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1

Effect of oxide additives on radiolytic decomposition of zirconium and thorium nitrates  

Microsoft Academic Search

Gamma ray-induced decomposition of the binary mixtures of zirconium and thorium nitrates with 2.5, 5 and 10 mol% of V2O5, PbO, ThO2, ZrO2, and MnO2 has been studied at different doses up to 260 kGy. Radiation chemical yield G(NO2?)-values are enhanced by V2O5, PbO, and ThO2 but are decreased by ZrO2 and MnO2. The effect of radiation dose on the

N. G. Joshi; A. N. Garg; V. Natarajan; M. D. Sastry

1996-01-01

2

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

3

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

4

The influence of dibutyl phosphoric acid on zirconium extraction with diluted tributyl phosphate and the role of uranyl nitrate  

NASA Astrophysics Data System (ADS)

Distribution coefficients of zirconium (DZr) in the 30% TBP — aqueous HNO3 solution extraction system rise 1000 2000 times with the increase of the dibutyl phosphoric acid (HDBP) concentration from 0 to 0.01 0.08 mol/L. A solvate with the molar ratio Zr: HDBP=1 was found by IR spectroscopy and analytic methods in the initial range of HDBP concentration. In the presence of U(VI) DZr decreases with the growing U concentration, however, the ratio of Zr distribution coefficient in the presence of HDBP (DAZr) to DZr determined in its absence, RZr=DAZr/DZr, is rather high. Function of enhancement (F) was introduced for the evaluation of simultaneous influence of U and HDBP on Zr extraction. An increase of the U concentration resulted first in the decrease in FZr, and then in its increase. The rising part of the FZr curve was more noticeable at a molar excess of Zr over HDBP. The mechanism of Zr extraction by 30% TBP solution in the presence of HDBP when Zr is in excess to HDBP indicates the formation of the solvate with the ratio Zr: HDBP=1; in the presence of U(VI) the complex with the same ratio is formed by the HDBP interaction with U in the system with a great excess of both HDBP and Zr.

Blazheva, I. V.; Fedorov, Yu. S.; Zilberman, B. Ya.; Ryabkova, N. V.

2006-01-01

5

Method for calcining nuclear waste solutions containing zirconium and halides  

DOEpatents

A reduction in the quantity of gelatinous solids which are formed in aqueous zirconium-fluoride nuclear reprocessing waste solutions by calcium nitrate added to suppress halide volatility during calcination of the solution while further suppressing chloride volatility is achieved by increasing the aluminum to fluoride mole ratio in the waste solution prior to adding the calcium nitrate.

Newby, Billie J. (Idaho Falls, ID)

1979-01-01

6

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

7

Investigation on Thermal Analysis of Binary Zirconium\\/Oxidant Pyrotechnic Systems  

Microsoft Academic Search

Thermogravimetric analysis (TGA) and differential thermal analysis (DTA) have been used to examine the thermal behavior of powdered zirconium with some pyrotechnic oxidants, in relation to the behavior of the individual constituents. The results showed that decomposition temperature for pure compounds (potassium nitrate, potassium chlorate, potassium perchlorate, barium nitrate and barium peroxide) are 540, 472, 592, 745 and 600°C, respectively.

S. M. Pourmortazavi; S. G. Hosseini; S. S. Hajimirsadeghi; R. Fareghi Alamdari

2008-01-01

8

Studies in zirconium oxidation  

NASA Technical Reports Server (NTRS)

Study provides insight into the oxidation mechanism of zirconium by combining electrical measurements with oxidation data. The measurement of electrical potential across growing scale on zirconium and the determination of conventional weight-change oxidation data were carried out at 550, 700, and 800 degrees C.

Draley, J. E.; Drunen, C. J.; Levitan, J.

1968-01-01

9

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

10

Radiochemical separation of zirconium and hafnium from other radionuclides.  

PubMed

Radiozirconium and radiohafnium may be separated from all other radionuclides except scandium and protactinium by precipitation with mandelic acid from 5-10 M hydrochloric acid, using commercial zirconyl chloride as carrier. Scandium and protactinium are removed by dissolving the precipitate in sodium carbonate, then adding barium nitrate to precipitate barium carbonate which acts as a scavenger. Zirconium mandelate is finally reprecipitated and the sample weighed and counted in this form. The method was checked by analysing commercial zirconyl chloride and standard rock samples for zirconium and hafnium by neutron-activation analysis. PMID:18961201

Hahn, R B

1972-11-01

11

Nitrate and periplasmic nitrate reductases  

PubMed Central

The nitrate anion is a simple, abundant and relatively stable species, yet plays a significant role in global cycling of nitrogen, global climate change, and human health. Although it has been known for quite some time that nitrate is an important species environmentally, recent studies have identified potential medical applications. In this respect the nitrate anion remains an enigmatic species that promises to offer exciting science in years to come. Many bacteria readily reduce nitrate to nitrite via nitrate reductases. Classified into three distinct types – periplasmic nitrate reductase (Nap), respiratory nitrate reductase (Nar) and assimilatory nitrate reductase (Nas), they are defined by their cellular location, operon organization and active site structure. Of these, Nap proteins are the focus of this review. Despite similarities in the catalytic and spectroscopic properties Nap from different Proteobacteria are phylogenetically distinct. This review has two major sections: in the first section, nitrate in the nitrogen cycle and human health, taxonomy of nitrate reductases, assimilatory and dissimilatory nitrate reduction, cellular locations of nitrate reductases, structural and redox chemistry are discussed. The second section focuses on the features of periplasmic nitrate reductase where the catalytic subunit of the Nap and its kinetic properties, auxiliary Nap proteins, operon structure and phylogenetic relationships are discussed. PMID:24141308

Sparacino-Watkins, Courtney; Stolz, John F.; Basu, Partha

2014-01-01

12

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

13

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

14

Surface reactions of tetraneopentyl zirconium on zirconium carbide thin films  

Microsoft Academic Search

Interest has arisen recently in the use of metal alkyl compounds as precursors in the chemical vapor deposition of metal carbides. This paper presents results of a study of the surface chemistry of one such precursor, tetraneopentyl zirconium (ZrNp[sub 4]), on zirconium carbide thin films. Decomposition of the precursor leads to the desorption of both methane and a larger hydrocarbon

John E. Parmeter; D. C. Smith; M. D. Healy

1994-01-01

15

21 CFR 181.33 - Sodium nitrate and potassium nitrate.  

Code of Federal Regulations, 2011 CFR

...2011-04-01 false Sodium nitrate and potassium nitrate. 181.33 Section 181.33 ...Ingredients § 181.33 Sodium nitrate and potassium nitrate. Sodium nitrate and potassium nitrate are subject to prior sanctions...

2011-04-01

16

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 ...Ingredients § 181.33 Sodium nitrate and potassium nitrate. Sodium nitrate and potassium nitrate are subject to prior sanctions...

2010-04-01

17

Nitrate Absorption by Barley  

PubMed Central

The influence of protein synthesis and nitrate reductase activity on nitrate absorption by barley (Hordeum vulgare L.) was investigated. Cycloheximide decreased nitrate absorption. Pretreatment studies showed that cycloheximide affects either energy transfer or nitrate reductase activity or both. Illumination increased plant capacity for nitrate absorption, possibly through increased energy supply and/or increased nitrate reductase activity. There was a positive correlation between nitrate reductase activity and light. Inhibiting the development of nitrate reductase activity by tungstate decreased nitrate absorption. At least two nitrate transport systems are thus proposed in barley: one operating in the dark, with little nitrate reductase activity detectable; and one closely correlated with nitrate reductase activity. Total absorption is the sum of dark absorption and absorption facilitated by nitrate reductase. PMID:16659426

Rao, K. Prasad; Rains, D. William

1976-01-01

18

Organic derivatives of zirconium phosphate  

E-print Network

ORGANIC DERIVATIVES OF ZIRCONIUM PHOSPHATE A Thesis by STEVEN BERYL FINE Submitted to the Graduate College of Texas AAM University in partial fulfillment of the requirement for the degree of MASTER OF SCIENCE December 1980 Major Subject...: Chemistry ORGANIC DERIVATIVES OF ZIRCONIUM PHOSPHATE A Thesis by STEVEN BERYL FINE Approved as to style and content by: Dr. A raham Clearfield (c irman) Dr. Kurt Irgolic (member) 4~~@4 Dr. Martha Scott (member) Dr. C. S. Giam (department head...

