may have a novel antiulcerogenic effect in vivo. PMID:23277149

Rocha, Bárbara S; Gago, Bruno; Barbosa, Rui M; Lundberg, Jon O; Mann, Giovanni E; Radi, Rafael; Laranjinha, João

2013-05-01

363

Surface Area of Powdered Cerous Magnesium Nitrate.  

National Technical Information Service (NTIS)

The surface area of cerous magnesium nitrate has been measured at 77K by a nitrogen adsorption technique. The result shows that the anomalously small Kapitza resistance between this substance and liquid He3 at low temperatures is not due to an anomalously...

D. F. Brewer J. P. Harrison M. P. Bertinat

1969-01-01

364

Detonation Performance of Aluminium - Ammonium Nitrate Explosives  

Microsoft Academic Search

The research on an effect of aluminium contents on detonation characteristics of ammonium nitrate explosives was carried out. Measurements of detonation velocity were performed. Parameters of blast waves produced by charges of the investigated explosives detonating in an open space were measured by the use of piezoelectric gauges. Quasi-static pressure measurements were conducted in a steel chamber of 0.15 m

Józef PASZULA; Waldemar A. TRZCI?SKI

365

PEROXYCHLOROFORMYL NITRATE: SYNTHESIS AND THERMAL STABILITY  

EPA Science Inventory

Peroxychloroformyl nitrate, ClC(O)OONO2, has been identified as the principal product of the ultraviolet irradiation of Cl2, NO2, and CO mixtures in air. Fourier Transform IR spectroscopic detection methods have been used to identify the newly detected compound and to establish i...

366

A toxicological study of gadolinium nitrate  

SciTech Connect

The sensitization study in the guinea pig did not show gadolinium nitrate to have potential sensitizing properties. Skin application studies in the rabbit demonstrated that it was cutaneously a severe irritant. This material was considered an irritant in the rabbit eye application studies. 3 refs., 1 tab.

London, J.E.

1988-05-01

367

Pyrex Membrane Potential in Binary Nitrate Melts.  

National Technical Information Service (NTIS)

Emf measurements are reported at 350C for cells with a Pyrex membrane and containing binary nitrate melts of the type MNO3 - AgNO3. The ion exchange model fits the data whereas the liquid junction model does not. Selectivity constants have the same order ...

A. G. Keenan K. Notz F. L. Wilcox

1967-01-01

368

Nitrate induced anaemia in home dialysis patients.  

PubMed

Many home dialysis patients in Florence and the surrounding area suddenly showed an unusual anaemia. All used a softener for water treatment. They demonstrated methaemoglobinaemia, Heinz bodies and reduction in plasma haptoglobin indicating Hb oxidation. Tap water analysis showed excessive nitrates. The substitution of the softeners with deionisers solved this important and unusual clinical problem. PMID:3991518

Salvadori, M; Martinelli, F; Comparini, L; Bandini, S; Sodi, A

1985-01-01

369

Standoff Raman measurement of nitrates in water  

NASA Astrophysics Data System (ADS)

The identification and real time detection of explosives and hazardous materials are of great interest to the Army and environmental monitoring/protection agencies. The application and efficiency of the remote Raman spectroscopy system for real time detection and identification of explosives and other hazardous chemicals of interest, air pollution monitoring, planetary and geological mineral analysis at various standoff distances have been demonstrated. In this paper, we report the adequacy of stand-off Raman system for remote detection and identification of chemicals in water using dissolved sodium nitrate and ammonium nitrate for concentrations between 200ppm and 5000ppm. Nitrates are used in explosives and are also necessary nutrients required for effective fertilizers. The nitrates in fertilizers are considered as potential sources of atmospheric and water pollution. The standoff Raman system used in this work consists of a 2-inch refracting telescope for collecting the scattered Raman light and a 785nm laser operating at 400mW coupled with a small portable spectrometer.

Sadate, S.; Kassu, A.; Farley, C. W.; Sharma, A.; Hardisty, J.; Lifson, Miles T. K.

2011-09-01

370

Nitrate Salt Immobilization Process Development and Implementation.  

National Technical Information Service (NTIS)

The waste nitrate salts generated at the Rocky Flats Plant (RFP) were determined to be unacceptable in their present form for shipment to and storage at the Nevada Test Site, according to the recently implemented Waste Acceptance Criteria. A reduction in ...

R. D. Petersen A. J. Johnson K. G. Peter

1986-01-01

371

Thorium Nitrate Stockpile from Here to Eternity.  

National Technical Information Service (NTIS)

The Defense National Stockpile Center (DNSC), a field level activity of the Defense Logistics Agency (DLA) has stewardship of a stockpile of thorium nitrate that has been in storage for decades. The stockpile is made up of approximately 3.2 million kg (7 ...

W. H. Hermes T. D. Hylton C. H. Mattus S. N. Storch P. S. Singely J. W. Terry M. Pecullan F. K. Reilly

2003-01-01

372

Dietary exposure models for nitrates and nitrites  

Microsoft Academic Search

Models to assess dietary exposure of population groups to nitrates and nitrites should be based on the major sources of these substances in foods. Most models require the use of food consumption information and will, therefore, be flawed by the problems that exist with current dietary intake assessment methods. The Total Diet Study model would probably not provide representative coverage

Jean A. T. Pennington

1998-01-01

373

4-Meth-oxy-anilinium nitrate  

PubMed Central

The title compound, C7H10NO+·NO3 ?, crystallized with two p-ansidinium cations and two nitrate anions in the asymmetric unit. As well as Columbic and van der Waals forces, moleucles inter­act via multiple bifurcated N—H?O hydrogen bonds that help consolidate the crystal packing, resulting in a three-dimensional network.

Rahmouni, Hajer; Smirani Sta, Wajda; Al-Deyab, S. Salem; Rzaigui, Mohamed

2011-01-01

374

Analysis of nitrated polycyclic aromatic hydrocarbons  

Microsoft Academic Search

Many nitrated polycyclic aromatic hydrocarbons (NPAH) that are present in low concentrations in the environment and in emission\\u000a sources have been shown to be mutagenic and\\/or carcinogenic. This paper reviews the current methods of analysis of these compounds\\u000a with the emphasis on NPAH measurements in ambient particulate matter samples.

Barbara Zielinska; Shar Samy

2006-01-01

375

Regulatory Impact Statement: Nitrate and Nitrite.  

National Technical Information Service (NTIS)

The economic impacts of a proposed label rule change to allow the sale of nitrate and nitrite-free processed meat products by their familiar product names in traditional cured meat product markets were assessed. Three options were evaluated to determine t...

R. J. Lenahan C. R. Burbee

1979-01-01

376

Kinetics of Thermal Dissociation of Hydrazine Nitrate.  

National Technical Information Service (NTIS)

On a micro-calorimeter in intervals of 194-254C the kinetic reaction of thermal dissociation of hydrazine nitrate has been investigated. The reaction accelerates whereupon the amount of acceleration depends upon m/V. The kinetic parameters of the reaction...

Y. I. Rubtsov G. B. Manelis

1975-01-01

377

Atmospheric nitrate formation: A mechanistic study  

NASA Astrophysics Data System (ADS)

The peroxy radical (RO_2) + NO reaction sits at the center of tropospheric chemistry. The primary reaction products are RO and NO_2, forming odd oxygen and propagating the radical chain. However, organic nitrates (RONO_2) are also known to form, with a general pattern of increasing nitrate yields with increasing carbon number and decreasing temperature. There is also a marked pressure dependence to the nitrate yields. These reactions almost certainly proceed through a common peroxynitrite (ROONO) intermediate, which is highly vibrationally excited. It is vital that we understand this mechanism, because nitrate formation is a major radical termination pathway. Of particular interest are substituted peroxynitrates, such as those formed during the oxidation of isoprene and monoterpenes. We shall argue that experimental data are consistent with a mechanism involving partial collisional stabilization of this intermediate, followed by rapid thermal decomposition. We shall present master equation calculations supporting this conclusion. A strong and testable prediction from this study is that radical propagation will virtually shut down for high carbon number peroxy radicals at low temperatures.

Donahue, N.; Zhang, J.

2003-04-01

378

SOIL DEVELOPMENT AND NITRATES IN MINESOIL  

EPA Science Inventory

Samples of minesoils from 16- and 40-year-old mine spoil piles were analyzed in the laboratory for various chemical and physical properties to ascertain to what extent the material have been influenced by pedogenic processes during their relatively brief time of exposure. Nitrate...

379

Approximate prediction of melting point of nitramines, nitrate esters, nitrate salts and nitroaliphatics energetic compounds.  

PubMed

A simple new procedure is introduced to predict melting point of selected class of energetic compounds containing nitramines, nitrate esters, nitrate salts and nitroaliphatics energetic compounds. The number of nitrogen and oxygen as well as the number of nitramine group and the contribution of some specific functional groups would be needed in the new method. Energetic compounds should contain at least one of the functional groups including N-NO(2), C-ONO(2) or nonaromatic C-NO(2). Calculated melting point for 33 nitramines, nitrate esters, nitrate salt and nitroaliphatics are compared with experimental data. Predicted melting points have average deviation of 5.4% for these energetic compounds. PMID:16839681

Keshavarz, Mohammad Hossein

2006-12-01

380

Evidence for a plasma-membrane-bound nitrate reductase involved in nitrate uptake of Chlorella sorokiniana  

NASA Technical Reports Server (NTRS)

Anti-nitrate-reductase (NR) immunoglobulin-G (IgG) fragments inhibited nitrate uptake into Chlorella cells but had no affect on nitrate uptake. Intact anti-NR serum and preimmune IgG fragments had no affect on nitrate uptake. Membrane-associated NR was detected in plasma-membrane (PM) fractions isolated by aqueous two-phase partitioning. The PM-associated NR was not removed by sonicating PM vesicles in 500 mM NaCl and 1 mM ethylenediaminetetraacetic acid and represented up to 0.8% of the total Chlorella NR activity. The PM NR was solubilized by Triton X-100 and inactivated by Chlorella NR antiserum. Plasma-membrane NR was present in ammonium-grown Chlorella cells that completely lacked soluble NR activity. The subunit sizes of the PM and soluble NRs were 60 and 95 kDa, respectively, as determined by sodium-dodecyl-sulfate electrophoresis and western blotting.

Tischner, R.; Ward, M. R.; Huffaker, R. C.

1989-01-01

381

NITRATE DESTRUCTION LITERATURE SURVEY AND EVALUATION CRITERIA  

SciTech Connect

This report satisfies the initial phase of Task WP-2.3.4 Alternative Sodium Recovery Technology, Subtask 1; Develop Near-Tank Nitrate/Nitrite Destruction Technology. Some of the more common anions in carbon steel waste tanks at SRS and Hanford Site are nitrate which is corrosive, and nitrite and hydroxide which are corrosion inhibitors. At present it is necessary to periodically add large quantities of 50 wt% caustic to waste tanks. There are three primary reasons for this addition. First, when the contents of salt tanks are dissolved, sodium hydroxide preferentially dissolves and is removed. During the dissolution process the concentration of free hydroxide in the tank liquid can decrease from 9 M to less than 0.2 M. As a result, roughly half way through the dissolution process large quantities of sodium hydroxide must be added to the tank to comply with requirements for corrosion control. Second, hydroxide is continuously consumed by reaction with carbon dioxide which occurs naturally in purge air used to prevent buildup of hydrogen gas inside the tanks. The hydrogen is generated by radiolysis of water. Third, increasing the concentration of hydroxide increases solubility of some aluminum compounds, which is desirable in processing waste. A process that converts nitrate and nitrite to hydroxide would reduce certain costs. (1) Less caustic would be purchased. (2) Some of the aluminum solid compounds in the waste tanks would become more soluble so less mass of solids would be sent to High Level Vitrification and therefore it would be not be necessary to make as much expensive high level vitrified product. (3) Less mass of sodium would be fed to Saltstone at SRS or Low Level Vitrification at Hanford Site so it would not be necessary to make as much low level product. (4) At SRS less nitrite and nitrate would be sent to Defense Waste Processing Facility (DWPF) so less formic acid would be consumed there and less hydrogen gas would be generated. This task involves literature survey of technologies to perform the nitrate to hydroxide conversion, selection of the most promising technologies, preparation of a flowsheet and design of a system. The most promising technologies are electrochemical reduction of nitrates and chemical reduction with hydrogen or ammonia. The primary reviewed technologies are listed and they aredescribed in more detail later in the report: (1) Electrochemical destruction; (2) Chemical reduction with agents such as ammonia, hydrazine or hydrogen; (3) Hydrothermal reduction process; and (4) Calcination. Only three of the technologies on the list have been demonstrated to generate usable amounts of caustic; electrochemical reduction and chemical reduction with ammonia, hydrazine or hydrogen and hydrothermal reduction. Chemical reduction with an organic reactant such as formic acid generates carbon dioxide which reacts with caustic and is thus counterproductive. Treatment of nitrate with aluminum or other active metals generates a solid product. High temperature calcination has the potential to generate sodium oxide which may be hydrated to sodium hydroxide, but this is unproven. The following criteria were developed to evaluate the most suitable option. The numbers in brackets after the criteria are relative weighting factors to account for importance: (1) Personnel exposure to radiation for installation, routine operation and maintenance; (2) Non-radioactive safety issues; (3) Whether the technology generates caustic and how many moles of caustic are generated per mole of nitrate plus nitrite decomposed; (4) Whether the technology can handle nitrate and nitrite at the concentrations encountered in waste; (5) Maturity of technology; (6) Estimated annual cost of operation (labor, depreciation, materials, utilities); (7) Capital cost; (8) Selectivity to nitrogen as decomposition product (other products are flammable and/or toxic); (9) Impact of introduced species; (10) Selectivity for destruction of nitrate vs. nitrite; and (11) Cost of deactivation and demolition. Each technology was given a score from one

Steimke, J.

2011-02-01

382

Menaquinol-nitrate oxidoreductase of Bacillus halodenitrificans.  

PubMed

When grown anaerobically on nitrate-containing medium, Bacillus halodenitrificans exhibited a membrane-bound nitrate reductase (NR) that was solubilized by 2% Triton X-100 but not by 1% cholate or deoxycholate. Purification on columns of DE-52, hydroxylapatite, and Sephacryl S-300 yielded reduced methyl viologen NR (MVH-NR) with specific activities of 20 to 35 U/mg of protein that was stable when stored in 40% sucrose at -20 degrees C for 6 weeks. 3-[(3-cholamidopropyl)dimethylammonio]-2-hydroxypropone-1-sulfonat e (CHAPSO) and dodecyl-beta-D-maltoside stimulated enzyme activity three- to fourfold. Membrane extractions yielded purified NR that separated after electrophoresis into a 145-kDa alpha subunit, a 58-kDa beta subunit, and a 23-kDa gamma subunit. The electronic spectrum of dithionite-reduced, purified NR displayed peaks at 424.6, 527, and 557 nm, indicative of the presence of a cytochrome b, an interpretation consistent with the pyridine hemochrome spectrum formed. Analyses revealed a molybdenum-heme-non-heme iron ratio of 1:1:8 for the NR and the presence of molybdopterin. Electron paramagnetic resonance (EPR) signals characteristic of iron-sulfur centers were detected at low temperature. EPR also revealed a minor signal centered in the g = 2 region of the spectra. Upon reduction with dithionite, the enzyme displayed signals at g = 2.064, 2.026, 1.906, and 1.888, indicative of the presence of low-potential iron-sulfur centers, which resolve most probably as two [4Fe-4S]+1 clusters. With menadiol as the substrate for nitrate reduction, the Km for nitrate was 50-fold less than that seen when MVH was the electron donor. The cytochrome b557-containing enzyme from B. halodenitrificans is characterized as a menaquinol-nitrate:oxidoreductase. PMID:2013572

Ketchum, P A; Denariaz, G; LeGall, J; Payne, W J

1991-04-01

383

Menaquinol-nitrate oxidoreductase of Bacillus halodenitrificans.  

PubMed Central

When grown anaerobically on nitrate-containing medium, Bacillus halodenitrificans exhibited a membrane-bound nitrate reductase (NR) that was solubilized by 2% Triton X-100 but not by 1% cholate or deoxycholate. Purification on columns of DE-52, hydroxylapatite, and Sephacryl S-300 yielded reduced methyl viologen NR (MVH-NR) with specific activities of 20 to 35 U/mg of protein that was stable when stored in 40% sucrose at -20 degrees C for 6 weeks. 3-[(3-cholamidopropyl)dimethylammonio]-2-hydroxypropone-1-sulfonat e (CHAPSO) and dodecyl-beta-D-maltoside stimulated enzyme activity three- to fourfold. Membrane extractions yielded purified NR that separated after electrophoresis into a 145-kDa alpha subunit, a 58-kDa beta subunit, and a 23-kDa gamma subunit. The electronic spectrum of dithionite-reduced, purified NR displayed peaks at 424.6, 527, and 557 nm, indicative of the presence of a cytochrome b, an interpretation consistent with the pyridine hemochrome spectrum formed. Analyses revealed a molybdenum-heme-non-heme iron ratio of 1:1:8 for the NR and the presence of molybdopterin. Electron paramagnetic resonance (EPR) signals characteristic of iron-sulfur centers were detected at low temperature. EPR also revealed a minor signal centered in the g = 2 region of the spectra. Upon reduction with dithionite, the enzyme displayed signals at g = 2.064, 2.026, 1.906, and 1.888, indicative of the presence of low-potential iron-sulfur centers, which resolve most probably as two [4Fe-4S]+1 clusters. With menadiol as the substrate for nitrate reduction, the Km for nitrate was 50-fold less than that seen when MVH was the electron donor. The cytochrome b557-containing enzyme from B. halodenitrificans is characterized as a menaquinol-nitrate:oxidoreductase. Images

Ketchum, P A; Denariaz, G; LeGall, J; Payne, W J

1991-01-01

384

Molten nitrate salt technology development status report  

SciTech Connect

Recognizing thermal energy storage as potentially critical to the successful commercialization of solar thermal power systems, the Department of Energy (DOE) has established a comprehensive and aggressive thermal energy storage technology development program. Of the fluids proposed for heat transfer and energy storage molten nitrate salts offer significant economic advantages. The nitrate salt of most interest is a binary mixture of NaNO/sub 3/ and KNO/sub 3/. Although nitrate/nitrite mixtures have been used for decades as heat transfer and heat treatment fluids the use has been at temperatures of about 450/sup 0/C and lower. In solar thermal power systems the salts will experience a temperature range of 350 to 600/sup 0/C. Because central receiver applications place more rigorous demands and higher temperatures on nitrate salts a comprehensive experimental program has been developed to examine what effects, if any, the new demands and temperatures have on the salts. The experiments include corrosion testing, environmental cracking of containment materials, and determinations of physical properties and decomposition mechanisms. This report details the work done at Sandia National Laboratories in each area listed. In addition, summaries of the experimental programs at Oak Ridge National Laboratory, the University of New York, EIC Laboratories, Inc., and the Norwegian Institute of Technology on molten nitrate salts are given. Also discussed is how the experimental programs will influence the near-term central receiver programs such as utility repowering/industrial retrofit and cogeneration. The report is designed to provide easy access to the latest information and data on molten NaNO/sub 3//KNO/sub 3/ for the designers and engineers of future central receiver projects.

Carling, R.W.; Kramer, C.M.; Bradshaw, R.W.; Nissen, D.A.; Goods, S.H.; Mar, R.W.; Munford, J.W.; Karnowsky, M.M.; Biefeld, R.N.; Norem, N.J.

1981-03-01

385

Effect of Nitrate on Biogenic Sulfide Production  

PubMed Central

The addition of 59 mM nitrate inhibited biogenic sulfide production in dilute sewage sludge (10% [vol/vol]) amended with 20 mM sulfate and either acetate, glucose, or hydrogen as electron donors. Similar results were found when pond sediment or oil field brines served as the inoculum. Sulfide production was inhibited for periods of at least 6 months and was accompanied by the oxidation of resazurin from its colorless reduced state to its pink oxidized state. Lower amounts of nitrate (6 or 20 mM) and increased amounts of sewage sludge resulted in only transient inhibition of sulfide production. The addition of 156 mM sulfate to bottles with 59 mM nitrate and 10% (vol/vol) sewage sludge or pond sediment resulted in sulfide production. Nitrate, nitrite, and nitrous oxide were detected during periods where sulfide production was inhibited, whereas nitrate, nitrite, and nitrous oxide were below detectable levels at the time sulfide production began. The oxidation of resazurin was attributed to an increase in nitrous oxide which persisted in concentration of about 1.0 mM for up to 5 months. The numbers of sulfate-reducing organisms decreased from 106 CFU ml?1 sludge to less than detectable levels after prolonged incubation of oxidized bottles. The addition of 10 mM glucose to oxidized bottles after 14.5 weeks of incubation resulted in rereduction of the resazurin and subsequent sulfide production. The prolonged inhibition of sulfide production was attributed to an increase in oxidation-reduction potential due to biogenic production of nitrous oxide, which appeared to have a cytotoxic effect on sulfate-reducing populations.

Jenneman, Gary E.; McInerney, M. J.; Knapp, Roy M.

1986-01-01

386

Thermal analysis and temperature-programmed reduction studies of copper–zirconium and copper–zirconium–yttrium compounds  

Microsoft Academic Search

Differential thermal analysis evidenced that introduction of copper or yttrium into zirconia matrix delays its crystallization temperature. This result was connected to the stabilization of the zirconia tetragonal phase observed by X-ray diffraction. In addition, it was observed a decomposition delay of supported copper nitrate with yttrium content in a zirconia support. Temperature-programmed reduction revealed the existence of different copper

Madona Labaki; Jean-François Lamonier; Stéphane Siffert; Antoine Aboukaïs

2005-01-01

387

Praseodymium nitrate and neodymium nitrate complexation with organophosphorus reagents in supercritical carbon dioxide solvent  

Microsoft Academic Search

Complex formation reactions of praseodymium nitrate hexahydrate, and neodymium nitrate hexahydrate salts with tri-n-butyl phosphate (TBP) and several other neutral organophosphorus reagents were investigated in supercritical carbon dioxide. The concentration of the metal complexes in the supercritical fluid (SCF) phase was determined using UV-Vis and luminescence spectroscopies. The stoichiometry of the complexes was determined using the mole-ratio method. Extraction equilibrium

Robert V. Fox; R. Duane Ball; Peter de B. Harrington; Harry W. Rollins; John J. Jolley; Chien M. Wai

2004-01-01

388

Extraction of REE(III) Nitrates with Polymer-Supported Trialkylmethylammonium Nitrate  

Microsoft Academic Search

Extraction of La, Ce, Pr, Nd, Sm, and Y(III) nitrates with polymer-supported trialkylmethylammonium nitrate (Aliquat-336) in the presence 1-5 M NaNO3 in the aqueous phase is studied. The extraction isotherms are described taking into account formation of (R4N)2[Ln(NO3)5] in the extractant phase. The extraction constants decrease from La to Sm. The extraction constant of Y(III) is considerably lower than those

A. K. Pyartman; V. A. Keskinov; M. A. Mikhailenko; N. V. Nikitin; V. V. Lishchuk

2004-01-01

389

Amperometric nitrate biosensors on the basis of Pseudomonas stutzeri nitrate reductase  

Microsoft Academic Search

Microbial nitrate reductase from Pseudomonas stutzeri (NaR, EC 1.7.99.4) was tested in amperometric enzyme electrodes for detection of nitrate. The membrane-bound enzyme was coadsorbed with 19 different mediators onto graphite. We used the resulting sensors to characterize the bioelectrochemical properties of mediators of phenothiazine, triphenylmethane, sulfon–phthaleine and viologen types, and studied the dependence of the current densities on the electrode

D. Kirstein; L. Kirstein; F. Scheller; H. Borcherding; J. Ronnenberg; S. Diekmann; P. Steinrücke

1999-01-01

390

Silver Electrode Potentials in Alkali Nitrate and Nitrite Melts.  

National Technical Information Service (NTIS)

The correlation of the nitrate and nitrite systems through the use of a silver electrode is described. Consideration is also given to the use of a nitrate-nitrite solvent mixture and to the effect of changing the cation in the nitrate.

L. G. Boxall K. E. Johnson

1968-01-01

391

Chemistry of the Conversion of Nitrate Nitrogen to Smoke Products  

Microsoft Academic Search

NITRATE nitrogen has been of interest to us because of its natural occurrence in burley tobaccos and of its use as a tobacco additive. Sodium nitrate added to tobacco is known to reduce particulate matter, nicotine, phenol, and benzo(a)-pyrene in cigarette smoke1. It is thought that nitrates form oxygen and nitric oxide during smoking and thereby intercept radicals that would

W. R. Johnson; R. W. Hale; S. C. Clough; P. H. Chen

1973-01-01

392

Nitrate Reductase and Chlorate Toxicity in Chlorella vulgaris Beijerinck  

PubMed Central

A study of the growth-inhibiting effect of chlorate on the Berlin strain of Chlorella vulgaris Beijerinck provided complete confirmation of the theory of chlorate toxicity first proposed by Åberg in 1947. Chlorate was toxic to the cells growing on nitrate, and relatively nontoxic to the cells growing on ammonium. The latter cells contained only 0.01 as much NADH-nitrate reductase as the nitrate-grown cells. Chlorate could substitute for nitrate as a substrate of the purified nitrate reductase with Km = 1.2 mm, and Vmax = 0.9Vmax for nitrate. Bromate, and to a much smaller extent, iodate, also served as alternate substrates. Nitrate is a reversible competitive inhibitor of chlorate reduction, which accounts for the partial reversal, by high nitrate concentrations, of the observed inhibition of cell growth by chlorate. During the reduction of chlorate by NADH in the presence of purified nitrate reductase, there was a progressive, irreversible inhibition of the enzyme activity, presumably brought about by the reduction product, chlorite. Both the NADH-nitrate reductase activity and the associated NADH-cytochrome c reductase activity were inactivated to the same extent by added chlorite. The spectral properties of the cytochrome b557 associated with the purified enzyme were not affected by chlorite. The inactivation of the nitrate reductase by chlorite could account for the toxicity of chlorate to cells grown on nitrate, though the destruction of other cell components by chlorite or its decomposition products cannot be excluded.

Solomonson, L. P.; Vennesland, Birgit

1972-01-01

393

40 CFR 721.5769 - Mixture of nitrated alkylated phenols.  

Code of Federal Regulations, 2013 CFR

... false Mixture of nitrated alkylated phenols. 721.5769 Section 721.5769 ...5769 Mixture of nitrated alkylated phenols. (a) Chemical substance and significant...identified as a mixture of nitrated alkylated phenols (PMN P-93-987) is subject to...

2013-07-01

394

A model for nitrate distributions in oceanic oxygen minimum zones  

NASA Astrophysics Data System (ADS)

The vertical distributions of nitrate and nitrate deficit (nitrate consumed during denitrification) in oxygen minimum zones are modeled using a recycling mechanism incorporating bacterially mediated reaction and diffusion. At the core of the oxygen minimum zone bacteria reduce nitrate to nitrite and part of the nitrte to molecular nitrogen (denitrification). The remaining nitrite diffuses out of the layer, is oxidized to nitrate by nitrifying bacteria, and diffuses back into the layer to complete the cycle. The peak nitrite and nitrate deficit concentrations and the amount of recycling depend on two parameters: ?, the ratio of the sum of the nitrate and nitrate reduction rates to the diffusion coefficient, and ?, the ratio of the nitrate reduction rate to the sum of the nitrate and nitrite reduction rates. We estimate from peak concentrations that for oxygen minimum zones in the Arabian Sea, the eastern tropical North Pacific, and the coastal waters of Peru that the nitrogen production rate is between 39 and 60% of the nitrate reduction rate, with the difference in rates equaling the recycling rate between the denitrifying and nitrifying layers. A dependency of ? and ? on organic substrates available to denitrifying bacteria is suggested from independent chemostat studies and the primary productivity overlying the oxygen minimum zones. The peak concentrations of nitrite and nitrate deficit are near the mid-depth of the denitrifying layer, and from this characteristic we estimate the thickness of the denitrifying layers to be between 30 and 70% of the thickness of the oxygen minimum zones.

Anderson, James Jay; Okubo, Akira; Robbins, Alan S.; Richards, Francis A.

1982-09-01

395

21 CFR 176.320 - Sodium nitrate-urea complex.  

Code of Federal Regulations, 2013 CFR

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

2013-04-01

396

Titrimetric Determination of Thiocyanate in Solutions of the Hafnium-Zirconium Separation Process.  

National Technical Information Service (NTIS)

The control of the thiocyanate concentration is necessary during the process of separating hafnium from zirconium by the hexone-thiocyanate method. Said control is carried out by titrimetric determination of thiocyanate in aqueous and organic solutions co...

C. Vazquez M. Botbol M. H. Hernandez

1980-01-01

397

Study of zirconium/stainless steel interface in tubular junctions made by eutectic diffusion.  

National Technical Information Service (NTIS)

Reprocessing plants and pressurized water loops for fuels irradiation have zirconium (or zircaloy) and austenitic stainless steel tubes connected by mean of diffusion bondings. These bondings are achieved by producing an eutectic film at the interface bet...