Fine, Steven Beryl

1980-01-01

19

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

20

Zirconium mobility in bauxites of Southern Brazil  

Microsoft Academic Search

A geochemical study of the behaviour of zirconium in bauxites developed on alkaline rocks in southern Brazil is presented. Zirconium, generally considered as an immobile element during weathering, shows an important mobility conditioned to the original Zr bearing parent mineral. In the two areas (Poços de Caldas and Lages) zircon is rare and the zirconium bearing parent minerals are complex

A. J. Melfi; F. Subies; D. Nahon; M. L. L. Formoso

1996-01-01

21

Surface reactions of tetraneopentyl zirconium on zirconium carbide thin films  

SciTech Connect

Interest has arisen recently in the use of metal alkyl compounds as precursors in the chemical vapor deposition of metal carbides. This paper presents results of a study of the surface chemistry of one such precursor, tetraneopentyl zirconium (ZrNp[sub 4]), on zirconium carbide thin films. Decomposition of the precursor leads to the desorption of both methane and a larger hydrocarbon species that is tentatively identified as neopentane. The desorption of large amounts of methane may help to explain the fact that ZrC films grown to date with this precursor are not stoichiometric but rather contain excess carbon.

Parmeter, J.E. (Department 1126, Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States)); Smith, D.C.; Healy, M.D. (INC-1, MS-C346, Los Alamos National Laboratory, Los Alamos, New Mexico 87105 (United States))

1994-07-01

22

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

23

Zirconium and hafnium in meteorites  

NASA Technical Reports Server (NTRS)

The abundances of zirconium and hafnium have been determined in nine stony meteorites by a new, precise neutron-activation technique. The Zr/Hf abundance ratios for the chondrites vary in a rather narrow range, consistent with previously published observations from our group. Replicate analyses of new, carefully selected clean interior samples of the Cl chondrite Orgueil yield mean zirconium and hafnium abundances of 5.2 and 0.10 ppm, respectively. These abundances are lower than we reported earlier for two Cl chondrite samples which we now suspect may have suffered contamination. The new Cl zirconium and hafnium abundances are in closer agreement with predictions based on theories of nucleosynthesis than the earlier data.

Ehmann, W. D.; Chyi, L. L.

1974-01-01

24

ZIRCONIUM AND HAFNIUM--2001 86.1 ZIRCONIUM AND HAFNIUM  

E-print Network

are contained in zircon at a ratio of about 50:1. Zircon is a coproduct or byproduct of the mining is processed to produce cubic zirconia, a diamond and colored gemstone simulant. Zirconium metal is used of domestic operations. In 2001, the two domestic zircon producers, which have three mining and processing

25

ZIRCONIUM AND HAFNIUM--2000 87.1 ZIRCONIUM AND HAFNIUM  

E-print Network

in zircon at a ratio of about 50 to 1. Zircon is a coproduct or byproduct of the mining and processing, a diamond and colored gemstone simulant. Zirconium metal is used in nuclear fuel cladding, chemical piping company proprietary data. Domestic production of zircon increased as a heavy-mineral sand mining operation

26

ZIRCONIUM AND HAFNIUM--1999 86.1 ZIRCONIUM AND HAFNIUM  

E-print Network

of the mining and processing of heavy-mineral sands for the titanium minerals, ilmenite and rutile, or tin to produce cubic zirconia, a diamond and colored gemstone simulant. Zirconium is used in nuclear fuel as a recently opened mining operation in Virginia continued to scale-up production. In 1999, production

27

ZIRCONIUM AND HAFNIUM--1998 86.1 ZIRCONIUM AND HAFNIUM  

E-print Network

of the mining and processing of heavy-mineral sands for the titanium minerals, ilmenite and rutile, or tin the diamond simulant, cubic zirconia. Zirconium is used in nuclear fuel cladding, chemical piping in corrosive. Domestic production of zircon increased as a new mine in Virginia came online. Production of milled zircon

28

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

29

Alkali metal nitrate purification  

DOEpatents

A process is disclosed for removing contaminants from impure alkali metal nitrates containing them. The process comprises heating the impure alkali metal nitrates in solution form or molten form at a temperature and for a time sufficient to effect precipitation of solid impurities and separating the solid impurities from the resulting purified alkali metal nitrates. The resulting purified alkali metal nitrates in solution form may be heated to evaporate water therefrom to produce purified molten alkali metal nitrates 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 purified alkali metal nitrates.

Fiorucci, Louis C. (Hamden, CT); Morgan, Michael J. (Guilford, CT)

1986-02-04

30

40 CFR 721.9973 - Zirconium dichlorides (generic).  

Code of Federal Regulations, 2010 CFR

...2010-07-01 2010-07-01 false Zirconium dichlorides (generic). 721.9973...Chemical Substances § 721.9973 Zirconium dichlorides (generic). (a) Chemical...chemical substances identified generically as zirconium dichlorides (PMNs...

2010-07-01

31

Tracing nitrate in watersheds  

NASA Astrophysics Data System (ADS)

Plants need nitrogen to grow, and nitrate is a common fertilizer ingredient, but high levels of nitrate contamination in drinking water sources can cause health problems. It is generally known that nitrogen flows through watersheds from upslope areas down to streams, but the relationships between upslope soil solution or groundwater nitrate concentrations and stream water nitrate levels—and the ways in which land use changes may alter this relationship—are not fully understood.

Balcerak, Ernie

2013-05-01

32

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

33

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

34

Zirconium mobility in bauxites of Southern Brazil  

NASA Astrophysics Data System (ADS)

A geochemical study of the behaviour of zirconium in bauxites developed on alkaline rocks in southern Brazil is presented. Zirconium, generally considered as an immobile element during weathering, shows an important mobility conditioned to the original Zr bearing parent mineral. In the two areas (Poços de Caldas and Lages) zircon is rare and the zirconium bearing parent minerals are complex weathered silicates as "giannettite", eudyalite, astrophyllite, etc. Since the first stages of weathering, zirconium is partially leached of from the bauxite profile and the remaining Zr is incorporated in secondary phases of the bauxite (amorphous ferric oxydes and aluminous goethite).

Melfi, A. J.; Subies, F.; Nahon, D.; Formoso, M. L. L.

1996-07-01

35

Formation of zirconium metallic glass.  

PubMed

Bulk metallic glasses are commonly produced by the rapid cooling of liquid alloys. They have emerged over the past decade as a novel class of materials, with attractive properties and technological promise. The bulk metallic glasses so far produced contain three or more component elements. These complex compositions are necessary to frustrate the crystallization of the liquid melt on cooling, but can also lead to phase separation, which is detrimental to the thermal and mechanical properties of metallic glasses. Here we report, using X-ray diffraction measurements, the formation of a bulk metallic glass from elemental zirconium at high static pressures and low temperatures (relative to its melting temperature at atmospheric pressure). Amorphous zirconium can be recovered at ambient conditions and demonstrates a superior thermal stability compared to amorphous alloys, which could lead to new high-temperature applications of amorphous metals. PMID:15254533

Zhang, Jianzhong; Zhao, Yusheng

2004-07-15

36

Zirconium alloys in nuclear technology  

Microsoft Academic Search

This paper describes the historical development of zirconium and its alloys as structural materials for nuclear reactors.\\u000a The various problems encountered in the early stages of the development of zircaloys and their performance in reactors operating\\u000a presently are described in detail. The development of Zr-2.5 % Nb alloys for pressure tube applications is discussed. The\\u000a paper concludes with a detailed

R. Krishnan; M. K. Asundi

1981-01-01

37

Method for preparing hydrous zirconium oxide gels and spherules  

DOEpatents

Methods for preparing hydrous zirconium oxide spherules, hydrous zirconium oxide gels such as gel slabs, films, capillary and electrophoresis gels, zirconium monohydrogen phosphate spherules, hydrous zirconium oxide spherules having suspendable particles homogeneously embedded within to form a composite sorbent, zirconium monohydrogen phosphate spherules having suspendable particles of at least one different sorbent homogeneously embedded within to form a composite sorbent having a desired crystallinity, zirconium oxide spherules having suspendable particles homogeneously embedded within to form a composite, hydrous zirconium oxide fiber materials, zirconium oxide fiber materials, hydrous zirconium oxide fiber materials having suspendable particles homogeneously embedded within to form a composite, zirconium oxide fiber materials having suspendable particles homogeneously embedded within to form a composite and spherules of barium zirconate. The hydrous zirconium oxide spherules and gel forms prepared by the gel-sphere, internal gelation process are useful as inorganic ion exchangers, catalysts, getters and ceramics.

Collins, Jack L.

2003-08-05

38

Method of making crack-free zirconium hydride  

DOEpatents

Crack-free hydrides of zirconium and zirconium-uranium alloys are produced by alloying the zirconium or zirconium-uranium alloy with beryllium, or nickel, or beryllium and scandium, or nickel and scandium, or beryllium and nickel, or beryllium, nickel and scandium and thereafter hydriding.

Sullivan, Richard W. (Denver, CO)

1980-01-01

39

Nitrated phenols in fog  

NASA Astrophysics Data System (ADS)

Five nitrated phenols and some of their possible photochemical precursors as phenol, cresol and nitrate were identified in fog water from northeastern Bavaria. The concentrations in a rural and an urban area are presented, and the relationships observed between several of the compounds are discussed in terms of gas phase formation mechanisms. The levels of the nitrated phenols (5-300 nmole? -1) and phenol (<10-1000 nmole? -1) in fog were higher than the concentrations reported for rain.

Richartz, Heike; Reischl, Arthur; Trautner, Frank; Hutzinger, Otto

40

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

41

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

42

Drinking Water Problems: Nitrates  

E-print Network

High levels of nitrates in drinking water can be harmful for very young infants and susceptible adults. This publication explains how people are exposed to nitrates, what health effects are caused by them in drinking water and how to remove them....

Dozier, Monty; Melton, Rebecca; Hare, Michael; Hopkins, Janie; Lesikar, Bruce J.

2008-03-28

43

Penta­zirconium 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. PMID:24109256

Balinska, Agnieszka; Tarasiuk, Ivan; Pavlyuk, Volodymyr

2013-01-01

44

Synthesis of zirconium oxide nanoparticle by sol-gel technique  

SciTech Connect

Zirconium oxide nanoparticle is synthesized using sol-gel technique. Various mole ratio of ammonia solution and nitric acid relative to zirconium propoxide is added in the reaction to study the effect on the crystallinity and particle size on zirconium oxide particle. Zirconium oxide synthesized with nitric acid have the smallest particle size under FESEM image and show the increasing formation of crystalline tetragonal phase under XRD diffractogram.

Lim, H. S.; Ahmad, A.; Hamzah, H. [School of Chemical Science and Food Technology, Faculty of Science and Technology, National University of Malaysia, 43600 Bangi (Malaysia)

2013-11-27

45

XPS Studies of the Stability of a Zirconium Carbide Film in the Presence of Zirconium Oxide and Hydrogen  

NASA Astrophysics Data System (ADS)

X-ray photoelectron spectroscopy (XPS) has been used to study the interfacial chemistries of a 65-Å film prepared by depositing zirconium in an oxidizing environment onto a methane-pretreated 11-Å thick zirconium oxide film, which initially was deposited onto a gold substrate. The second metal deposition results in an outermost region composed of a mixed zirconium oxide, while below there is metallic zirconium followed by zirconium carbide and carbon on top of the first zirconium oxide film, which is itself in contact with the gold. The carbide component showed no changes on heating to 425°C, on treating with a hydrogen plasma at room temperature, or on heating the resulting film to 425°C. The oxide layers do show characteristic changes, and this also contrasts with earlier observations for a zirconium sulphide film. The zirconium carbide Zr3d5/2 component has a binding energy of 180.6 eV.

Wong, P. C.; Li, Y. S.; Mitchell, K. A. R.

46

Industrial applications of titanium and zirconium: Fourth volume  

SciTech Connect

This book presents industrial applications of titanium and zirconium. This book also contains information on other reactive and refractory metals, including niobium, tantalum, and hafnium. There are fourteen (14) peer-reviewed papers which target these subjects: the applications of titanium; the applications of zirconium and other reactive metals and the technology of titanium and zirconium.

Young; Durham

1986-01-01

47

The chemical vapor deposition of zirconium carbide onto ceramic substrates  

Microsoft Academic Search

Zirconium carbide is an attractive ceramic material due to its unique properties such as high melting point, good thermal conductivity, and chemical resistance. The controlled preparation of zirconium carbide films of superstoichiometric, stoichiometric, and substoichiometric compositions has been achieved utilizing zirconium tetrachloride and methane precursor gases in an atmospheric pressure high temperature chemical vapor deposition system.

Glass John A Jr; Palmisiano Nick Jr; R. Edward Welsh

1999-01-01

48

Synthesis of nanosized zirconium carbide by laser pyrolysis route  

Microsoft Academic Search

Nanosized zirconium carbide was obtained by carburization of tetragonal zirconia\\/free carbon nanocomposites synthesized by laser pyrolysis technique using zirconium butoxide as precursor and ethylene as sensitizer gas. To achieve the carboreduction, the powder had to be annealed at high temperature under Ar atmosphere to reduce the oxygen and form zirconium carbide (ZrC). Different temperatures were investigated for the heat treatment

L. Combemale; Y. Leconte; X. Portier; N. Herlin-Boime; C. Reynaud

2009-01-01

49

The chemical vapor deposition of zirconium carbide onto ceramic substrates  

SciTech Connect

Zirconium carbide is an attractive ceramic material due to its unique properties such as high melting point, good thermal conductivity, and chemical resistance. The controlled preparation of zirconium carbide films of superstoichiometric, stoichiometric, and substoichiometric compositions has been achieved utilizing zirconium tetrachloride and methane precursor gases in an atmospheric pressure high temperature chemical vapor deposition system.

Glass, John A, Jr.; Palmisiano, Nick, Jr.; Welsh, R. Edward

1999-07-01

50

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

51

VACUUM PUMPING STUDY OF TITANIUM-ZIRCONIUM-VANADIUM THIN FILMS*  

E-print Network

ERL 03-8 VACUUM PUMPING STUDY OF TITANIUM-ZIRCONIUM-VANADIUM THIN FILMS* Yulin Li# and Simon Ho performance of Titanium- Zirconium-Vanadium (TiZrV) NEG thin films was investigated to provide `engineering- Zirconium-Vanadium (TiZrV) NEG thin films, deposited on the interior of stainless steel (SST) pipes. The Ti

52

46 CFR 148.205 - Ammonium nitrate and ammonium nitrate fertilizers.  

Code of Federal Regulations, 2014 CFR

...Ammonium nitrate and ammonium nitrate fertilizers. 148.205 Section 148.205 ...Ammonium nitrate and ammonium nitrate fertilizers. (a) This section applies to...of ammonium nitrate and the following fertilizers composed of uniform,...

2014-10-01

53

46 CFR 148.205 - Ammonium nitrate and ammonium nitrate fertilizers.  

Code of Federal Regulations, 2012 CFR

...Ammonium nitrate and ammonium nitrate fertilizers. 148.205 Section 148.205 ...Ammonium nitrate and ammonium nitrate fertilizers. (a) This section applies to...of ammonium nitrate and the following fertilizers composed of uniform,...

2012-10-01

54

46 CFR 148.205 - Ammonium nitrate and ammonium nitrate fertilizers.  

Code of Federal Regulations, 2011 CFR

...Ammonium nitrate and ammonium nitrate fertilizers. 148.205 Section 148.205 ...Ammonium nitrate and ammonium nitrate fertilizers. (a) This section applies to...of ammonium nitrate and the following fertilizers composed of uniform,...

2011-10-01

55

46 CFR 148.205 - Ammonium nitrate and ammonium nitrate fertilizers.  

Code of Federal Regulations, 2013 CFR

...Ammonium nitrate and ammonium nitrate fertilizers. 148.205 Section 148.205 ...Ammonium nitrate and ammonium nitrate fertilizers. (a) This section applies to...of ammonium nitrate and the following fertilizers composed of uniform,...

2013-10-01

56

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

57

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  

NASA Astrophysics Data System (ADS)

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 of the catalyst was evaluated by monitoring the photocatalytic decolorization of methyl orange under visible light irradiation. The results showed that the activities of Zr-I-TiO2 catalysts were higher than that of TiO2 doped with iodine alone (I-TiO2), and the optimal doping concentration in the Zr-I-TiO2 calcined at 400 °C was determined to be about 0.05 (molar ratio of Zr:Ti). In addition, the photocatalytic activity of Zr-I-TiO2 calcined at 400 °C was found to be significantly higher than that calcined at 500 or 600 °C. Based on the physico-chemical characterization, we concluded that the role of zirconium on the I-TiO2 surface is to increase the number of reactive sites by generating a small crystal size and large surface area. The inhibition of electron-hole pair recombination, by trapping photo-generated electrons with Zr4+, did not contribute markedly to the improved photocatalytic activity of Zr-I-TiO2.