J. Y. Blanc R. Le Goff P. Regnier

1990-01-01

398

The nitrate time bomb: a numerical way to investigate nitrate storage and lag time in the unsaturated zone.  

PubMed

Nitrate pollution in groundwater, which is mainly from agricultural activities, remains an international problem. It threatens the environment, economics and human health. There is a rising trend in nitrate concentrations in many UK groundwater bodies. Research has shown it can take decades for leached nitrate from the soil to discharge into groundwater and surface water due to the 'store' of nitrate and its potentially long travel time in the unsaturated and saturated zones. However, this time lag is rarely considered in current water nitrate management and policy development. The aim of this study was to develop a catchment-scale integrated numerical method to investigate the nitrate lag time in the groundwater system, and the Eden Valley, UK, was selected as a case study area. The method involves three models, namely the nitrate time bomb-a process-based model to simulate the nitrate transport in the unsaturated zone (USZ), GISGroundwater--a GISGroundwater flow model, and N-FM--a model to simulate the nitrate transport in the saturated zone. This study answers the scientific questions of when the nitrate currently in the groundwater was loaded into the unsaturated zones and eventually reached the water table; is the rising groundwater nitrate concentration in the study area caused by historic nitrate load; what caused the uneven distribution of groundwater nitrate concentration in the study area; and whether the historic peak nitrate loading has reached the water table in the area. The groundwater nitrate in the area was mainly from the 1980s to 2000s, whilst the groundwater nitrate in most of the source protection zones leached into the system during 1940s-1970s; the large and spatially variable thickness of the USZ is one of the major reasons for unevenly distributed groundwater nitrate concentrations in the study area; the peak nitrate loading around 1983 has affected most of the study area. For areas around the Bowscar, Beacon Edge, Low Plains, Nord Vue, Dale Springs, Gamblesby, Bankwood Springs, and Cliburn, the peak nitrate loading will arrive at the water table in the next 34 years; statistical analysis shows that 8.7 % of the Penrith Sandstone and 7.3 % of the St Bees Sandstone have not been affected by peak nitrate. This research can improve the scientific understanding of nitrate processes in the groundwater system and support the effective management of groundwater nitrate pollution for the study area. With a limited number of parameters, the method and models developed in this study are readily transferable to other areas. PMID:23801341

Wang, L; Butcher, A S; Stuart, M E; Gooddy, D C; Bloomfield, J P

2013-10-01

399

Long-term leaching behaviour of glasses containing zirconium  

NASA Astrophysics Data System (ADS)

Five borosilicate glasses containing up to 20% zirconium oxide and 10% non-radioactive fission products or lanthanum oxide (which simulates the behaviour of the actinides) were leached in stagnant distilled water at 20 ° C for 2 years. The leaching rates of Na, La, Mn, Cs and Mo varied with time and the chemical composition of the glass from 0.7 to 12, 0.006 to 0.14, 0.8 to 1.2, 0.4 to 0.8 and 8 to 25 mg/m 2/d respectively. The glasses which showed the beast short-term resistance do not have the best long-term resistance.

St.-Pierre, Jean; Zikovsky, L.

1984-08-01

400

Titanium-Zirconium-Nickel Alloy Inside Marshall's Electrostatic Levitator (ESL)  

NASA Technical Reports Server (NTRS)

This Photo, which appeared on the July cover of `Physics Today', is of the Electrostatic Levitator (ESL) at NASA's Marshall Space Flight Center (MSFC). The ESL uses static electricity to suspend an object (about 3-4 mm in diameter) inside a vacuum chamber allowing scientists to record a wide range of physical properties without the sample contracting the container or any instruments, conditions that would alter the readings. Once inside the chamber, a laser heats the sample until it melts. The laser is then turned off and the sample cools, changing from a liquid drop to a solid sphere. In this particular shot, the ESL contains a solid metal sample of titanium-zirconium-nickel alloy. Since 1977, the ESL has been used at MSFC to study the characteristics of new metals, ceramics, and glass compounds. Materials created as a result of these tests include new optical materials, special metallic glasses, and spacecraft components.

2003-01-01

401

Titanium-Zirconium-Nickel Alloy Inside Marshall's Electrostatic Levitator (ESL)  

NASA Technical Reports Server (NTRS)

This is a close-up of a sample of titanium-zirconium-nickel alloy inside the Electrostatic Levitator (ESL) vacuum chamber at NASA's Marshall Space Flight Center (MSFC). The ESL uses static electricity to suspend an object (about 3-4 mm in diameter) inside a vacuum chamber allowing scientists to record a wide range of physical properties without the sample contracting the container or any instruments, conditions that would alter the readings. Once inside the chamber, a laser heats the sample until it melts. The laser is then turned off and the sample cools, changing from a liquid drop to a solid sphere. Since 1977, the ESL has been used at MSFC to study the characteristics of new metals, ceramics, and glass compounds. Materials created as a result of these tests include new optical materials, special metallic glasses, and spacecraft components.

2003-01-01

402

Crystal structure of potassium titanyl phosphate doped with zirconium  

SciTech Connect

This paper reports on the results of precision X-ray structural investigations of single crystals of the compounds KTi{sub 0.96}Zr{sub 0.04}OPO{sub 4} (at 293 K) and KTi{sub 0.97}Zr{sub 0.03}OPO{sub 4} (at 293 and 105 K). No significant splitting of the positions occupied by potassium atoms is revealed. This result is in agreement with a considerable decrease in the electrical conductivity of potassium titanyl phosphate KTiOPO{sub 4} (KTP) crystals doped with zirconium (KTP: Zr) as compared to crystals of undoped potassium titanyl phosphate. It is established that the difference between the Ti-O bond lengths in chains formed by titanium octahedra is not a single structural parameter responsible for the nonlinear optical properties of crystals in this series.

Alekseeva, O. A., E-mail: olalex@ns.crys.ras.ru; Dudka, A. P.; Sorokina, N. I. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation); Pietraszko, A. [Polish Academy of Sciences, Institute of Low Temperature and Structure Research (Poland); Rabadanov, M. Kh. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation); Agapova, E. I.; Voronkova, V. I. [Lomonosov Moscow State University (Russian Federation); Simonov, V. I. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation)

2007-07-15

403

Extraction and spectrophotometric determination of zirconium(IV)  

SciTech Connect

A sensitive and selective method for the extraction and spectrophotometric determination of Zr(IV) with N-p-chlorophenyl-3,4,5-trimethoxycinnamohydroxamic acid (PTCHA) has been developed. The binary complex of Zr(IV)-PTCHA is extracted from 2-6 M HCl into chloroform, having a maximum absorbance at 385 nm; molar absorptivity 2.1 x 10/sup 4/ 1 mol/sup -1/ cm/sup -1/. A ternary complex with xylenol orange (Zr-PTCHA-XO) have been studied in chloroform-ethanol media, which absorbs at 540 nm; molar absorptivity 4.3 x 10/sup 4/ 1 mol/sup -1/ cm /sup -1/. The present method is applied for the analysis of zirconium in standard samples. 15 references, 3 tables.

Agrawal, Y.K.; John, K.T.

1984-01-01

404

Characterization of hemoglobin immobilized on gamma-zirconium phosphate.  

PubMed

The fact that different gamma-zirconium phosphate (gamma-ZrP) preintercalation method induced varied degree and type of conformational change of the adsorption protein was confirmed by characterization techniques including circular dichroism (CD), fourier transform infrared spectroscopy (FTIR) and X-ray powder diffraction (XRD) analysis. The results indicated that the association of hemoglobin with gamma-ZrP preintercalated using butylamine was correlated with conformational change in the secondary structure of the protein. gamma-ZrP which was preintercalated with tetra (n-butylammonium) hydroxide caused the conformational change of Hemoglobin in both the secondary structure and the tertiary structure. X-ray powder diffraction analysis was used to analyze the crystalline structure of the nanocomposites prepared by relamination. The adsorption isotherms of Hemoglobin on different matrices were set up and fitted with Langmuir and Freundlich equations. PMID:15261062

Geng, LiNa; Wang, Xu; Li, Na; Xiang, MingHui; Li, Ke'an

2004-04-15

405

Niobium-Zirconium Chronometry and Early Solar System Development  

NASA Astrophysics Data System (ADS)

Niobium-92 (92Nb) decays to zirconium-92 (92Zr) with a half-life of 36 million years and can be used to place constraints on the site of p-process nucleosynthesis and the timing of early solar system processes. Recent results have suggested that the initial 92Nb/93Nb of the solar system was high (>10-3). We report Nb-Zr internal isochrons for the ordinary chondrite Estacado (H6) and a clast of the mesosiderite Vaca Muerta, both of which define an initial 92Nb/93Nb ratio of ~10-5. Therefore, the solar system appears to have started with a ratio of <3 × 10-5, which implies that Earth's initial differentiation need not have been as protracted as recently suggested.

Schönbächler, Maria; Rehkämper, Mark; Halliday, Alex N.; Lee, Der-Chuen; Bourot-Denise, Michèle; Zanda, Brigitte; Hattendorf, Bodo; Günther, Detlef

2002-03-01

406

Improved tribology of tool steel by zirconium ion implantation  

SciTech Connect

AISI D3 tool steel was ion implanted with zirconium and the improvement in surface tribological properties investigated. The Zr ion implantation was done using a metal vapor vacuum arc broad-beam ion source, with a mean ion energy of 130 keV and at doses of 3.6 x 10(sup 16), 5 x 10(sup 16) and 1 x 10(sup 17) ions/cm2. Wear, friction and hardness of the implanted samples were measured and compared to the performance of unimplanted steel. The wear resistance was increased by about a factor of two, the friction remained about the same or was possibly increased by a small amount, and the hardness was improved by a factor of five or more by the ion implantation. We also investigated the effect on the Zr implantation profile of the multi-component energy distribution of the ion beam used here.

Akbas, N.; Oztarhan, A.; Monteiro, O.R.; Brown, I.G.

2001-02-01

407

Study of nitrogen-rich titanium and zirconium nitride films  

SciTech Connect

Thin titanium nitride (TiN) and zirconium nitride (ZrN) films containing excess nitrogen up to 59 and 63 at. % N, respectively, were deposited on austenitic stainless-steel substrates by reactive triode ion plating at about 823 K. The film structure and surface chemistry were studied using x-ray diffraction, scanning Auger spectroscopy, and electron energy-loss spectroscopy (EELS). In TiN films only the face-centered-cubic mononitride phase was detected. The lattice parameter of the stoichiometric TiN film was larger than the corresponding bulk value and it increased with increasing nitrogen content. The lattice parameter of overstoichiometric ZrN films showed abnormal behavior when calculated from different diffracting planes. This behavior together with the EELS and other measurements indicate that a dielectric Zr/sub 3/N/sub 4/ phase was formed at overstoichiometric compositions.

Ristolainen, E.O.; Molarius, J.M.; Korhonen, A.S.; Lindroos, V.K.

1987-07-01

408

Cavitation at triple nodes in {alpha}-zirconium polycrystals  

SciTech Connect

The damage mechanisms of {alpha}-zirconium polycrystals in tension at room temperature and their dependence on texture and grain size are investigated. Ductile damage proceeds by growth of cavities appearing at triple nodes; at larger strain, other cavities nucleate at precipitate platelets. The cavitation kinetics depend on the tension direction; they are lower the coarser the grains. For a better understanding of the cavity formation at triple nodes, the internal stress field due to intergranular plastic incompatibility is estimated. The mean stress exhibits a logarithmic singularity on the triple junction. By combining this property with some experimentally determined features of the cavity growth (tubular shape along the c axis and growth by activation of prismatic glide), a crystallographic orientation-dependent cavitation criterion is derived. The determination of the grains orientation by the E.B.S.D. technique leads to a satisfactory comparison of the model predictions with the observations.

Care, S.; Zaoui, A. [Ecole Polytechnique, Palaiseau (France). Lab. de Mecanique des Solides] [Ecole Polytechnique, Palaiseau (France). Lab. de Mecanique des Solides

1996-04-01

409

Structure and electronic properties of zirconium and hafnium nitrides and oxynitrides  

Microsoft Academic Search

The atomic structure, stability and electronic properties of zirconium and hafnium nitrides and oxynitrides (MN, M3N4, and M2N2O; M=Zr, Hf) have been studied using first-principles density functional theory calculations. It is found that the orthorhombic Pnam structure of M3N4, which was observed experimentally for zirconium nitride, is more stable for this stoichiometry than the cubic spinel and rock-salt-type structures. The

D. I. Bazhanov; A. A. Knizhnik; A. A. Safonov; A. A. Bagatur'yants; M. W. Stoker; A. A. Korkin

2005-01-01

410

Co-Rolled U10Mo/Zirconium-Barrier-Layer Monolithic Fuel Foil Fabrication Process  

SciTech Connect

Integral to the current UMo fuel foil processing scheme being developed at Idaho National Laboratory (INL) is the incorporation of a zirconium barrier layer for the purpose of controlling UMo-Al interdiffusion at the fuel-meat/cladding interface. A hot “co-rolling” process is employed to establish a ~25-µm-thick zirconium barrier layer on each face of the ~0.3-mm-thick U10Mo fuel foil.

G. A. Moore; M. C. Marshall

2010-01-01

411

DELAYED FAILURE HYDROGEN EMBRITTLEMENT OF ZIRCONIUM. Quarterly Report No. 3, March 15, 1962June 14, 1962  

Microsoft Academic Search

An investigation was made to determine the extent to which zirconium and ;\\u000a zirconium alloys exhibit delayed failure (static fatigue) as caused by a ;\\u000a combination of absorbed hydrogen and applied stress. Evaluation of ;\\u000a susceptibility to time-dependent fracture was performed on an experimental Zr-- ;\\u000a Al-- Sn-- Mo alloy containing 500 ppm hydrogen and the Canadian Zr-2.5Nb cladding ;

D. Weinstein; F. C. Holtz

1962-01-01

412

Mesoporous Zirconium Titanium Oxides. Part 2: Synthesis, Porosity, and Adsorption Properties of Beads  

Microsoft Academic Search

Mesoporous zirconium titanium mixed-oxide beads having disordered wormhole textures and mole fractions of Zr (x) ranging from x = 0.25 to 0.67 have been prepared. The bead preparation method combined the forced hydrolysis of mixtures of zirconium-titanium alkoxides in the presence of long-chain carboxylates with external gelation. Uniformly sized beads could be produced in the size range 0.5--1.1 mm by

G. Devlet Sizgek; Erden Sizgek; Christopher S. Griffith; Vittorio Luca

2009-01-01

413

Ultrafine microsphere particles of zirconium titanate produced by homogeneous dielectric-tuning coprecipitation  

Microsoft Academic Search

Zirconium titanates are widely used in electrical (common microwave dielectrics) and optical devices as well as in bifunctional catalysis and structural ceramics. In this paper, ultrafine amorphous solid microsphere precursor particles of zirconium titanate (ZrxTi1 - xO2) with possibly tailored intraparticle nanostructure (i.e., nanosized pores) were synthesized by a “dielectric-tuning” solution coprecipitation method, in which inorganic salts were dissolved in

Michael Z.-C. Hu; E. A. Payzant; K. R. Booth; C. J. Rawn; R. D. Hunt; L. F. Allard

2003-01-01

414

Solvent Extraction Separation of Zirconium (iv) With Anberlite LA - 1 From Citrate Solutions  

Microsoft Academic Search

Zirconium was quantitatively extracted with 8 × 10 M of Amberlite LA-1 or LA-2 xylene from 0.001 M citric acid at pH 3.5 and it was stripped from the organic phase with 2 M hydrochloric acid and was determined spectrophotometrically at 665 nm as its complex with arsenazo III. Zirconium was separated from binary as well as tertiary mixtures by

C. P. Vibhute; S. M. Khopkar

1983-01-01

415

Features of Preparing Nano-Size Powders of Tetragonal Zirconium Dioxide Stabilized with Yttrium  

Microsoft Academic Search

The effect of wet chemical synthesis parameters on the properties of nano-powders of zirconium dioxide stabilized with yttrium is studied. Features of nano-powder synthesis by the oxalate, hydroxide and thermal hydrolysis of a sol methods are determined. Nano-size zirconium dioxide powder stabilized with 3 mole% yttrium is prepared by hydrothermal coprecipitation from a sol of metal chlorides and urea followed

O. O. Vasylkiv; Y. Sakka; V. V. Skorokhod

2005-01-01

416

Continued Investigation of the Solid-Solid Phase Transitions in Zirconium  

NASA Astrophysics Data System (ADS)

Work has continued to refine and investigate differences in the Hugoniots for Zirconium with differing impurity levels. Past work has shown that interstitial oxygen inhibits the ?->? phase transition but appears to have little effect on the ?->? phase transition. Further plate impact experiments have been carried out to determine differences in the Hugoniots for two of the three types of Zirconium samples studied in previous work.

Rigg, P. A.; Greeff, C. W.; Gray, G. T., III

2011-06-01

417

A novel solid-phase extraction method for separation and preconcentration of zirconium  

Microsoft Academic Search

This work assesses the use of modified natural clinoptilolite as an adsorptive material for separation and preconcentration\\u000a of trace amounts of zirconium ions. A simple, rapid and economical method was developed for the preconcentration of trace\\u000a amounts of zirconium in aqueous medium using 1-(2-pyridylazo)-2-naphthol as a complexing agent. Effect of sample pH, flow\\u000a rate of sample and elution solutions, breakthrough

Hossein Faghihian; Mahboobeh Kabiri-Tadi

2010-01-01

418

Predicting Peri-implant Stresses Around Titanium and Zirconium Dental Implants-A Finite Element Analysis.  

PubMed

Due to anatomical and surgical constrains the implant placement may not be parallel to each other always. Non-parallel implants are subjected to detrimental stresses at implant bone interface. Also depending on type of implant material i.e. titanium or zirconium, stresses tend to vary due to change in physical and mechanical properties. Hence stress analysis at implant bone interface between different parallel and non-parallel implants becomes significant. Evaluation and comparison of stress distribution in the bone around two parallel and non-parallel titanium and zirconium dental implants on axial and non-axial loading supporting three unit fixed prosthesis. Three dimensional finite element models (M1, M2, M3) were made of three differently angulated implants in ANSYS (11.0 Version) software and P4 processor with a speed of 3 GHz and 3 Gb RAM hardware, common for titanium and zirconium implants. Stress around the implants was analyzed on an axial load of 200 N and a non-axial load of 50 N. In both titanium and zirconium implants on axial loading in cortical bone, higher stresses were observed in M3 followed by M2 and M1. On non-axial loading higher stresses were observed in M2, followed by M3 and M1. In both titanium and zirconium implants on axial and non-axial loading in cancellous bone stresses were higher in M3 followed by M2 and M1. Zirconium implants showed lower stresses in cortical bone and higher stresses in cancellous bone compared to titanium implants. Over all Stresses in the bone were more due to titanium implants than zirconium implants. Zirconium implants led to lower peri-implant stresses than titanium implants. PMID:24431734

Gujjarlapudi, Manmohan Choudary; Nunna, Narayana Venkata; Manne, Sanjay Dutt; Sarikonda, Varalakshmi Reddy; Madineni, Praveen Kumar; Meruva, Reddi Narasimha Rao

2013-09-01

419

Porosity occurring in modification of hypoeutectic silumins with strontium and zirconium  

SciTech Connect

The authors investigate modifications in castability, temperature effects, porosity, and fracture properties in silicon-aluminium alloys after being alloyed with strontium and zirconium. The porosity observed in alloys containing strontium was found to have a microshrinkage character. Alloying with zirconium was found to reduce somewhat the tendency of the alloy toward the formation of microshrinkage porosity but did not compensate for the influence of strontium.

Kutsenok, N.L.; Ganiev, I.N.; Yanchuk, V.N.

1987-07-01

420

Roles of nitrate, nitrite and ammonium ion in phytochrome regulation of nitrate reductase gene expression in maize  

Microsoft Academic Search

Abbreviations: 5HT, 5-hydroxytryptamine; NR, nitrate reductase; NiR, nitrite reductase; PER phospho enol pyruvate; Pfr, phytochrome; PI, phosphoinositude(s); PKC, protein ldnase C; PMA, phorbol myristate acetate SUMMARY The influence of nitrate and its metabolites on the nitrate reductase (NR) gene expression and its relationship with phytochrome (Pfr) regulation of NR in etiolated maize leaves is examined. Nitrate inSuction and Pfr stimulation

Nandula Raghuram I; Sudhir K. Sopory

1999-01-01

421

Identification of an assimilatory nitrate reductase in mutants of Paracoccus denitrificans GB17 deficient in nitrate respiration  

Microsoft Academic Search

A Paracoccus denitrificans strain (M6?) unable to use nitrate as a terminal electron acceptor was constructed by insertional inactivation of the periplasmic\\u000a and membrane-bound nitrate reductases. The mutant strain was able to grow aerobically with nitrate as the sole nitrogen source.\\u000a It also grew anaerobically with nitrate as sole nitrogen source when nitrous oxide was provided as a respiratory electron

Heather J. Sears; Phillip J. Little; David J. Richardson; Ben C. Berks; Stephen Spiro; Stuart J. Ferguson

1997-01-01

422

Ion beam mixing of chromium or zirconium films with sapphire  

SciTech Connect

Ion beam mixing of thin metallic films deposited on sapphire substrates was studied for chromium or zirconium films deposited on single crystalline {alpha}-Al{sub 2}0{sub 3} substrates. Evidence for the influence of equilibrium thermodynamic factors was sought by comparing the effects of bombarding with oxygen ions (300 and 1073 K) with those of neon ions (300 K). Thermodynamic calculations indicate that mixing might occur for Zr/sapphire at 1073 K but not at 300 K. Chromium/sapphire should not be mixed at either temperature. The implantation energy placed the peak oxygen concentration at the metal/sapphire interface in an attempt to maintain an equilibrium ratio of cations/anions and promote a radiation-induced chemical reaction across the interface. Rutherford backscattering-ion channeling measurements indicated that the widths of ``mixed`` regions were consistent with those predicted from ballistic considerations. Other experiments employed a heavier ion (krypton) as the mixing ion (300 K) in order to increase the mixing efficiency. Rutherford backscattering-ion channeling and x-ray photoelectron spectroscopy were used to determine the extent and nature of any interface modification. XPS results indicated that only metallic chromium (Cr{sup 0}) was present near the interface before and after irradiation with Kr at 300 K. Zirconium exhibited only the metallic state (Zr{sup 0}) in the as-deposited film but was present as both Zr{sup 0} and Zr{sup 4{plus}} after irradiation. Some metallic aluminum (AI{sup O}) was detected near the Zr/sapphire interface, suggesting that a local chemical reaction between Zr and the sapphire occurred during bombardment. No long-range material transport was detected for any experimental condition examined; the width of the ``mixed` region in each case was consistent with that expected for ballistic effects.

McHargue, C.J. [Tennessee Univ., Knoxville, TN (United States); Joslin, D.L.; White, C.W. [Oak Ridge National Lab., TN (United States); daSilva, M.F.; Alves, E. [National Inst. for Industrial Technology and Engineering, Sacavem (Portugal); Soares, J.C. [Lisbon Univ. (Portugal)

1995-12-31

423

Genetic basis for nitrate resistance in Desulfovibrio strains  

PubMed Central

Nitrate is an inhibitor of sulfate-reducing bacteria (SRB). In petroleum production sites, amendments of nitrate and nitrite are used to prevent SRB production of sulfide that causes souring of oil wells. A better understanding of nitrate stress responses in the model SRB, Desulfovibrio vulgaris Hildenborough and Desulfovibrio alaskensis G20, will strengthen predictions of environmental outcomes of nitrate application. Nitrate inhibition of SRB has historically been considered to result from the generation of small amounts of nitrite, to which SRB are quite sensitive. Here we explored the possibility that nitrate might inhibit SRB by a mechanism other than through nitrite inhibition. We found that nitrate-stressed D. vulgaris cultures grown in lactate-sulfate conditions eventually grew in the presence of high concentrations of nitrate, and their resistance continued through several subcultures. Nitrate consumption was not detected over the course of the experiment, suggesting adaptation to nitrate. With high-throughput genetic approaches employing TnLE-seq for D. vulgaris and a pooled mutant library of D. alaskensis, we determined the fitness of many transposon mutants of both organisms in nitrate stress conditions. We found that several mutants, including homologs present in both strains, had a greatly increased ability to grow in the presence of nitrate but not nitrite. The mutated genes conferring nitrate resistance included the gene encoding the putative Rex transcriptional regulator (DVU0916/Dde_2702), as well as a cluster of genes (DVU0251-DVU0245/Dde_0597-Dde_0605) that is poorly annotated. Follow-up studies with individual D. vulgaris transposon and deletion mutants confirmed high-throughput results. We conclude that, in D. vulgaris and D. alaskensis, nitrate resistance in wild-type cultures is likely conferred by spontaneous mutations. Furthermore, the mechanisms that confer nitrate resistance may be different from those that confer nitrite resistance.

Korte, Hannah L.; Fels, Samuel R.; Christensen, Geoff A.; Price, Morgan N.; Kuehl, Jennifer V.; Zane, Grant M.; Deutschbauer, Adam M.; Arkin, Adam P.; Wall, Judy D.

2014-01-01

424

Nitrate leaching in an Atlantic Coastal Plain soil amended with poultry manure or urea-ammonium nitrate: Influence of thiosulfate  

Microsoft Academic Search

Nitrate leaching, which can lead to groundwater contamination, is a common occurrence, especially in sandy, well drained soils. Nitrogen from poultry manure (PM) and ammonium fertilizers has been shown to undergo rapid nitrification upon addition to soils, making it highly susceptible to nitrate leaching. Any management technique that could delay nitrification and thereby reduce nitrate leaching would be desirable. Ammonium

Y. E. Sallade; J. T. Sims

1994-01-01

425

Mechanical resistance of zirconium implant abutments: A review of the literature  

PubMed Central

The increase of aesthetic demands, together with the successful outcome of current implants, has renewed interest in the search for new materials with enough mechanical properties and better aesthetic qualities than the materials customarily used in implanto-prosthetic rehabilitation. Among these materials, zirconium has been used in different types of implants, including prosthetic abutments. The aim of the present review is to analyse current scientific evidence supporting the use of this material for the above mentioned purposes. We carried out the review of the literature published in the last ten years (2000 through 2010) of in vitro trials of dynamic and static loading of zirconium abutments found in the databases of Medline and Cochrane using the key words zirconium abutment, fracture resistance, fracture strength, cyclic loading. Although we have found a wide variability of values among the different studies, abutments show favourable clinical behaviour for the rehabilitation of single implants in the anterior area. Such variability may be explained by the difficulty to simulate daily mastication under in vitro conditions. The clinical evidence, as found in our study, does not recommend the use of implanto-prosthetic zirconium abutments in the molar area. Key words: Zirconium abutment, zirconium implant abutment, zirconia abutment, fracture resistance, fracture strength, cyclic loading.

Vaquero-Aguilar, Cristina; Torres-Lagares, Daniel; Jimenez-Melendo, Manuel; Gutierrez-Perez, Jose L.

2012-01-01

426

Nitrate input/output budget and nitrate isotope ratio in forest ecosystems.  

NASA Astrophysics Data System (ADS)

Recent years nitrogen input to forest has been increased by industrial development and increase use of fossil fuel, so elucidating the fate of nitrate added to forest ecosystems is quite important issue for revealing its potential of nitrogen-removing from environment, and better management of forests. Forest ecosystems in mountains region, typically in Japan, vary in many respects from Europe or United States, therefore, It is not possible to make the research result of Europe and America simply adjust to Japan as it is. In this study, measurement of nitrogen and oxygen isotopic ratios of nitrate give us integrated information of nitrate dynamics in Japanese forest ecosystems. There are cedar/ cypress plantations in Japan, about 40 percent of the total forest area is, need to maintain, therefore forest disturbance by human activity (e.g. clearcutting or thinning) is large proportion of total forest ecosystems. Forest disturbance is considered to affect nitrate discharge in many ways (Aber et al. 1998), and contribution of atmospheric nitrate to total nitrate discharge is dramatically increased after disturbance (e.g. forest decline by acid rain: Durka et al. 1994). In our study site with different application (logging) history, nitrate concentrations in streamwater showed clear trend. Atmospheric nitrate has high oxygen isotope ratio (over 10 per-mill vs. VSMOW), while its nitrogen isotopic ratio is about 0 per-mill vs. Atmosphere N2 and nitrate undergone denitrification in soil has high nitrogen isotope ratio (Kendall 1998). Nitrate discharge from forest ecosystems is mainly regulated by plant/microbe uptake, nitrification (NH4 toNO3) and denitrification (NO3 to N2). If clear cut of plantation affects the ratio of atmospheric versus microbial (nitrified) nitrate in streamwater, together with high concentrations in younger forest, we can assume several signal of isotopic ratios of nitrate with the hypothesis below; 1) Streamwater from young forests has high oxygen isotope ratio resemble to that of rain. 2) Streamwater from aged forests has rather lower oxygen isotope ratio than young. 3) Nitrogen isotope ratio is affected by many parameter, groundwater level, angle of dip, watershed area, soil composition, and so on. In this study site, we can comparable of the difference of the nitrogen circulation when "year after re- foretasting" is assumed to be the main parameter under almost the same environmental condition. Therefore, it is thought that "year " is an element that rules the nitrogen circulation if a significant difference is seen on this site compared with the nitrate isotope ratios. In this research, it is assumed to be a purpose to analyze how the nitrogen circulation in the forest ecosystem is characterized by 100-year-timescale. We inspect this hypothesis and make first step of forest assessment by nitrate stable isotope ratios.