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

2011-09-01

58

Superconductivity in zirconium-rhodium alloys  

NASA Technical Reports Server (NTRS)

Metallographic studies and transition temperature measurements were made with isothermally annealed and water-quenched zirconium-rhodium alloys. The results clarify both the solid-state phase relations at the Zr-rich end of the Zr-Rh alloy system and the influence upon the superconducting transition temperature of structure and composition.

Zegler, S. T.

1969-01-01

59

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

60

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

61

Some History of Nitrates  

NASA Astrophysics Data System (ADS)

The history of saltpeter is an interesting combination of chemistry, world trade, technology, politics, and warfare. Originally it was obtained from the dirt floors of stables, sheep pens, pigeon houses, caverns, and even peasants' cottages; any place manure and refuse accumulated in soil under dry conditions. When these sources became inadequate to meet demand it was manufactured on saltpeter plantations, located in dry climates, where piles of dirt, limestone, and manure were allowed to stand for three to five years while soil microbes oxidized the nitrogen to nitrate—an example of early bioengineering. Extensive deposits of sodium nitrate were mined in the Atacama Desert in northern Chile from 1830 until the mid 1920s when the mines were displaced by the Haber Ostwald process.

Barnum, Dennis W.

2003-12-01

62

40 CFR 471.90 - Applicability; description of the zirconium-hafnium forming subcategory.  

Code of Federal Regulations, 2010 CFR

... Applicability; description of the zirconium-hafnium forming subcategory. 471...METAL POWDERS POINT SOURCE CATEGORY Zirconium-Hafnium Forming Subcategory § 471.90 Applicability; description of the zirconium-hafnium forming subcategory....

2010-07-01

63

40 CFR 421.330 - Applicability: Description of the primary zirconium and hafnium subcategory.  

Code of Federal Regulations, 2010 CFR

...Applicability: Description of the primary zirconium and hafnium subcategory. 421.330...MANUFACTURING POINT SOURCE CATEGORY Primary Zirconium and Hafnium Subcategory § 421.330 Applicability: Description of the primary zirconium and hafnium subcategory. The...

2010-07-01

64

40 CFR 721.10089 - Modified salicylic acid, zirconium complex (generic).  

Code of Federal Regulations, 2010 CFR

...2010-07-01 false Modified salicylic acid, zirconium complex (generic...Substances § 721.10089 Modified salicylic acid, zirconium complex (generic...identified generically as modified salicylic acid, zirconium complex (PMN...

2010-07-01

65

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...

66

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...

67

ZIRCONIUM AND HAFNIUM (Data in metric tons unless otherwise noted)  

E-print Network

industries. Salient Statistics--United States: 2006 2007 2008 2009 2010 e Production, zircon (ZrO2 content) W W W W W Imports: Zirconium, ores and concentrates (ZrO2 content) 23,500 13,000 22,300 9,370 11: Zirconium ores and concentrates (ZrO2 content) 49,600 43,000 27,400 25,700 34,000 Zirconium, unwrought

68

ZIRCONIUM AND HAFNIUM (Data in metric tons, unless otherwise noted)  

E-print Network

other companies as well. Zirconia (ZrO2) was produced from zircon sand at plants in Alabama, New (ZrO2 content)1 W W W W W Imports: Zirconium, ores and concentrates (ZrO2 content) 60,800 60,100 40,600 58,200 38,600 Zirconium, alloys, waste and scrap (ZrO2 content) 884 836 929 1,210 1,400 Zirconium

69

ZIRCONIUM AND HAFNIUM (Data in metric tons unless otherwise noted)  

E-print Network

Imports: Zirconium, ores and concentrates (ZrO2 content) 9,370 14,900 17,200 16,700 6,500 Zirconium, unwrought, powder, and waste and scrap 5 8 10 23 10 Exports: Zirconium ores and concentrates (ZrO2 content, apparent (ZrO2 content) W W W W W Prices: Zircon, dollars per metric ton (gross weight): Domestic 1 830 860

70

ZIRCONIUM AND HAFNIUM (Data in metric tons unless otherwise noted)  

E-print Network

industries. Salient Statistics--United States: 2008 2009 2010 2011 2012 e Production, zircon (ZrO2 content) W W W W W Imports: Zirconium, ores and concentrates (ZrO2 content) 22,300 9,370 14,900 17,200 26 Exports: Zirconium ores and concentrates (ZrO2 content) 27,400 25,700 30,800 15,800 21,000 Zirconium

71

ZIRCONIUM AND HAFNIUM (Data in metric tons unless otherwise noted)  

E-print Network

industries. Salient Statistics--United States: 2007 2008 2009 2010 2011 e Production, zircon (ZrO2 content) W W W W W Imports: Zirconium, ores and concentrates (ZrO2 content) 13,000 22,300 9,370 14,900 13 Exports: Zirconium ores and concentrates (ZrO2 content) 43,000 27,400 25,700 30,800 15,500 Zirconium

72

ZIRCONIUM AND HAFNIUM (Data in metric tons unless otherwise noted)  

E-print Network

zirconium chemicals were produced by 10 other companies. Zirconia (ZrO2) was produced from zircon at plants Statistics--United States: 2002 2003 2004 2005 2006e Production, zircon (ZrO2 content) W W W W W Imports: Zirconium, ores and concentrates (ZrO2 content) 22,900 24,300 22,900 24,800 17,500 Zirconium, unwrought

73

ZIRCONIUM AND HAFNIUM (Data in metric tons unless otherwise noted)  

E-print Network

. Secondary zirconium chemicals were produced by 10 other companies. Zirconia (ZrO2) was produced from zircon 2003 2004 2005e Production, zircon (ZrO2 content) W W W W W Imports: Zirconium, ores and concentrates (ZrO2 content) 39,400 22,900 24,300 22,900 19,400 Zirconium, unwrought, powder, and waste and scrap

74

49 CFR 176.415 - Permit requirements for Division 1.5, ammonium nitrates, and certain ammonium nitrate fertilizers.  

Code of Federal Regulations, 2012 CFR

...nitrates, and certain ammonium nitrate fertilizers. 176.415 Section 176.415 ...nitrates, and certain ammonium nitrate fertilizers. (a) Except as provided in...Ammonium nitrate UN1942, ammonium nitrate fertilizers containing more than 70%...

2012-10-01

75

49 CFR 176.415 - Permit requirements for Division 1.5, ammonium nitrates, and certain ammonium nitrate fertilizers.  

Code of Federal Regulations, 2013 CFR

...nitrates, and certain ammonium nitrate fertilizers. 176.415 Section 176.415 ...nitrates, and certain ammonium nitrate fertilizers. (a) Except as provided in...Ammonium nitrate UN1942, ammonium nitrate fertilizers containing more than 70%...

2013-10-01

76

49 CFR 176.415 - Permit requirements for Division 1.5, ammonium nitrates, and certain ammonium nitrate fertilizers.  

Code of Federal Regulations, 2014 CFR

...nitrates, and certain ammonium nitrate fertilizers. 176.415 Section 176.415 ...nitrates, and certain ammonium nitrate fertilizers. (a) Except as provided in...Ammonium nitrate UN1942, ammonium nitrate fertilizers containing more than 70%...

2014-10-01

77

49 CFR 176.415 - Permit requirements for Division 1.5, ammonium nitrates, and certain ammonium nitrate fertilizers.  

Code of Federal Regulations, 2011 CFR

...nitrates, and certain ammonium nitrate fertilizers. 176.415 Section 176.415 ...nitrates, and certain ammonium nitrate fertilizers. (a) Except as provided in...Ammonium nitrate UN1942, ammonium nitrate fertilizers containing more than 70%...

2011-10-01

78

Polarographic determination of zirconium at trace level.  

PubMed

An indirect polarographic method has been developed for the determination of zirconium by formation of molybdozirconophosphoric acid, its extraction with MIBK or a mixture of diethyl ether and 1-butanol, stripping with alkali and measurement of the Mo(VI) by its catalytic effect on the polarographic reduction of hydrogen peroxide. Depending on the extradant, a detection limit of 2.5 or 8.9 mu/gl, can be achieved. PMID:18963868

Castrillejo, Y; Pardo, R; Barrado, E; Batanero, P S

1985-05-01

79

Irradiation growth of zirconium single crystals  

NASA Astrophysics Data System (ADS)

Irradiation growth of zirconium single crystals has been studied during neutron irradiation at 353 K and 553 K at fluences up to 2× 10 25 n/m 2. The results may be summarized as follows: (a) there was an expansion parallel to the a-axis and a c-axis contraction; (b) the growth strains were small (~10 -4), (c) growth saturated at fluences less than ~5× 10 24 n/m 2, (d) the growth behaviour was only weakly dependent on temperature for the range studied, (e) there was a calculated volume increase of the same order as the growth strain, and (f) single crystals prepared from stock of iodide and zone-refined purity showed similar growth behaviour at 553 K. The a-axis expansion is attributed to the annihilation of an excess of interstitials at < a>-type dislocations and interstitial loops. The c-axis contraction may be caused by: (1) elastic relaxation around vacancies or small vacancy clusters, (2) non-linear elastic effects at the dislocation cores of small < a>-type loops, or (3) sub-microscopic vacancy loops with < c>-component Burgers vectors. Comparison with data from polycrystalline zirconium confirms that grain boundaries can play an important role in the irradiation growth of zirconium.