Tobari, Y.; Koba, K.; Fukushima, K.; Tokuchi, N.; Tateno, R.; Ohte, N.; Suzuki, N.; Toyoda, S.; Yoshida, N.

2006-12-01

427

Factors influencing protein tyrosine nitration - structure-based predictive models  

PubMed Central

Models for exploring tyrosine nitration in proteins have been created based on 3D structural features of 20 proteins for which high resolution X-ray crystallographic or NMR data are available and for which nitration of 35 total tyrosines has been experimentally proven under oxidative stress. Factors suggested in previous work to enhance nitration were examined with quantitative structural descriptors. The role of neighboring acidic and basic residues is complex: for the majority of tyrosines that are nitrated the distance to the heteroatom of the closest charged sidechain corresponds to the distance needed for suspected nitrating species to form hydrogen bond bridges between the tyrosine and that charged amino acid. This suggests that such bridges play a very important role in tyrosine nitration. Nitration is generally hindered for tyrosines that are buried and for those tyrosines where there is insufficient space for the nitro group. For in vitro nitration, closed environments with nearby heteroatoms or unsaturated centers that can stabilize radicals are somewhat favored. Four quantitative structure-based models, depending on the conditions of nitration, have been developed for predicting site-specific tyrosine nitration. The best model, relevant for both in vitro and in vivo cases predicts 30 of 35 tyrosine nitrations (positive predictive value) and has a sensitivity of 60/71 (11 false positives).

Bayden, Alexander S.; Yakovlev, Vasily A.; Graves, Paul R.; Mikkelsen, Ross B.; Kellogg, Glen E.

2010-01-01

428

Nitrate loss in Saylorville Lake reservoir in Iowa  

NASA Astrophysics Data System (ADS)

Few studies have quantified nitrate-nitrogen reductions in rivers flowing through large flood control reservoirs despite their potential role in helping to meet nitrate-N load reduction targets. In this study, we evaluated a 26-year record of nitrate-N monitoring in Saylorville Lake reservoir that impounds the Des Moines River in central Iowa to estimate the annual mass of nitrate-N removed and evaluate controls on inter-annual patterns of nitrate-N removal rates. Results from mass balance calculations indicate a nitrate mass loss of 4.9% over the 26 year period from 1986 through 2011. The annual percent nitrate mass removed is related to hydraulic loading rate with low flow years having longer retention times removing a significantly greater percentage of nitrate than is removed during high flow years with low retention times. Average annual residence times varied from 3.5 to 74 days with a 26 year average of 9.7 days. Nitrate removal results for Saylorville Lake agree well with published work for several other reservoirs which together encompass a broad range of nitrate removal rates. Combining data from Saylorville Lake with other published studies, a relationship between nitrate-N removal rate and hydraulic loading rate was developed resulting in a predictive equation with a model R2 = 0.92.

Stenback, Greg A.; Crumpton, William G.; Schilling, Keith E.

2014-05-01

429

Thermal decomposition hazard evaluation of hydroxylamine nitrate.  

PubMed

Hydroxylamine nitrate (HAN) is an important member of the hydroxylamine family and it is a liquid propellant when combined with alkylammonium nitrate fuel in an aqueous solution. Low concentrations of HAN are used primarily in the nuclear industry as a reductant in nuclear material processing and for decontamination of equipment. Also, HAN has been involved in several incidents because of its instability and autocatalytic decomposition behavior. This paper presents calorimetric measurement for the thermal decomposition of 24 mass% HAN/water. Gas phase enthalpy of formation of HAN is calculated using both semi-empirical methods with MOPAC and high-level quantum chemical methods of Gaussian 03. CHETAH is used to estimate the energy release potential of HAN. A Reactive System Screening Tool (RSST) and an Automatic Pressure Tracking Adiabatic Calorimeter (APTAC) are used to characterize thermal decomposition of HAN and to provide guidance about safe conditions for handling and storing of HAN. PMID:16154263

Wei, Chunyang; Rogers, William J; Mannan, M Sam

2006-03-17

430

Photolysis of alkaline-earth nitrates  

NASA Astrophysics Data System (ADS)

Peroxynitrite and nitrite ions are the diamagnetic products of photolysis (with light at a wavelength of 253.7 nm) of alkaline-earth nitrates; the paramagnetic products and hydrogen peroxide were not found. The structural water in alkaline-earth nitrate crystals did not affect the qualitative composition of the photodecomposition products. The quantum yield of nitrite ions was 0.0012, 0.0038, 0.0078, and 0.0091 quanta-1 and that of peroxynitrite ions was 0.0070, 0.0107, 0.0286, and 0.0407 quanta-1 for Sr(NO3)2, Ba(NO3)2, Ca(NO3)2 · 4H2O, and Mg(NO3)2 · 6H2O, respectively.

Kriger, L. D.; Miklin, M. B.; Dyagileva, E. P.; Anan'ev, V. A.

2013-02-01

431

Investigation of tyrosine nitration in proteins by mass spectrometry.  

PubMed

In vivo nitration of tyrosine residues is a post-translational modification mediated by peroxynitrite that may be involved in a number of diseases. The aim of this study was to evaluate possibilities for site-specific detection of tyrosine nitration by mass spectrometry. Angiotensin II and bovine serum albumin (BSA) nitrated with tetranitromethane (TNM) were used as model compounds. Three strategies were investigated: (i) analysis of single peptides and protein digests by matrix-assisted laser desorption/ionization (MALDI) peptide mass mapping, (ii) peptide mass mapping by electrospray ionization (ESI) mass spectrometry and (iii) screening for nitration by selective detection of the immonium ion of nitrotyrosine by precursor ion scanning with subsequent sequencing of the modified peptides. The MALDI time-of-flight mass spectrum of nitrated angiotensin II showed an unexpected prompt fragmentation involving the nitro group, in contrast to ESI-MS, where no fragmentation of nitrated angiotensin II was observed. The ESI mass spectra showed that mono- and dinitrated angiotensin II were obtained after treatment with TNM. ESI-MS/MS revealed that the mononitrated angiotensin II was nitrated on the side-chain of tyrosine. The dinitrated angiotensin II contained two nitro groups on the tyrosine residue. Nitration of BSA was confirmed by Western blotting with an antibody against nitrotyrosine and the sites for nitration were investigated by peptide mass mapping after in-gel digestion. Direct mass mapping by ESI revealed that two peptides were nitrated. Precursor ion scanning for the immonium ion for nitrotyrosine revealed two additional partially nitrated peptides. Based on the studies with the two model compounds, we suggest that the investigation of in vivo nitration of tyrosine and identification of nitrated peptides might be performed by precursor ion scanning for the specific immonium ion at m/z 181.06 combined with ESI-MS/MS for identification of the specific nitration sites. PMID:11433534

Petersson, A S; Steen, H; Kalume, D E; Caidahl, K; Roepstorff, P

2001-06-01

432

Storm to Seasonal Nitrate Flushing and Relationship to Hydroclimatic Conditions  

NASA Astrophysics Data System (ADS)

Coupled hydrological and geochemical cycles have historically been used to understand the mechanisms controlling chemical export at the watershed scale. Numerous studies have focused on stream geochemistry dynamics and particularly on the effects of nitrogen deposition on catchments and ecosystems. However, few studies have evaluated the variability in nitrate behavior in watersheds with different climate and hydrologic characteristics. Furthermore, storm nitrate dynamics (flushing) and corresponding relationship to discharge patterns, precipitation intensity, atmospheric deposition, and watershed properties is an area with few published studies. In the current study, we utilize hydrologic, geochemical and atmospheric data to better understand the primary processes controlling nitrate dynamics at monthly and seasonal time scales in ten watersheds located in the U.S. Stream data (discharge and nitrate concentrations) was obtained from the United States Geological Survey (USGS). Atmospheric deposition data was gathered from regional National Atmospheric Deposition Program (NADP) sites. Collected data were assessed to evaluate nitrate dynamics for the period 2000-2006. Intra-storm nitrate variability was also evaluated in a watershed in Southern California (Arroyo Seco) where estimates of dry deposition are considered some of the highest in North America. Results from our analyses show that nitrate concentration appears to respond differently in the studied watersheds, exhibiting dilution effects in some watersheds and concentration effects in others. Discharge and nitrate concentrations during the 2009 winter reveal that the Arroyo Seco watershed is characterized by distinctive flushing of nitrates within storms. The role of specific hydrological events (size, intensity and duration) on the nitrate mobilization proved to be important as well as the accumulated nitrate pool available for mobilization. In general, results show a strong linkage between hydrological and biogeochemical controls of nitrate exports. Results from this study support previous studies regarding nitrate flushing during wet seasons and also add new insight on enhanced export in areas with increased deposition rates of nitrates.

Barco, J.; Wessel, C.; Gunawan, S.; Hogue, T. S.

2009-05-01

433

Thermal decomposition of nitrated tributyl phosphate  

Microsoft Academic Search

Extended contact between heated mixtures of tri-n-butyl phosphate (TBP) and aqueous solutions of nitric acid and\\/or heavy metal nitrate salts at elevated temperatures can lead to exothermic reactions of explosive violence. Most solvent extraction operations are conducted at ambient conditions without heating TBP and have been performed safely for decades, but several explosions involving TBP have occurred in the US,

Y. Hou; E. K. Barefield; D. W. Tedder; S. I. Abdel-Khalik

1996-01-01

434

Nitrate removal by Fe-dependent denitrification  

Microsoft Academic Search

The traditional biological nitrogen removal utilizes heterotrophic denitrifying bacteria to reduce nitrate to nitrogen, through the nitrification and denitrification stages, which needs organic carbon source as the electron donor. However, several strains of Fe(II)-dependent denitrifying bacteria have been isolated in recent years, which introduced a brand-new concept and mentality for the biological nitrogen removal. It is a recent discovery of

Wang Hongyu; Yang Kai; Sun Yuchong; Ming Jianpu; Lv Bin; Yang Xiaojun

2011-01-01

435

Analysis of nitrated polynuclear aromatic hydrocarbons  

Microsoft Academic Search

A derivatization-gas chromatography\\/electron capture detector (GC\\/ECD) method has been developed for the measurement of trace nitrated polynuclear aromatic hydrocarbons (NPAHs) in air. The method involves first the derivatization of parent nitro-PAHs to their corresponding fluorinated derivatives, followed by GC\\/ECD analysis. The sensitivity of the method is an order of magnitude higher than those of direct GC\\/ECD analysis of NPAHs themselves.

Xu Jinhui; Frank S. C Lee

2001-01-01

436

(Di-methyl-phosphor-yl)methanaminium nitrate  

PubMed Central

In the crystal of the title salt, C3H11NOP+·NO3 ?, dicationic inversion dimers are head-to-tail connected by a pair of strong N—H?O hydrogen bonds. The resulting graph-set descriptor of this ring system is R 2 2(10). The nitrate counter-anions connect the dicationic dimers via N—H?O hydrogen bonds, forming two-dimensional networks in the bc plane.

Bianga, Claudia M.; Eggeling, Julia; Reiss, Guido J.

2013-01-01

437

Analytical Characterization of the Thorium Nitrate Stockpile  

Microsoft Academic Search

For several years, Oak Ridge National Laboratory (ORNL) has been supporting the Defense Logistics Agency-Defense National Stockpile Center with stewardship of a thorium nitrate (ThN) stockpile. The effort for fiscal year 2002 was to prepare a sampling and analysis plan and to use the activities developed in the plan to characterize the ThN stockpile. The sampling was performed in June

Mattus

2003-01-01

438

Equation of State of Ammonium Nitrate  

NASA Astrophysics Data System (ADS)

Ammonium nitrate (AN) is a widely used fertilizer and mining explosive. AN is commonly used in ammonium nitrate-fuel oil (ANFO), which is a mixture of explosive-grade AN prills and fuel oil in a 94:6 ratio by weight. ANFO is a non-ideal explosive with measured detonation velocities around 4 km/s. The equation of state properties and known initiation behavior of neat AN are limited. We present the results of a series of gas gun-driven plate impact experiments on pressed neat ammonium nitrate at 1.72 g/cm3. No evidence of initiation was observed under shock loading to 22 GPa. High pressure x-ray diffraction experiments in diamond anvil cells provided insight into the high pressure phase behavior over the same pressure range (to 25 GPa), as well as a static isotherm at ambient temperature. From the isotherm and thermodynamic properties at ambient conditions, a preliminary unreacted equation of state (EOS) has been developed based on the Murnaghan isotherm and Helmholtz formalism [1], which compares favorably with the available experimental Hugoniot data on several densities of AN.

Robbins, David L.; Sheffield, Stephen A.; Dattelbaum, Dana M.; Velisavljevic, Nenad; Stahl, David B.

2009-12-01

439

Isomers of nitric acid and chlorine nitrate  

SciTech Connect

Ab initio molecular orbital calculations at the HF/6-31G* and MP2/6-31G* levels have been performed on nitric acid and chlorine nitrate. Equilibrium geometries and electric dipole moments obtained from the MP2/6-31G* calculations are in good agreement with the respective experimental values, normal-mode (harmonic) vibrational frequencies and frequency shifts due to isotopic substitution calculated at this level support the most recent gas-phase infrared assignments for chlorine nitrate but suggest a reversal in the assignment of v/sub 5/ and v/sub 6/ for nitric acid. Calculations at the same levels of theory were also performed on peroxynitrous acid (HOONO) and chlorine peroxynitrite (ClOONO). The former is found to be 35 kcal/mol less stable than nitric acid at the MP2/6-31G* level; chlorine peroxynitrite is 30 kcal/mol higher in energy than chlorine nitrate. The possible role of these high-energy isomers in atmospheric processes is discussed.

McGrath, M.P.; Francl, M.M.; Rowland, F.S.; Hehre, W.J.

1988-09-22

440

Purification and Characterization of NAD(P)H:Nitrate Reductase and NADH:Nitrate Reductase from Corn Roots.  