Carpenter, G. J. C.; Murgatroyd, R. A.; Rogerson, A.; Watters, J. F.

1981-10-01

80

High temperature behavior of zirconium germanates  

SciTech Connect

The high temperature behavior of zirconium germanates ZrGeO{sub 4} and Zr{sub 3}GeO{sub 8} up to 2300 °C has been studied using the original photoemission thermal analysis technique with the comprehensive physicochemical study of solid and gaseous intermediate and final products. The two-stage process of incongruent sublimation of GeO{sub 2} was established and the phase boundary of the homogeneity range for ZrGeO{sub 4} and Zr{sub 3}GeO{sub 8} were deduced from the thermal analysis, X-ray diffraction and Raman spectroscopy studies. A high tendency to sintering of the final ZrO{sub 2} product is discussed. - Graphical abstract: The decomposition of zirconium germanates leads to the formation of gaseous GeO{sub 2} and solid sintered ZrO{sub 2} and occurs via two stages with the formation of intermediate ZrO{sub 2}-rich solid solution. - Highlights: ?Thermal behavior of ZrGeO{sub 4} and Zr{sub 3}GeO{sub 8} was studied using the original thermal analysis technique in wide temperature range. ?The decomposition occurs via two stages with the formation of intermediate ZrO{sub 2}-rich solid solution. ?The decomposition of zirconium germanates leads to the formation of gaseous GeO{sub 2} and solid sintered ZrO{sub 2}. ?The temperature of decomposition is strongly depended on the total gas pressure.

Utkin, A.V., E-mail: utkinalex@hotmail.com [Institute of Solid State Chemistry and Mechanochemistry SB RAS, 18 Kutateladze st., Novosibirsk 630128 (Russian Federation); Baklanova, N.I. [Institute of Solid State Chemistry and Mechanochemistry SB RAS, 18 Kutateladze st., Novosibirsk 630128 (Russian Federation); Vasilyeva, I.G. [Nikolaev Institute of Inorganic Chemistry SB RAS, 3 Acad. Lavrentiev ave, Novosibirsk 630090 (Russian Federation)

2013-05-15

81

Nitrate and Prussic Acid Poisoning  

E-print Network

fertilized can accumu- late toxic levels. Turning cattle into holding pens or corrals full of manure with carelessweeds or grasses can result in immediate poisoning. Nitrates do not accumulate when there is nor- mal rainfall or irrigation. Under those.... Nitrate accumulates and is stored in lower leaves and stems, ready for the plant to mobilize and use when rapid growth resumes. Nitrate levels can change from day to day and even from morning until evening. Small grains can accumulate toxic levels...

Stichler, Charles; Reagor, John C.

2001-09-05

82

Lithium-boron anodes in nitrate thermal battery cells  

Microsoft Academic Search

A thermally activated electrochemical cell utilizes a lithium-boron anode and a molten nitrate electrolyte selected from the group consisting of lithium nitrate, a mixture of lithium nitrate and sodium nitrate, a mixture of lithium nitrate and potassium nitrate, and a mixture of lithium nitrate and sodium nitrate with potassium nitrate, to provide improved cell electrical performance. The electrolyte is contained

G. E. McManis; A. N. Fletcher; M. H. Miles

1985-01-01

83

Molecular Control of Nitrate Reductase and Other Enzymes Involved in Nitrate Assimilation  

Microsoft Academic Search

Nitrate acts as both a nutrient and a signal in plants. Nitrate induces gene expression of enzymes for its metabolism into amino acids but also has other effects on plant metabolism and development. Familiar nitrate-induced enzymes are nitrate and nitrite reductases, nitrate transporters, glutamine synthetase, glutamate synthase, ferredoxin and ferredoxin NADP+ reductase. Microarray analysis of nitrate-stimulated gene expression has identified

Wilbur H. Campbell

84

21 CFR 172.160 - Potassium nitrate.  

Code of Federal Regulations, 2011 CFR

... 2011-04-01 2011-04-01 false Potassium nitrate. 172.160 Section 172.160...CONSUMPTION Food Preservatives § 172.160 Potassium nitrate. The food additive potassium nitrate may be safely used as a curing...

2011-04-01

85

76 FR 47238 - Ammonium Nitrate From Russia  

Federal Register 2010, 2011, 2012, 2013, 2014

...Second Review] Ammonium Nitrate From Russia Determination On the basis of the record...antidumping duty order on ammonium nitrate from Russia would be likely to lead to continuation...2011), entitled Ammonium Nitrate from Russia: Investigation No....

2011-08-04

86

76 FR 11273 - Ammonium Nitrate From Russia  

Federal Register 2010, 2011, 2012, 2013, 2014

...Second Review)] Ammonium Nitrate From Russia AGENCY: United States International Trade...investigation on ammonium nitrate from Russia...investigation on ammonium nitrate from Russia would be likely to lead to...

2011-03-01

87

21 CFR 172.160 - Potassium nitrate.  

Code of Federal Regulations, 2010 CFR

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

2010-04-01

88

Nitrate Removal in NITREXTM Permeable Reactive Barriers  

E-print Network

Nitrate Removal in NITREXTM Permeable Reactive Barriers: Investigating Denitrification Using a 15 (particularly of nitrate) to aquatic systems is a growing problem. The NITREXTM Permeable Reactive Barrier (PRB removal processes is at work. KEYWORDS: nitrate removal, denitrification, permeable reactive barrier

Vallino, Joseph J.

89

Properties of polymeric zirconium phosphates as Friedel-Crafts catalysts  

Microsoft Academic Search

The activities of some amorphous and crystalline polymeric zirconium phosphates as Friedel-Crafts catalysts have been investigated. Catalytic behaviour was studied in the alkylation of anisole with alcohols in both liquid and gas phases and compared with the activity of alumina and acid activated clay. Under comparable experimental conditions, the catalytic activity of amorphous zirconium phosphate compares favourably with that shown

M. Conceição Cruz Costa; Robert A. W. Johnstone; David Whittaker

1995-01-01

90

Zirconium metal matrix-silicon carbide composite nuclear reactor components  

Microsoft Academic Search

In a nuclear reactor having metallic components, the improvement is described wherein at least one metallic component is a composite metallic component. The composite metallic component comprises a member formed from 90-60 volume percent of a metal matrix of a metal selected from the group consisting essentially of zirconium and a zirconium alloy containing less than about 5 percent by

1987-01-01

91

Nitrates in congestive heart failure  

Microsoft Academic Search

Nitrates are commonly used in the therapy of congestive heart failure (CHF). They exert beneficial hemodynamic effects by decreasing left ventricular filling pressure and systemic vascular resistance while modestly improving cardiac output. The improvement in left ventricular function caused by nitrates is the result of combined reduction in outflow resistance and mitral regurgitation, while decreased pericardial constraint and subendocardial ischemia

Jocelyn Dupuis

1994-01-01

92

Mechanism for zirconium oxide atomic layer deposition using bis,,methylcyclopentadienyl...methoxymethyl zirconium  

E-print Network

Zirconium oxide ZrO2 is a promising high-dielectric constant replacement for SiO2 in future microelectronic for preparing ZrO2 thin films because it affords precise thick- ness control and superb conformality.5, ab initio calculations are performed to predict the order in which the ligands are lost during ZrO2

93

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

94

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

95

Short-time oxidation of zirconium.  

NASA Technical Reports Server (NTRS)

Study of zirconium oxidation kinetics for maximum exposure times of 3 min and in the temperature range 440 to 850 C. 'Discontinuous' oxidation runs were employed whereby a specimen was inserted into the gas stream for a predetermined time, removed and weighed, and reinserted into the oxidation atmosphere. It is considered that the increase in the observed activation energy for the early stage parabolic oxidation is a manifestation of a change from an n-type oxide to a predominantly p-type oxide, in agreement with the authors' earlier conclusion (1971) based on pressure effects.