PubMed

The nitrate reductase activity of 5-day-old whole corn roots was isolated using phosphate buffer. The relatively stable nitrate reductase extract can be separated into three fractions using affinity chromatography on blue-Sepharose. The first fraction, eluted with NADPH, reduces nearly equal amounts of nitrate with either NADPH or NADH. A subsequent elution with NADH yields a nitrate reductase which is more active with NADH as electron donor. Further elution with salt gives a nitrate reductase fraction which is active with both NADH and NADPH, but is more active with NADH. All three nitrate reductase fractions have pH optima of 7.5 and Stokes radii of about 6.0 nanometers. The NADPH-eluted enzyme has a nitrate K(m) of 0.3 millimolar in the presence of NADPH, whereas the NADH-eluted enzyme has a nitrate K(m) of 0.07 millimolar in the presence of NADH. The NADPH-eluted fraction appears to be similar to the NAD(P)H:nitrate reductase isolated from corn scutellum and the NADH-eluted fraction is similar to the NADH:nitrate reductases isolated from corn leaf and scutellum. The salt-eluted fraction appears to be a mixture of NAD(P)H: and NADH:nitrate reductases. PMID:16661853

Redinbaugh, M G; Campbell, W H

1981-07-01

441

Bismuth nitrate-induced novel nitration of estradiol: An entry to new anticancer agents.  

PubMed

Direct nitration of estradiol was carried out using metal nitrates on solid surfaces under mild condition, and a combination of bismuth nitrate pentahydrate impregnated KSF clay was found to be the best reagent to synthesize 2- and 4-nitroestradiol effectively. Furthermore, various basic side chains were introduced, through O-linker at C-3, to these nitroestradiols. The ability of these derivatives to cause cytotoxicity in Estrogen Receptor (ER)-positive and ER-negative breast cancer cell lines, as well as cancer cell lines of other origins, was examined. Qualitative structure activity relationship (SAR) has also been studied. We found that a basic side chain containing either a piperidine or morpholine ring, when conjugated to 2-nitroestradiol, was particularly effective at causing cytotoxicity in each of the cancer cell lines examined. Surprisingly, this effective cytotoxicity was even seen in ER-negative breast cancer cells. PMID:24946145

Bandyopadhyay, Debasish; Rivera, Gildardo; Sanchez, Jorge L; Rivera, Jesse; Granados, Jose C; Guerrero, Adrian M; Chang, Fang-Mei; Dearth, Robert K; Short, John D; Banik, Bimal K

2014-07-23

442

Reductive denitrification of nitrate by scrap iron filings*  

PubMed Central

Reduction of nitrate by zero-valent iron is a highly exergonic reaction that has long been known to occur. Use of scrap iron filings (SIF) as the PRB (Permeable Reactive Barrier) material can be used to recycle certain by-products, and identify cheaper replacements for expensive conventional PRB materials, especially pure metallic iron. The feasibility of reductive denitrification of nitrate by SIF was studied by batch experiments. Operational parameters such as pH value, SIF dosage and initial concentration of nitrate were investigated. The removal efficiency of nitrate reached 80% under the conditions of pH of 2.5, nitrate initial concentration of 45 mg/L and SIF dosage of 100 g/L within 4 h. Results indicated that nitrate removal is inversely related to pH. Low pH value condition favors for the nitrate transformation. Different from the results of others who studied nitrate reduction using iron powder, we found that there was a lag time before nitrate reduction occurs, even at low pH. Finally, the possible mechanism of nitrate reduction by Fe0 is discussed.

Hao, Zhi-wei; Xu, Xin-hua; Wang, Da-hui

2005-01-01

443

THE SPECTROCHEMICAL DETERMINATION OF RESIDUAL HAFNIUM IN ZIRCONIUM AN ZIRCONIUM ALLOYS USING D.C. ARC EXCITATION AND A BARIUM FLUORIDE FLUX  

Microsoft Academic Search

This method is used to determine residual hafnium in zirconium and ; Zircaloy from 30 parts per million up to 300 parts per million. By selection of ; suitable line pairs the method may be extended to include other concentration ; ranges. The oxidized sample is mixed with a one-to-one barium fluoride -graphite ; mixture and pressed into a 1\\/4

G. J. Harter; R. F. Farrell

1958-01-01

444

Atlantic Ocean Measurements of Low Molecular Weight Alkyl Nitrates  

NASA Astrophysics Data System (ADS)

The surface oceans appear to be a source of low molecular weight alkyl nitrates to the atmosphere. These compounds are converted by photolysis to NOx, and may contribute to ozone production in remote regions. The mechanism(s) of production of oceanic alkyl nitrates in surface seawater are currently unknown. Laboratory studies suggest that the reaction of peroxy radicals with nitric oxide in seawater may provide a near-surface source of these compounds. These precursors originate from the photolysis of dissolved organic matter and nitrite. Depth profiles of alkyl nitrates in the North Atlantic Ocean (Chuck et al. 2002) show elevated concentrations of alkyl nitrates below the photic zone, suggesting that non-photochemical mechanisms are also likely. We have recently completed a series of alkyl nitrate (C1-C3) depth profiles and shipboard incubation experiments in the north Atlantic, on a cruise track from Reykjavik, Iceland to Natal, Brazil (A16N2003; R/V Brown). The northernmost stations (45-50N), exhibited alkyl nitrate maxima in the mixed layer, and a positive correlation between alkyl nitrates and nitrite. In the tropics and subtropics, alkyl nitrate maxima were below the mixed layer, and alkyl nitrates correlated with nitrate. Shipboard deck irradiation studies demonstrated photochemical production of alkyl nitrates in waters that correlated with the initial nitrite concentration. Addition of nitrite stimulated production to extremely high levels, suggesting that NO, rather than peroxy radicals, is the limiting reactant in these waters. Overall, the distribution of alkyl nitrates suggests that both photochemical and microbial sources of alkyl nitrate may occur.

Dahl, E. E.; Saltzman, E. S.

2003-12-01

445

Highly enantioselective zirconium-catalyzed cyclization of aminoalkenes.  

PubMed

Aminoalkenes are catalytically cyclized in the presence of cyclopentadienylbis(oxazolinyl)borato group 4 complexes {PhB(C5H4)(Ox(R))2}M(NMe2)2 (M = Ti, Zr, Hf; Ox(R) = 4,4-dimethyl-2-oxazoline, 4S-isopropyl-5,5-dimethyl-2-oxazoline, 4S-tert-butyl-2-oxazoline) at room temperature and below, affording five-, six-, and seven-membered N-heterocyclic amines with enantiomeric excesses of >90% in many cases and up to 99%. Mechanistic investigations of this highly selective system employed synthetic tests, kinetics, and stereochemistry. Secondary aminopentene cyclizations require a primary amine (1-2 equiv vs catalyst). Aminoalkenes are unchanged in the presence of a zirconium monoamido complex {PhB(C5H4)(Ox(4S-iPr,Me2))2}Zr(NMe2)Cl or a cyclopentadienylmono(oxazolinyl)borato zirconium diamide {Ph2B(C5H4)(Ox(4S-iPr,Me2))}Zr(NMe2)2. Plots of initial rate versus [substrate] show a rate dependence that evolves from first-order at low concentration to zero-order at high concentration, and this is consistent with a reversible substrate-catalyst interaction preceding an irreversible step. Primary kinetic isotope effects from substrate conversion measurements (k'obs((H))/k'obs((D)) = 3.3 ± 0.3) and from initial rate analysis (k2((H))/k2((D)) = 2.3 ± 0.4) indicate that a N-H bond is broken in the turnover-limiting and irreversible step of the catalytic cycle. Asymmetric hydroamination/cyclization of N-deutero-aminoalkenes provides products with higher optical purities than obtained with N-proteo-aminoalkenes. Transition state theory, applied to the rate constant k2 that characterizes the irreversible step, provides activation parameters consistent with a highly organized transition state (?S(++) = -43(7) cal·mol(-1) K(-1)) and a remarkably low enthalpic barrier (?H(++) = 6.7(2) kcal·mol(-1)). A six-centered, concerted transition state for C-N and C-H bond formation and N-H bond cleavage involving two amidoalkene ligands is proposed as most consistent with the current data. PMID:23631736

Manna, Kuntal; Everett, William C; Schoendorff, George; Ellern, Arkady; Windus, Theresa L; Sadow, Aaron D

2013-05-15

446

Cesium Adsorption on the ZIRCONIUM/OXYGEN/TUNGSTEN(100) Surface.  

NASA Astrophysics Data System (ADS)

Interest in zirconium covered tungsten as an electrode material has been stimulated by recent work on the model surface Zr/O/W(100). This surface has been shown to have an effective thermionic work function of (TURN) 2.6 eV, when properly prepared, with very low volatility and excellent thermal stability. For advanced thermionic converter applications and for proposed future nuclear electric propulsion systems, the emitter requirement is (phi)(,eff) (LESSTHEQ) 2.4 eV at 1600 K. The corresponding collector must have a work function <(, )1.4 eV at (TURN) 600 K. For any electrode materials yet studied, these requirements dictate the presence of an equilibrium pressure of cesium vapor. The adsorption/desorption characteristics of cesium in the Zr/O/W(100) surface and the effect of cesium coverage on the surface work function have been studied, using Auger electron spectrometry (AES), field emission retarding potential work function measurements (FERP) and thermal desorption mass spectrometry (TDS). The minimum work function attained for cesium adsorption on the Zr/O/W(100) surface was 2.12 eV. The desorption spectrum of cesium from this surface shows major binding states at 1.1 and 1.3 eV, with desorption complete at T (LESSTHEQ) 900 K. Adsorption of excess oxygen on the low work function Zr/O/W(100) surface increases the affinity of the surface toward cesium and lowers the minimum work function. Cesium adsorbed on a saturated layer of excess oxygen shows a terminal desorption temperature of 1300 K and minimum work function of 1.37 eV. Thermal equilibrium of the excess oxygen removes some oxygen and zirconium from the surface, changing the cesium adsorption characteristics. Measurement of low energy electron reflection from the Zr/O/W(100) surface with and without adsorbed cesium indicates that the presence of cesium reduces the reflection coefficient of Zr/O/W(100) near the threshold beam potential for current collection. Two adsorption sites for Cs adsorption on clear W(100) were found in the thermal desorption spectra. The Cs/W(100) bonding is stronger than the bonding of Cs on Zr/O/W(100) surface.

Chen, Hsiung-Ku.

447

Synthesis and liquid crystal phase transitions of zirconium phosphate disks  

NASA Astrophysics Data System (ADS)

Solvent-mediated self-assembly of nanoparticles is an effective and efficient way for the bottom-up organization of functional structures. The primary object of this work is to build up a model system for the study of suspensions of disk-shaped nanoparticles, and use it for the study of self-assembly and discotic liquid crystal phase transitions of discotic particles. The work was introduced by the control over the size and polydispersity of zirconium phosphate (ZrP) disks through synthesis. Systematic experiments revealed that regular-shaped alpha-zirconium phosphate crystalline disks with a size-to-thickness ratio from 1 to 50 and size polydispersity as low as 0.2 can be obtained through hydrothermal treatment in 3 M to 15 M phosphoric acid solutions. Transmission and scanning electron micrographs revealed that the growth of the disks is mediated by oriented attachment, which happened continuously throughout the hydrothermal treatment between various sized disks. Ostwald ripening is effective in improving the regularity of the shape of the disks, especially under prolonged hydrothermal treatment. Under the microwave assisted hydrothermal conditions, the rate of attachment on the flat surfaces of the disks is accelerated, which leads to the formation of the column-shaped crystals. With the ability to adjust the size, aspect ratio, and polydispersity of ZrP disks, the study on self-assembly behavior and the discotic liquid crystal phases was enabled. Firstly, liquid crystal phases of aqueous suspensions of ZrP disks were investigated. Iridescent smectic phase and the critical points of phase transitions were found. Moreover, monolayer ZrP nanosheets with extremely high aspect ratio, which were achieved by exfoliating the ZrP crystals, were also used in this study. The high aspect ratio of nanosheets produces a laminar phase at low nanosheet concentration. Chiral liquid crystal phases were demonstrated when increased the concentration of the nanosheets. The competition between the chirality and layering leads to twisted and layered structures. For the final part, solvent-mediated self-assembly of disks and nanosheets via undulation of liquid crystal phases showed an interesting approach for bottom-up design of functional nano-structures.

Shuai, Min

448

Effect of Sodium Nitrate and Nitrate Reducing Bacteria on In vitro Methane Production and Fermentation with Buffalo Rumen Liquor  

PubMed Central

Nitrate can serve as a terminal electron acceptor in place of carbon dioxide and inhibit methane emission in the rumen and nitrate reducing bacteria might help enhance the reduction of nitrate/nitrite, which depends on the type of feed offered to animals. In this study the effects of three levels of sodium nitrate (0, 5, 10 mM) on fermentation of three diets varying in their wheat straw to concentrate ratio (700:300, low concentrate, LC; 500:500, medium concentrate, MC and 300:700, high concentrate, HC diet) were investigated in vitro using buffalo rumen liquor as inoculum. Nitrate reducing bacteria, isolated from the rumen of buffalo were tested as a probiotic to study if it could help in enhancing methane inhibition in vitro. Inclusion of sodium nitrate at 5 or 10 mM reduced (p<0.01) methane production (9.56, 7.93 vs. 21.76 ml/g DM; 12.20, 10.42 vs. 25.76 ml/g DM; 15.49, 12.33 vs. 26.86 ml/g DM) in LC, MC and HC diets, respectively. Inclusion of nitrate at both 5 and 10 mM also reduced (p<0.01) gas production in all the diets, but in vitro true digestibility (IVTD) of feed reduced (p<0.05) only in LC and MC diets. In the medium at 10 mM sodium nitrate level, there was 0.76 to 1.18 mM of residual nitrate and nitrite (p<0.01) also accumulated. In an attempt to eliminate residual nitrate and nitrite in the medium, the nitrate reducing bacteria were isolated from buffalo adapted to nitrate feeding and introduced individually (3 ml containing 1.2 to 2.3×106 cfu/ml) into in vitro incubations containing the MC diet with 10 mM sodium nitrate. Addition of live culture of NRBB 57 resulted in complete removal of nitrate and nitrite from the medium with a further reduction in methane and no effect on IVTD compared to the control treatments containing nitrate with autoclaved cultures or nitrate without any culture. The data revealed that nitrate reducing bacteria can be used as probiotic to prevent the accumulation of nitrite when sodium nitrate is used to reduce in vitro methane emissions.

Sakthivel, Pillanatham Civalingam; Kamra, Devki Nandan; Agarwal, Neeta; Chaudhary, Lal Chandra

2012-01-01

449

Nitrate sources and sinks in Elkhorn Slough, California: Results from long-term continuous in situ nitrate analyzers  

USGS Publications Warehouse

Nitrate and water quality parameters (temperature, salinity, dissolved oxygen, turbidity, and depth) were measured continuously with in situ NO 3 analyzers and water quality sondes at two sites in Elkhorn Slough in Central California. The Main Channel site near the mouth of Elkhorn Slough was sampled from February to September 2001. Azevedo Pond, a shallow tidal pond bordering agricultural fields further inland, was sampled from December 1999 to July 2001. Nitrate concentrations were recorded hourly while salinity, temperature, depth, oxygen, and turbidity were recorded every 30 min. Nitrate concentrations at the Main Channel site ranged from 5 to 65 ??M. The propagation of an internal wave carrying water from ???100 m depth up the Monterey Submarine Canyon and into the lower section of Elkhorn Slough on every rising tide was a major source of nitrate, accounting for 80-90% of the nitrogen load during the dry summer period. Nitrate concentrations in Azevedo Pond ranged from 0-20 ??M during the dry summer months. Nitrate in Azevedo Pond increased to over 450 ??M during a heavy winter precipitation event, and interannual variability driven by differences in precipitation was observed. At both sites, tidal cycling was the dominant forcing, often changing nitrate concentrations by 5-fold or more within a few hours. Water volume flux estimates were combined with observed nitrate concentrations to obtain nitrate fluxes. Nitrate flux calculations indicated a loss of 4 mmol NO3 m -2 d-1 for the entire Elkhorn Slough and 1 mmol NO 3 m-2 d-1 at Azevedo Pond. These results suggested that the waters of Elkhorn Slough were not a major source of nitrate to Monterey Bay but actually a nitrate sink during the dry season. The limited winter data at the Main Channel site suggest that nitrate was exported from Elkhorn Slough during the wet season. Export of ammonium or dissolved organic nitrogen, which we did not monitor, may balance some or all of the NO 3 flux.

Chapin, T. P.; Caffrey, J. M.; Jannasch, H. W.; Coletti, L. J.; Haskins, J. C.; Johnson, K. S.

2004-01-01

450

Evaluating Ecosystem Services for Reducing Groundwater Nitrate Contamination: Nitrate Attenuation in the Unsaturated and Saturated Zones  

NASA Astrophysics Data System (ADS)

Nitrates are the most common type of groundwater contamination in agricultural regions. Environmental policies targeting nitrates have focused on input control (e.g., restricted fertilizer application), intermediate loads control (e.g., reduce nitrate leached from crop fields), and final loads control (e.g., reduce catchment nitrate loads). Nitrate loads can be affected by hydrological processes in both unsaturated and saturated zones. Although many of these processes have been extensively investigated in literature, they are commonly modeled as exogenous to farm management. A couple of recent studies by scientists from the Lawrence Livermore National Laboratory show that in some situations nitrate attenuation processes in the unsaturated/saturated zone, particularly denitrification, can be intensified by certain management practices to mitigate nitrate loads. Therefore, these nitrate attenuation processes can be regarded as a set of ecosystem services that farmers can take advantage of to reduce their cost of complying with environmental policies. In this paper, a representative California dairy farm is used as a case study to show how such ecosystem attenuation services can be framed within the farm owner's decision-making framework as an option for reducing groundwater nitrate contamination. I develop an integrated dynamic model, where the farmer maximizes discounted net farm profit over multiple periods subject to environmental regulations. The model consists of three submodels: animal-waste-crop, hydrologic, and economic model. In addition to common choice variables such as irrigation, fertilization, and waste disposal options, the farmer can also endogenously choose from three water sources: surface water, deep groundwater (old groundwater in the deep aquifer that is not affected by farm effluent in the short term), and shallow groundwater (drainage water that can be recycled via capture wells at the downstream end of the farm). The capture wells not only recycle wastewater, but can also increase the likelihood of denitrification. Thus the farmer essentially can choose whether, and to which extent, to install capture wells and take advantage of the ecosystem attenuation services. Decision rules from the dynamic optimization model demonstrate best management practices for the farm to improve its economic and environmental performance. I further use an economic valuation technique to value these services. Under the Millennium Ecosystem Assessment framework, nitrate attenuation in the unsaturated and saturated zone provides regulatory ecosystem services to humans, mainly nutrient regulation and waste treatment. With the integrated farm model, the production function approach is adopted to get the economic value of these regulatory services. The results highlight the significant role the environment can play in nitrate pollution control and potential benefits from designing policies that acknowledge this role. The most desirable policies are those that create incentive for farmers to use potential ecosystem services, which significantly reduce environmental compliance costs and increase social welfare.

Wang, J.

2013-12-01

451

A comparative study of zirconium and titanium implants in rat: osseointegration and bone material quality.  

PubMed

Permanent metal implants are widely used in human medical treatments and orthopedics, for example as hip joint replacements. They are commonly made of titanium alloys and beyond the optimization of this established material, it is also essential to explore alternative implant materials in view of improved osseointegration. The aim of our study was to characterize the implant performance of zirconium in comparison to titanium implants. Zirconium implants have been characterized in a previous study concerning material properties and surface characteristics in vitro, such as oxide layer thickness and surface roughness. In the present study, we compare bone material quality around zirconium and titanium implants in terms of osseointegration and therefore characterized bone material properties in a rat model using a multi-method approach. We used light and electron microscopy, micro Raman spectroscopy, micro X-ray fluorescence and X-ray scattering techniques to investigate the osseointegration in terms of compositional and structural properties of the newly formed bone. Regarding the mineralization level, the mineral composition, and the alignment and order of the mineral particles, our results show that the maturity of the newly formed bone after 8 weeks of implantation is already very high. In conclusion, the bone material quality obtained for zirconium implants is at least as good as for titanium. It seems that the zirconium implants can be a good candidate for using as permanent metal prosthesis for orthopedic treatments. PMID:24170339

Hoerth, Rebecca M; Katunar, María R; Gomez Sanchez, Andrea; Orellano, Juan C; Ceré, Silvia M; Wagermaier, Wolfgang; Ballarre, Josefina

2014-02-01

452

Increased force simulator wear testing of a zirconium oxide total knee arthroplasty.  

PubMed

Total knee replacements provide cost effective treatment for debilitating conditions such as osteoarthritis. Their long term performance is governed by ultra-high molecular weight polyethylene (UHMWPE) wear which produces wear debris leading to osteolysis and aseptic loosening of the implant. An oxidised zirconium alternative to cobalt chrome is being used to reduce wear debris formation in the younger patients. Two TKRs of cobalt chrome and two of zirconium oxide coated zirconium were tested in a six degrees of freedom of motion, Stanmore-Instron force controlled knee wear simulator over 4 million increased force cycles. Oxidised zirconium was demonstrated to be more scratch resistant than CoCr. Increases in Ra (mean average roughness) of 12-fold compared to 1.9 fold rise for ZrO. The differences in roughness were accompanied by a 78%, statistically significant, reduction in wear of UHMWPE with the ZrO femoral components compared to the CoCr (p=0.037). Long term clinical results from the use of oxidised zirconium femoral components are awaited. However, it shows potential to reduce the wear rate. PMID:19321347

Lee, Joshua K L; Maruthainar, Kunalan; Wardle, Nic; Haddad, Fares; Blunn, Gordon W

2009-08-01

453

Separation of hafnium from zirconium in sulfuric acid solutions using pressurized ion exchange  

SciTech Connect

High-resolution pressurized ion exchange has been used successfully to study and separate hafnium and zirconium sulfate complexes by chromatographic elution from Dowex 50W-X8 (15 to 25 ..mu..m) resin with sulfuric acid solutions. Techniques were developed to continuously monitor the column effluents for zirconium and hafnium by reaction with fluorometric and colorimetric reagents. Since neither reagent was specific for either metal ion, peak patterns were initially identified by using the stable isotopes /sup 90/Zr and /sup 180/Hf as fingerprints of their elution position. Distribution ratios for both zirconium and hafnium decrease as the inverse fourth power of the sulfuric acid concentration below 2N and as the inverse second power at higher acid concentration. The hafnium-to-zirconium separation factor is approximately constant (approx. 8) over the 0.5 to 3N range. Under certain conditions, an unseparated fraction was observed that was not retained by the resin. The amount of this fraction which is thought to be a polymeric hydrolysis product appears to be a function of metal and sulfuric acid concentrations. Conditions are being sought to give the highest zirconium concentration and the lowest acid concentration that can be used as a feed material for commercial scale-up in the continuous annular chromatographic (CAC) unit without formation of the polymer.

Hurst, F.J.

1981-01-01

454

Emulsions stabilized by precipitates of zirconium and tributyl phosphate degradation products  

SciTech Connect

In the Purex process, a solvent extraction method of nuclear fuel reprocessing, a stable emulsion called crud forms at the interface between the oil and water phases. This paper reports that crud is an emulsion stabilized by finely dispersed solids. Insoluble residues and precipitates of zirconium and radiation-degraded products of tributyl phosphate (TBP) are key materials in crud formation. Cruds formed by precipitates of zirconium and TBP degradation products, such as di-n-butyl phosphate (HDBP), mono-n-butyl phosphate (H{sub 2}MBP), and phosphoric acid (H{sub 3}PO{sub 4}) are studied. Experimental results show that the precipitate of zirconium and HDBP is not effective in stabilizing emulsions. However, the refractory complex of zirconium and H{sub 3}PO{sub 4} is an important material for stabilizing an oil-in-water emulsion in a solution with or without uranium. Moreover, it is shown that the complex of zirconium and H{sub 2}MBP has a significant role in stabilizing a water-in-oil emulsion, especially when uranium is also present.

Sugai, H.; Munakata, K. (Sumitomo Metal Mining Co., Ltd., Tokai Research Center 2600, Ishigamitojuku, Tokai-mura, Ibaraki-ken 319-11 (JP)); Miyachi, S.; Yasu, S. (Power Reactor and Nuclear Fuel Development Corp., Tokai Works Reprocessing Plant, Analysis Section, Tokai-mura, Ibaraki-ken 319-11 (JP))

1992-05-01

455

Determination of trace iron in zirconium by isotope dilution-thermal ionization mass spectrometry  

NASA Astrophysics Data System (ADS)

An isotope dilution-thermal ionization mass spectrometry method for the determination of parts-per-million levels of iron in zirconium is required for precise, accurate analyses in studies of the effects of iron on the irradiation deformation of nuclear alloys. A two-stage purification procedure was developed to avoid the signal suppression and interference caused by the zirconium matrix. After sample dissolution and spiking with 54Fe, the bulk of the zirconium is removed by ion exchange chromatography, and the eluted Fe(III) is further purified by micro-solvent extraction into tributyl phosphate-impregnated resin beads. The iron is back-extracted, submicrogram amounts are loaded onto previously outgassed zone-refined Re filaments, and 54/56 ratios are measured at 1170°C. A silica gel/boric acid ionization enhancer is used to obtain stable Fe+ currents as strong as 2 × 10-14. A from nanogram loadings of pure iron. The procedural blank of 20 ± 6 ng is sufficiently low to allow determination of ppm levels of iron in 0.1 g zirconium samples. The analyses of solution standards showed agreement within 2% between measured and expected values, and a good fit, r2 = 0.99997, to a linear regression. The analyses of metal standards exhibited a similar good fit to a linear regression of measured against expected values, and showed good agreement with other methods. The method meets the requirements for zirconium metallurgical studies, and may be extended to other applications.

Elliot, N. L.; Campbell, M. A.; Green, L. W.

1995-08-01

456

Synthesis of zirconium tungstate-zirconia core-shell composite particles  

SciTech Connect

Highlights: {yields} ZrW{sub 2}O{sub 8}-ZrO{sub 2} core-shell particles to offer solutions for sintering problems. {yields} Core synthesis by a precursor based on tungstic acid and zirconium acetate. {yields} Shell phase by urea hydrolysis in the presence of zirconium ions. {yields} [Urea]/[ZrOCl{sub 2}] ratio controls the rate of shell precursor precipitation. -- Abstract: In this work, ZrW{sub 2}O{sub 8}-ZrO{sub 2} core-shell composite particles were synthesized. ZrW{sub 2}O{sub 8} that was used in the core is a material with negative coefficient of thermal expansion, and it was synthesized from a high-pH precursor based on use of tungstic acid and zirconium acetate. Shell layer was composed of ZrO{sub 2} nanocrystallites and precipitated from an aqueous solution by urea hydrolysis. While volume of the shell was effectively controlled by the initial zirconium ion concentration in the solutions, the rate of precipitation was a function of the ratio of initial concentrations of urea to zirconium ions. It is hypothesized that isolation of the ZrW{sub 2}O{sub 8} within a layer of ZrO{sub 2}, will be a key element in solving problems associated with reactivity of ZrW{sub 2}O{sub 8} towards other components in sintering of ceramic-ceramic composites with tuned or zero thermal expansion coefficient.

Khazeni, Nasser, E-mail: khazeni.n@gmail.com [Chemical Engineering Department, Middle East Technical University, Ankara 06531 (Turkey)] [Chemical Engineering Department, Middle East Technical University, Ankara 06531 (Turkey); Mavis, Bora, E-mail: bmavis@hacettepe.edu.tr [Mechanical Engineering Department, Hacettepe University, Beytepe Ankara 06800 (Turkey)] [Mechanical Engineering Department, Hacettepe University, Beytepe Ankara 06800 (Turkey); Guenduez, Guengoer, E-mail: ggunduz@metu.edu.tr [Chemical Engineering Department, Middle East Technical University, Ankara 06531 (Turkey)] [Chemical Engineering Department, Middle East Technical University, Ankara 06531 (Turkey); Colak, Uner, E-mail: ucolak@hacettepe.edu.tr [Nuclear Engineering Department, Hacettepe University, Beytepe Ankara 06800 (Turkey)] [Nuclear Engineering Department, Hacettepe University, Beytepe Ankara 06800 (Turkey)

2011-11-15

457

Glucose elevates NITRATE TRANSPORTER2.1 protein levels and nitrate transport activity independently of its HEXOKINASE1-mediated stimulation of NITRATE TRANSPORTER2.1 expression.  