Srivastava, L. P.; Archbold, T. F.

1972-01-01

96

Cherenkov and Scintillation Properties of Cubic Zirconium  

NASA Technical Reports Server (NTRS)

Cubic zirconium (CZ) is a high index of refraction (n =2.17) material that we have investigated for Cherenkov counter applications. Laboratory and proton accelerator tests of an 18cc sample of CZ show that the expected fast Cherenkov response is accompanied by a longer scintillation component that can be separated by pulse shaping. This presents the possibility of novel particle spectrometers which exploits both properties of CZ. Other high index materials being examined for Cherenkov applications will be discussed. Results from laboratory tests and an accelerator exposure will be presented and a potential application in solar energetic particle instruments will be discussed

Christl, M.J.; Adams, J.H.; Parnell, T.A.; Kuznetsov, E.N.

2008-01-01

97

Creep Behavior of Hydrogenated Zirconium Alloys  

NASA Astrophysics Data System (ADS)

Zirconium (Zr) alloys are the primary structural materials of most water reactors. Creep is considered to be one of the important degradation mechanisms of Zr alloys during reactor operating and repository conditions. Zr alloys pick up hydrogen (H2) during their service from the coolant water. Hydrogen can be present in solid solution or precipitated hydride form in Zr alloys depending upon the temperature and concentration. This study reviews the effect of hydrogen on creep behavior of Zr alloys used in the water reactors.

Sarkar, A.; Boopathy, K.; Eapen, J.; Murty, K. L.

2014-10-01

98

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

99

Studies of nitrate reductase in marine phytoplankton  

Microsoft Academic Search

Certain marine phytoplankton contain the enzyme nitrate rcductase when growing on nitrate, but only low levels of enzyme were found during growth with ammonium or when the nitrogen source was depleted. Netted samples of oceanic phytoplankton contained the enzyme when taken from waters with nitrate concentrations 2-10 PM. Ammonium was assimilated in preference to nitrate in phytoplankton cultures supplied with

R. W. EPPLEY; J. L. COATSWORTH; LUCIA SOLÓRZANO

1969-01-01

100

Nitrate Utilization by the Diatom Skeletonema costatum  

PubMed Central

Nitrate utilization has been characterized in nitrogen-deficient cells of the marine diatom Skeletonema costatum. In order to separate nitrate uptake from nitrate reduction, nitrate reductase activity was suppressed with tungstate. Neither nitrite nor the presence of amino acids in the external medium or darkness affects nitrate uptake kinetics. Ammonium strongly inhibits carrier-mediated nitrate uptake, without affecting diffusion transfer. A model is proposed for the uptake and assimilation of nitrate in S. costatum and their regulation by ammonium ions. PMID:16660653

Serra, Juan L.; Llama, Maria J.; Cadenas, Eduardo

1978-01-01

101

Iron chlorosis and nitrate reductase activity in response to Fe stress and additional nitrate in sorghum  

Microsoft Academic Search

Effect of additional nitrate supply on chlorosis development at different levels of Fe stress was examined in iron efficient and inefficient sorghum cultivars. Nitrate reductase, the enzyme primarily responsible for nitrate reduction was estimated in roots and leaves as affected by Fe stress and additional nitrate.Young leaves showed differences in chlorosis progression at Fe stress levels. Nitrate reductase activity was

D. P. Pandey

1989-01-01

102

Ballistic effectiveness of superdense solid composite propellants with zirconium or zirconium hydride  

NASA Astrophysics Data System (ADS)

The ballistic effectiveness of propellants depends not only on the value of specific impulse but also on many other performances, primarily on the density. Despite the density itself does not enter the expression of the rocket velocity (W = Isp ln(Mlaunch/Mfinish) where Mlaunch and Mfinish are the rocket launch mass and its mass after the propellant is burnt, respectively), it in§uences the value Mlaunch/Mfinish of the specific rocket. If one charges the construction of fixed volume with a more dense propellant, the ratio Mlaunch/Mfinish increases and, consequently, W increases as well. In this paper, the possibility of creating solid composite propellants (SCP) with zirconium (density 6.49 g/cm3) and zirconium hydride (density 5.61 g/cm3 ) as energetic compounds instead of aluminum is considered. It was found for what kinds of engines these propellants have to be more effective than propellants based on aluminum.

Lempert, D.; Manelis, G.; Nechiporenko, G.

2011-10-01

103

Nitrate transport is independent of NADH and NAD(P)H nitrate reductases in barley seedlings  

NASA Technical Reports Server (NTRS)

Barley (Hordeum vulgare L.) has NADH-specific and NAD(P)H-bispecific nitrate reductase isozymes. Four isogenic lines with different nitrate reductase isozyme combinations were used to determine the role of NADH and NAD(P)H nitrate reductases on nitrate transport and assimilation in barley seedlings. Both nitrate reductase isozymes were induced by nitrate and were required for maximum nitrate assimilation in barley seedlings. Genotypes lacking the NADH isozyme (Az12) or the NAD(P)H isozyme (Az70) assimilated 65 or 85%, respectively, as much nitrate as the wild type. Nitrate assimilation by genotype (Az12;Az70) which is deficient in both nitrate reductases, was only 13% of the wild type indicating that the NADH and NAD(P)H nitrate reductase isozymes are responsible for most of the nitrate reduction in barley seedlings. For all genotypes, nitrate assimilation rates in the dark were about 55% of the rates in light. Hypotheses that nitrate reductase has direct or indirect roles in nitrate uptake were not supported by this study. Induction of nitrate transporters and the kinetics of net nitrate uptake were the same for all four genotypes indicating that neither nitrate reductase isozyme has a direct role in nitrate uptake in barley seedlings.

Warner, R. L.; Huffaker, R. C.

1989-01-01

104

Nucleation Pathways For Freezing Of Two Grades Of Zirconium  

NASA Technical Reports Server (NTRS)

Report discusses classical nucleation theory of freezing and describes experimental study of nucleation mechanisms that predominate during freezing of spherical specimens of initially molten zirconium levitated electrostatically in vacuum.

Rhim, Won-Kyu; Rulison, Aaron; Bayuzick, Robert; Hofmeister, William; Morton, Craig

1996-01-01

105

First principles modeling of zirconium solution in bulk UO2  

NASA Astrophysics Data System (ADS)

We modeled the solution behavior of zirconium in uranium dioxide (UO2) by using density functional theory. The Coulomb repulsion of uranium 5f elections was characterized by a spherically averaged Hubbard parameter. Our results indicate that zirconium prefers to locate at U vacancies in UO2 and presents a slight tendency to accumulate in thermodynamics. The solution energies for hcp Zr metal and monoclinic ZrO2 indicates that these two precipitates are insoluble in UO2. In perfect UO2, the band-gap opening is governed by U 5f peaks around the Fermi energy, whereas the solution of zirconium further leads to the band gap splitting owing to the introduction of zirconium 4d peaks especially at high defect concentrations.

Lan, Jian-Hui; Wang, Lin; Li, Shuo; Yuan, Li-Yong; Feng, Yi-Xiao; Sun, Wei; Zhao, Yu-Liang; Chai, Zhi-Fang; Shi, Wei-Qun

2013-05-01

106

Investigation of Electrochemical Recovery of Zirconium from Spent Nuclear Fuels  

SciTech Connect

This project uses both modeling and experimental studies to design optimal electrochemical technology methods for recovery of zirconium from used nuclear fuel rods for more effective waste management. The objectives are to provide a means of efficiently separating zirconium into metallic high-level waste forms and to support development of a process for decontamination of zircaloy hulls to enable their disposal as low- and intermediate-level waste. Modeling work includes extension of a 3D model previously developed by Seoul National University for uranium electrorefining by adding the ability to predict zirconium behavior. Experimental validation activities include tests for recovery of zirconium from molten salt solutions and aqueous tests using surrogate materials. *This is a summary of the FY 2013 progress for I-NERI project # 2010-001-K provided to the I-NERI office.

Michael Simpson; II-Soon Hwang

2014-06-01

107

Electrochemical study of corrosion phenomena in zirconium alloys  

E-print Network

Shadow corrosion of zirconium alloy fuel cladding in BWR environments, the phenomenon in which accelerated corrosion is experienced when the cladding surface is in close proximity to other metals, has become a potentially ...