PubMed

Mineral nutrient uptake and assimilation is closely coordinated with the production of photosynthate to supply nutrients for growth. In Arabidopsis (Arabidopsis thaliana), nitrate uptake from the soil is mediated by genes encoding high- and low-affinity transporters that are transcriptionally regulated by both nitrate and photosynthate availability. In this study, we have studied the interactions of nitrate and glucose (Glc) on gene expression, nitrate transport, and growth using glucose-insensitive2-1 (gin2-1), which is defective in sugar responses. We confirm and extend previous work by showing that HEXOKINASE1-mediated oxidative pentose phosphate pathway (OPPP) metabolism is required for Glc-mediated NITRATE TRANSPORTER2.1 (NRT2.1) expression. Treatment with pyruvate and shikimate, two products derived from intermediates of the OPPP that are destined for amino acid production, restores wild-type levels of NRT2.1 expression, suggesting that metabolites derived from OPPP metabolism can, together with Glc, directly stimulate high levels of NRT2.1 expression. Nitrate-mediated NRT2.1 expression is not influenced by gin2-1, showing that Glc does not influence NRT2.1 expression through nitrate-mediated mechanisms. We also show that Glc stimulates NRT2.1 protein levels and transport activity independently of its HEXOKINASE1-mediated stimulation of NRT2.1 expression, demonstrating another possible posttranscriptional mechanism influencing nitrate uptake. In gin2-1 plants, nitrate-responsive biomass growth was strongly reduced, showing that the supply of OPPP metabolites is essential for assimilating nitrate for growth. PMID:24272701

de Jong, Femke; Thodey, Kate; Lejay, Laurence V; Bevan, Michael W

2014-01-01

458

Sulfate and nitrate collected by filter sampling near the tropopause  

NASA Technical Reports Server (NTRS)

Filter samples collected near the tropopause with an F-106 aircraft and two Boeing 747 aircraft were analyzed for sulfate and nitrate ion content. Within the range of routine commercial flight altitudes (at or below 12.5 km), stratospheric mass mixing ratios for the winter-spring group averaged 0.26 ppbm for sulfate and 0.35 ppbm for nitrate. For the summer-fall group, stratosphere mixing ratios averaged 0.13 ppbm and 0.25 ppbm for sulfate and nitrate, respectively. Winter-spring group tropospheric mass mixing ratios averaged 0.08 ppbm for sulfate and 0.10 ppbm for nitrate, while summer-fall group tropospheric mixing ratios averaged 0.05 ppbm for sulfate and 0.08 ppbm for nitrate. Correlations of the filter data with available ozone data suggest that the sulfate and nitrate are transported from the stratosphere to the troposphere.

Humenik, F. M.; Lezberg, E. A.; Otterson, D. A.

1980-01-01

459

Characterization of Nitrate Reductase Deficient Mutants of Chlorella sorokiniana  

PubMed Central

After x-ray irradiation, 13 mutants of Chlorella sorokiniana incapable of using NO3? as N source were isolated using a pinpoint method. Using immunoprecipitation and Western blot assays, no nitrate reductase was found in five strains while in eight mutants the enzyme was detected. The latter strains contained different patterns of nitrate reductase partial reactions. All isolates were of the nia-type as indicated by the inducibility of purine hydroxylase I and by complementation of nitrate reductase activity in the Neurospora crassa mutant Nit-1. A restoration of NADP-nitrate reductase in Nit-1 was also obtained with NH4+-grown cells indicating that Mo-cofactor is constitutive in Chlorella. Complementation experiments among the Chlorella mutants resulted in restoration of NADH-nitrate reductase activity. The characteristics of some of the Chlorella mutants are discussed in view of an improper orientation of Mo-cofactor in the residual nitrate reductase protein. Images Figure 3

Knobloch, Otto; Tischner, Rudolf

1989-01-01

460

SURFACE MODIFICATION OF ZIRCALOY-4 SUBSTRATES WITH NICKEL ZIRCONIUM INTERMETALLICS  

SciTech Connect

Surfaces of Zircaloy-4 (Zr-4) substrates were modified with nickel-zirconium (NiZr) intermetallics to tailor oxidation performance for specialized applications. Surface modification was achieved by electroplating Zr-4 substrates with nickel (Ni) and then performing thermal treatments to fully react the Ni plating with the substrates, which resulted in a coating of NiZr intermetallics on the substrate surfaces. Both plating thickness and thermal treatment were evaluated to determine the effects of these fabrication parameters on oxidation performance and to identify an optimal surface modification process. Isothermal oxidation tests were performed on surface-modified materials at 290°, 330°, and 370°C under a constant partial pressure of oxidant (i.e., 1 kPa D2O in dry Ar at 101 kPa) for 64 days. Test results revealed an enhanced, transient oxidation rate that decreased asymptotically toward the rate of the Zr-4 substrate. Oxidation kinetics were analyzed from isothermal weight gain data, which were correlated with microstructure, hydrogen pickup, strength, and hardness.

Luscher, Walter G.; Gilbert, Edgar R.; Pitman, Stan G.; Love, Edward F.

2013-02-01

461

Surface modification of Zircaloy-4 substrates with nickel zirconium intermetallics  

NASA Astrophysics Data System (ADS)

Surfaces of Zircaloy-4 (Zr-4) substrates were modified with nickel-zirconium (NiZr) intermetallics to tailor oxidation performance for specialized applications. Surface modification was achieved by electroplating Zr-4 substrates with nickel (Ni) and then performing thermal treatments to fully react the Ni plating with the substrates, which resulted in a coating of NiZr intermetallics on the substrate surfaces. Both plating thickness and thermal treatment were evaluated to determine the effects of these fabrication parameters on oxidation performance and to identify an optimal surface modification process. Isothermal oxidation tests were performed on surface-modified materials at 290°, 330°, and 370 °C under a constant partial pressure of oxidant (i.e., 1 kPa D2O in dry Ar at 101 kPa) for 64 days. Test results revealed an enhanced, transient oxidation rate that decreased asymptotically toward the rate of the Zr-4 substrate. Oxidation kinetics were analyzed from isothermal weight gain data, which were correlated with microstructure, hydrogen pickup, strength, and hardness.

Luscher, Walter G.; Gilbert, Edgar R.; Pitman, Stan G.; Love, Edward F.

2013-02-01

462

Glucose sensor based on glucose oxidase immobilized by zirconium phosphate.  

PubMed

Amperometric glucose sensors were fabricated using glucose oxidase (GOx) entrapped in zirconium hydrogenphosphate (ZrP), and their performance was evaluated. Reportedly, alpha-ZrP is one of the candidates that are expected to improve the stability of enzymes immobilized on solid surfaces. We intercalated GOxs into ZrP (GOx/ZrP), cast the GOx/ZrP suspension in polyvinylalcohol on a platinum electrode, and dried it in a vacuum oven. The morphological layered structure was investigated by scanning electron microscopy. The enzymatic activities, which were determined by open-circuit potentiometric technique, reached the highest when GOxs were immobilized in ZrP at ca. pH 5. In vitro tests showed good linear responses in the 0-25 mM range and the sensitivity of 0.14 nA mM(-1) at 0.4 V vs. Ag/AgCl. The sensors, as made, were stable for more than 3 days within a limited deterioration. PMID:15636507

Park, Sejin; Chung, Taek Dong; Kang, Sun Kil; Jeong, Ran-A; Boo, Hankil; Kim, Hee Chan

2004-12-01

463

Radioactive potential of zirconium-dioxide used for dental applications.  

PubMed

Purpose: The purpose of this study was to investigate the possible radioactive potential of zirconium dioxide (ZrO2) dental ceramics. Such information is necessary since they became an integral part of routine prosthetic rehabilitations and devoid of scientific information about their radioactivity creates some concern in the dental community. Methods: Four different types of commercial ZrO2 ceramics, namely Lava, Cercon, ICE Zirkon, and Everest Bio ZS were investigated before and after the sintering process. Sintering temperatures were applied according to each manufacturer's instructions. The compositions of the presintered and sintered specimens were analyzed using x-Ray Fluorescence Spectrometer (XRF). Concentrations of the elements and compounds were also measured by this method. Determination of radioactivity continued with Gamma-spectrometry measurements and Gross alpha/Beta analyses. Results: The activity of gamma and Gross alpha/beta was below minimum detection limits (MDL) for presintered and sintered ZrO2. The MDLs of gross alpha/beta counting system were 0.02 Bq/g and 0.01 Bq/g for alpha and beta radioactivity, respectively. The sintering process played only a minor role in the composition of the compounds. Conclusions: Radioactivity of the ZrO2 ceramics studied showed negligible radionuclide activity that can be considered lower than many hazardous radioactive appliances in our environment. PMID:22865573

Bavbek, Andac Barkin; Ozcan, Mutlu; Eskitascioglu, Gürcan

2014-01-01

464

Anisotropy of point defect diffusion in alpha-zirconium  

NASA Astrophysics Data System (ADS)

Two types of intrinsic defect, i.e., vacancy and self-interstitial atom (SIA), are formed in metals during irradiation with energetic particles. The evolution of defect population leads to significant changes in microstructure and causes a number of radiation-induced property changes. Some phenomena, such as radiation growth of anisotropic materials, are due to anisotropy in the atomic mass transport by point defects. Detailed information on atomic-scale mechanisms is, therefore, necessary to understand such phenomena. In this article, we present results of a computer simulation study of mass transport via point defects in alpha-zirconium. The matrix of self-diffusion coefficients and activation energies for vacancy and SIA defects have been obtained, and different methods of treatment of diffusion have been tested. Molecular dynamics (MD) shows that vacancy diffusion is approximately isotropic in the temperature range studied (1050 to 1650 K), although some preference for basalplane diffusion was observed at the lower end of the range. The mechanism of interstitial diffusion changes from one-dimensional (1-D) in a <11bar 20> direction at low temperature (<300 K) to two-dimensional (2-D) in the basal plane and, then, three-dimensional (3-D) at higher temperatures.

Osetsky, Y. N.; Bacon, D. J.; de Diego, N.

2002-03-01

465

Gadolinium-hydrogen ion exchange of zirconium phosphate  

NASA Technical Reports Server (NTRS)

The Gd(+3)/H(+) ion exchange on a commercial zirconium phosphate ion exchanger was investigated in chloride, sulfate, and phosphate solutions of Gd(+3) at gadolinium concentrations of 0.001 to 1 millimole per cc and in the pH range of 0 to 3.5. Relatively low Gd(+3) capacities, in the range of 0.01 to 0.1 millimole per g of ion exchanger were found at room temperature. A significant difference in Gd(+3) sorption was observed, depending on whether the ion exchanger was converted from initial conditions of greater or lesser Gd(+3) sorption than the specific final conditions. Correlations were found between decrease in Gd(+3) capacity and loss of exchanger phosphate groups due to hydrolysis during washing and between increase in capacity and treatment with H3PO4. Fitting of the experimental data to ideal ion exchange equilibrium expressions indicated that each Gd(+3) ion is sorbed on only one site of the ion exchanger. The selectivity quotient was determined to be 2.5 + or - 0.4 at room temperature on gadolinium desorption in chloride solutions.

Liu, D. C.; Power, J. L.

1972-01-01

466

High temperature oxidation of some zirconium alloys in flowing oxygen  

NASA Astrophysics Data System (ADS)

The oxidation behavior of three zirconium alloys, Zr-2.2wt%Hf, Zr-2.5wt%Nb and Zr-3wt%Nb-1wt%Sn, has been studied in flowing oxygen in the temperature range 873-1173 K to 120 ks (2000 min). Zr-2.5Nb and Zr-3Nb-1Sn showed a transition to rapid linear kinetics after initial parabolic oxidation at all temperatures. Zr-2.2Hf, on the other hand, showed this transition at temperatures in the range 973-1173 K; no transition was observed at 873 K within the oxidation times reported. Zr-2.2Hf showed the smallest weight gains, followed by Zr-2.5Nb and Zr-3Nb-1Sn. Increased oxidation rates and shorter time-to-rate transition of Zr-2.5Nb and Zr-3Nb-1Sn as compared with Zr-2.2Hf are attributed to the presence of the alloying elements Nb, Sn and Hf. Based on the Nomura-Akutsu model, Hf should delay the rate transition, while Nb and Sn lead to shorter transition times. The scale on Zr-2.2Hf was identified as monoclinic zirconia, while the tetragonal phase, 6ZrO 2 · Nb 2O 5, was contained in the monoclinic zirconia scales on both other alloys.

Kohli, Rajiv

1980-06-01

467

Microstructure and mechanical properties of proton irradiated zirconium carbide  

NASA Astrophysics Data System (ADS)

Zirconium carbide is a candidate ceramic being considered for metal-carbide-base composite-type fuels, as well as for an alternative coating material for TRISO particle fuels. Ensuring adequate mechanical properties and dimensional stability in response to radiation is a key part in developing a practical ZrC-base fuel. The existing available radiation response data for ZrC is limited and insufficient. In the present study, ZrC was irradiated with a 2.6 MeV proton beam at 800 °C to doses of 0.7 and 1.5 dpa. Following radiation, the radiation induced damage microstructure is comprised of a high density of nanometer-sized Frank loops, but no irradiation induced amorphization, voids, or precipitates were observed. A slight lattice expansion was found in the irradiated ZrC, in good agreement with the reported results from neutron irradiation. The changes in microhardness and fracture toughness properties induced in the irradiated samples were measured using indentation techniques. The hardness and the fracture toughness both increase with increasing radiation dose.

Yang, Yong; Dickerson, Clayton A.; Swoboda, Hannah; Miller, Brandon; Allen, Todd R.

2008-09-01

468

Dynamic restoration mechanisms in {alpha}-zirconium at elevated temperatures  

SciTech Connect

The creep behavior of {alpha}-zirconium at high temperatures is not understood. Recently, steady-state stress exponents between 5 and 7 have been suggested over a range of elevated temperatures, indicating the predominance of dislocation climb (dynamic recovery) as the restoration mechanism. However, the activation energies are significantly higher than those of self-diffusion of pure Zr, as expected from climb-controlled mechanisms. This discrepancy and the observations of increased high-angle grain boundary area with straining have been attributed to the possible occurrence of discontinuous recrystallization and/or grain growth as additional restoration mechanisms. Tension, torsion and creep tests to small and large strains were performed at temperatures from 400 to 800 deg C. The microstructure of the deformed samples was characterized by optical microscopy, transmission electron microscopy, as well as texture analysis using X-ray and electron backscatter diffraction. Dynamic recovery through dislocation climb appears to be the prevailing restoration mechanism. The increase in high angle boundary area with larger strains is a consequence of geometric dynamic recrystallization.

Perez-Prado, M.T. [Department of Physical Metallurgy, CENIM-CSIC, Avda. de Gregorio del Amo, 8, 28040 Madrid (Spain)]. E-mail: tpprado@cenim.csic.es; Barrabes, S.R. [Department of Aerospace and Mechanical Engineering, University of Southern California, Olin Hall 430, Los Angeles, CA 90089 (United States); Kassner, M.E. [Department of Aerospace and Mechanical Engineering, University of Southern California, Olin Hall 430, Los Angeles, CA 90089 (United States); Evangelista, E. [Department of Mechanics, Polytechnic University of Marche, Ancona 60131 (Italy)

2005-02-01

469

Revisiting Zirconium: New Abundance Determinations with Improved Oscillator Strengths  

NASA Astrophysics Data System (ADS)

The element Zirconium is produced via neutron capture (n-capture). It resides in the mass range where there is uncertainty about the production mechanism at early time. The rapid n-capture process (r-process) was believed to be responsible for th