Treeman, Nicole M

2005-01-01

108

Fatigue behavior of alpha-zirconium phosphate/epoxy nanocomposites  

E-print Network

Fatigue crack growth in ±-Zirconium phosphate/epoxy nanocomposites was investigated. A new fatigue testing technique was implemented for miniature samples. Two different methods ?strength of materials and Rayleigh-Ritz - were used in determining...

Varadharajan, Balaji R.

2006-04-12

109

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

Code of Federal Regulations, 2010 CFR

...silylmethyl-, hydrolysis products with alkanol zirconium(4+) salt and silica, acetates...silylmethyl-, hydrolysis products with alkanol zirconium(4+) salt and silica, acetates...hydrolysis products with alkanol zirconium(4+) salt and silica,...

2010-07-01

110

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

Code of Federal Regulations, 2014 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...

2014-07-01

111

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

112

Zirconium Hydride Space Power Reactor design.  

NASA Technical Reports Server (NTRS)

The Zirconium Hydride Space Power Reactor being designed and fabricated at Atomics International is intended for a wide range of potential applications. Throughout the program a series of reactor designs have been evaluated to establish the unique requirements imposed by coupling with various power conversion systems and for specific applications. Current design and development emphasis is upon a 100 kilowatt thermal reactor for application in a 5 kwe thermoelectric space power generating system, which is scheduled to be fabricated and ground tested in the mid 70s. The reactor design considerations reviewed in this paper will be discussed in the context of this 100 kwt reactor and a 300 kwt reactor previously designed for larger power demand applications.

Asquith, J. G.; Mason, D. G.; Stamp, S.

1972-01-01

113

Plastic deformation of polycrystalline zirconium carbide  

NASA Technical Reports Server (NTRS)

The compressive yield strength of arc-melted polycrystalline zirconium carbide has been found to vary from 77 kg per sq mm at 1200 C to 19 kg per sq mm at 1800 C. Yield drops were observed with plastic strain-rates greater than 0.003/sec but not with slower strain rates. Strain-rate change experiments yielded values for the strain-rate sensitivity parameter m which range from 6.5 at 1500 C to 3.8 at 1800 C, and the product dislocation velocity stress exponent times T was found to decrease linearly with increasing temperature. The deformation rate results are consistent with the Kelly-Rowcliffe model in which the diffusion of carbon assists the motion of dislocations.

Darolia, R.; Archbold, T. F.

1976-01-01

114

Temperature dependence of damage accumulation in ?-zirconium  

NASA Astrophysics Data System (ADS)

Using the input data obtained from molecular dynamics (MD) simulations on defect energetics and cascade damage, we present results obtained on irradiation of hexagonal-close-packed (hcp) ?-zirconium under different conditions with a kinetic Monte Carlo (kMC) model. We used three 25 keV cascade databases at temperatures of 100 K, 300 K and 600 K respectively. The evolution of the microstructure during irradiation for a dose rate of 10 -6 dpa/s, at temperatures of 100 K, 300 K and 600 K until a final dose of 0.1 dpa has been studied. We have considered isotropic motion for vacancies and one dimensional movement for interstitials and we have studied how the accumulation of damage is affected considering different temperatures. We present preliminary comparisons with experimental data.

Arévalo, C.; Caturla, M. J.; Perlado, J. M.

2007-08-01

115

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

116

ZIRCONIUM AND HAFNIUM (Data in metric tons unless otherwise noted)  

E-print Network

were produced by the metal producer in Oregon and by at least 11 other companies. Zirconia (ZrO2, zircon (ZrO2 content) W W W W W Imports: Zirconium, ores and concentrates (ZrO2 content) 22,900 24,800 23 4 4 4 4 10 Exports: Zirconium ores and concentrates (ZrO2 content) 44,700 65,600 49,600 43,000 34

117

ZIRCONIUM AND HAFNIUM (Data in metric tons, unless otherwise noted)  

E-print Network

produced by 10 other companies. Zirconia (ZrO2) was produced from zircon sand at plants in Alabama, New (ZrO2 content)1 100,000 100,000 100,000 100,000 100,000 Imports: Zirconium, ores and concentrates (ZrO2 content) 60,100 40,600 58,200 37,500 42,600 Zirconium, alloys, waste and scrap (ZrO2 content) 836

118

ZIRCONIUM AND HAFNIUM (Data in metric tons, unless otherwise noted)  

E-print Network

chemicals were produced by 10 other companies. Zirconia (ZrO2) was produced from zircon sand at plants 2002e Production, zircon (ZrO2 content)1 100,000 100,000 100,000 100,000 100,000 Imports: Zirconium, ores and concentrates (ZrO2 content) 58,200 37,500 42,400 39,400 20,900 Zirconium, alloys, waste

119

ZIRCONIUM AND HAFNIUM (Data in metric tons unless otherwise noted)  

E-print Network

other companies. Zirconia (ZrO2) was produced from zircon sand at plants in Alabama, New Hampshire, New (ZrO2 content) W W W W W Imports: Zirconium, ores and concentrates (ZrO2 content) 42,400 39,400 22,900 24,300 20,300 Zirconium, alloys, waste and scrap, and powder (ZrO2 content) 1,400 850 750 308 278

120

ZIRCONIUM AND HAFNIUM (Data in metric tons unless otherwise noted)  

E-print Network

were produced by the metal producer in Oregon and by at least 11 other companies. Zirconia (ZrO2, zircon (ZrO2 content) W W W W W Imports: Zirconium, ores and concentrates (ZrO2 content) 24,300 22,900 24 5 4 4 4 4 Exports: Zirconium ores and concentrates (ZrO2 content) 45,900 44,700 65,600 49,600 48

121

ZIRCONIUM AND HAFNIUM (Data in metric tons unless otherwise noted)  

E-print Network

were produced by the metal producer in Oregon and by at least 10 other companies. Zirconia (ZrO2, zircon (ZrO2 content) W W W W W Imports: Zirconium, ores and concentrates (ZrO2 content) 24,800 23,500 13 and scrap 4 4 4 12 5 Exports: Zirconium ores and concentrates (ZrO2 content) 65,600 49,600 43,000 27,400 22

122

ZIRCONIUM AND HAFNIUM (Data in metric tons, unless otherwise noted)  

E-print Network

other companies. Zirconia (ZrO2) was produced from zircon sand at plants in Alabama, New Hampshire, New (ZrO2 content)1 100,000 100,000 100,000 100,000 100,000 Imports: Zirconium, ores and concentrates (ZrO2 content) 40,600 58,200 37,500 42,400 40,000 Zirconium, alloys, waste and scrap (ZrO2 content) 929

123

Graded selective coatings based on zirconium and titanium oxynitride  

Microsoft Academic Search

The aim of this study was the development and characterization of transition metal oxynitride multilayers for optical applications. The reactive RF magnetron sputtering technique in rotation mode was used for stacking of zirconium oxynitride (ZrNO) and titanium oxynitride (TiNO) nanolayers. The depositions were carried out in a reactive Ar+N2+O2 atmosphere by sputtering titanium and zirconium targets. By means of different

A. Rizzo; M. A. Signore; L. Tapfer; E. Piscopiello; A. Cappello; E. Bemporad; M. Sebastiani

2009-01-01

124

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

125

Zirconium alkoxide interfaces for adhesion enhancement and electrocatalysis  

NASA Astrophysics Data System (ADS)

Tetra(tert-butoxy)zirconium was chemisorbed onto the native oxide layers of aluminum, iron, copper, and porous silicon, forming surface bound di- or tri-alkoxy zirconium species. Poly(ethylene- co-acrylic acid) was subsequently reacted with the surface forming chemically bound copolymer through carboxyzirconium linkages. Copolymer bound through the zirconium complex adhered to the metal oxide surfaces better than without the zirconium alkoxide intermediate, as determined by FTIR spectroscopy. Copper substrates were subjected to a variety of stability tests, including exposure to ambient conditions, base washing, and chronocoulometry. The copper-zirconium-copolymer ensemble was shown to be very stable in all of these tests. Indium tin oxide (ITO) powder was titrated to determine surface hydroxyl content per unit area. ITO-coated glass slides were reacted with tetra( tert-butoxy)zirconium, and subsequently with both carboxylic acid and phenol derivatives. Ferrocene-carboxyzirconium-coated ITO was characterized electrochemically, and the surface loading of ferrocene was found to be approximately one monolayer. Phenoxyzirconium-coated ITO was also characterized electrochemically and tested for electrocatalytic properties for the oxidation of several compounds in solution. Phenoxyzirconium-coated ITO was found to improve the oxidation kinetics for ferrocene and tetramethylphenylenediamine in acetonitrile.

Vanderkam, Susan Killian

126

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

127

Nitrate Translocation by Detopped Corn Seedlings 1  

PubMed Central

Five-day-old seedlings of corn (Ze? mays L.) grown without nitrate were decapitated and exposed to 0.5 mm KNO3 or 0.5 mm KCl in aerated solutions at 30 C. Uptake of nitrate, chloride, and potassium was determined by replacing solutions hourly and measuring their depletion. Translocation of these ions and of organic nitrogen was determined by hourly analysis of the vascular exudate. Nitrate reduction was estimated by the difference between nitrate uptake and nitrate recovered in the tissue and exudate. Nitrate uptake exhibited its usual pattern of apparent induction resulting in the development of an accelerated uptake phase. Chloride uptake remained fairly constant throughout the experimental period. Translocation of nitrate increased progressively for at least 7 hours whereas chloride translocation reached a maximum about the 3d hour and then declined to a lower rate than nitrate translocation. Nitrate uptake and translocation were restricted by anaerobiosis, by 20 and 40 C relative to 30 C, and by 0.05 mm 6-methylpurine, an RNA-synthesis inhibitor. Accumulation, reduction and translocation of nitrate had different sensitivities to all these factors. The effect of 0.05 mm 6-methylpurine was more detrimental to nitrate translocation and nitrate reduction than to nitrate uptake. Ambient nitrate, relative to chloride, enhanced the exudation volume and the translocation of organic nitrogen within 4 hours from initiation of the experiments. Translocation of nitrate and organic nitrogen decreased shortly after removal of external nitrate. The higher rates of organic nitrogen translocation which occurred during nitrate uptake indicates either (a) rapid translocation of amino acids synthesized from the entering nitrate, or (b) an accelerated rate of protein turnover and a resulting enhancement in translocation of endogenous amino acids. PMID:16659246

Ezeta, Fernando N.; Jackson, William A.

1975-01-01

128

Short-term effects of a high nitrate diet on nitrate metabolism in healthy individuals.  

PubMed

Dietary nitrate, through the enterosalivary nitrate-nitrite-NO pathway, can improve blood pressure and arterial stiffness. How long systemic nitrate and nitrite remain elevated following cessation of high nitrate intake is unknown. In 19 healthy men and women, the time for salivary and plasma nitrate and nitrite to return to baseline after 7 days increased nitrate intake from green leafy vegetables was determined. Salivary and plasma nitrate and nitrite was measured at baseline [D0], end of high nitrate diet [D7], day 9 [+2D], day 14 [+7D] and day 21 [+14D]. Urinary nitrite and nitrate was assessed at D7 and +14D. Increased dietary nitrate for 7 days resulted in a more than fourfold increase in saliva and plasma nitrate and nitrite (p < 0.001) measured at [D7]. At [+2D] plasma nitrite and nitrate had returned to baseline while saliva nitrate and nitrite were more than 1.5 times higher than at baseline levels. By [+7D] all metabolites had returned to baseline levels. The pattern of response was similar between men and women. Urinary nitrate and nitrate was sevenfold higher at D7 compared to +14D. These results suggest that daily ingestion of nitrate may be required to maintain the physiological changes associated with high nitrate intake. PMID:25774606

Bondonno, Catherine P; Liu, Alex H; Croft, Kevin D; Ward, Natalie C; Puddey, Ian B; Woodman, Richard J; Hodgson, Jonathan M

2015-01-01

129

Acetonyltriphenyl­phospho­nium 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. PMID:23424568

Diop, Tidiane; Diop, Libasse; Ku?eráková, Monika; Dušek, Michal

2013-01-01

130

[Infantile methemoglobinemia caused by nitrates].  

PubMed

The intake of water or food with high levels of nitrates produces methemoglobinemia in infants up to 3 months of age. The study reviews factors in the environment and in the host that account for the increased risk in this age group. In order to reduce the prevalence of this problem, health authorities should control nitrate concentrations in drinking water, create adequate water supply systems, implement educational programs aimed at informing parents about preventive measures, and call on physicians to report cases of methemoglobinemia. PMID:2525389

de Fernícola, N A

1989-01-01

131

A biological source of oceanic alkyl nitrates  

NASA Astrophysics Data System (ADS)

Alkyl nitrates are an important component of reactive nitrogen in the troposphere. The oceans are a source of alkyl nitrates to the atmosphere, however the source of alkyl nitrates in the oceans is unknown. It has been demonstrated that the reaction of alkyl peroxy radicals (ROO) with nitric oxide (NO) produces alkyl nitrates in the aqueous phase. We hypothesize that alkyl nitrates may be formed by organisms through the same reaction and therefore biological production could be a source of alkyl nitrates to the troposphere. This work focuses on the production of alkyl nitrates by the diatoms Chaetoceros muelleri and Thalassiosira weisfloggi. Using chemostats, we measure alkyl nitrates formed under nitrate limited conditions. We also use triggers and inhibitors of nitric oxide formation to determine if alkyl nitrate formation is affected by changes in NO production. To date, the rates of production of alkyl nitrates in our cultures, lead us to estimate a production rate on the order of femtomolar/day for C1-C3 alkyl nitrates by diatom species in the equatorial Pacific Ocean. This suggests that diatoms may contribute to the overall ocean source of alkyl nitrates; however, it is possible that other types of phytoplankton, such as cyanobacteria, that are more abundant in the open ocean, may contribute to a greater extent.

Dahl, E. E.; Lewis, C. B.; Velasco, F. L.; Escobar, C.; Kellogg, D.; Velcamp, M.

2013-12-01

132

Understanding the Irradiation Behavior of Zirconium Carbide  

SciTech Connect

Zirconium carbide (ZrC) is being considered for utilization in high-temperature gas-cooled reactor fuels in deep-burn TRISO fuel. Zirconium carbide possesses a cubic B1-type crystal structure with a high melting point, exceptional hardness, and good thermal and electrical conductivities. The use of ZrC as part of the TRISO fuel requires a thorough understanding of its irradiation response. However, the radiation effects on ZrC are still poorly understood. The majority of the existing research is focused on the radiation damage phenomena at higher temperatures (>450{degree}C) where many fundamental aspects of defect production and kinetics cannot be easily distinguished. Little is known about basic defect formation, clustering, and evolution of ZrC under irradiation, although some atomistic simulation and phenomenological studies have been performed. Such detailed information is needed to construct a model describing the microstructural evolution in fast-neutron irradiated materials that will be of great technological importance for the development of ZrC- based fuel. The goal of the proposed project is to gain fundamental understanding of the radiation-induced defect formation in zirconium carbide and irradiation response (ZrC) by using a combination of state-of-the-art experimental methods and atomistic modeling. This project will combine (1) in situ ion irradiation at a specialized facility at a national laboratory, (2) controlled temperature proton irradiation on bulk samples, and (3) atomistic modeling to gain a fundamental understanding of defect formation in ZrC. The proposed project will cover the irradiation temperatures from cryogenic temperature to as high as 800{degree}C, and dose ranges from 0.1 to 100 dpa. The examination of this wide range of temperatures and doses allows us to obtain an experimental data set that can be effectively used to exercise and benchmark the computer calculations of defect properties. Combining the examination of radiation-induced microstructures mapped spatially and temporally, microstructural evolution during post-irradiation annealing, and atomistic modeling of defect formation and transport energetics will provide new, critical understanding about property changes in ZrC. The behavior of materials under irradiation is determined by the balance between damage production, defect clustering, and lattice response. In order to predict those effects at high temperatures so targeted testing can be expanded and extrapolated beyond the known database, it is necessary to determine the defect energetics and mobilities as these control damage accumulation and annealing. In particular, low-temperature irradiations are invaluable for determining the regions of defect mobility. Computer simulation techniques are particularly useful for identifying basic defect properties, especially if closely coupled with a well-constructed and complete experimental database. The close coupling of calculation and experiment in this project will provide mutual benchmarking and allow us to glean a deeper understanding of the irradiation response of ZrC, which can then be applied to the prediction of its behavior in reactor conditions.

Motta, Arthur; Sridharan, Kumar; Morgan, Dane; Szlufarska, Izabela

2013-10-11

133

Evaluating zirconium-zirconium hydride interfacial strains by nano-beam electron diffraction  

NASA Astrophysics Data System (ADS)

Nano-beam electron diffraction has been used to quantify the elastic strain field associated with ?-hydride needles embedded in an ?-Zr matrix. It has been found that the volume misfit associated with precipitation results in elastic strains that are ˜4× greater in the matrix than the hydride. Electron energy loss spectroscopy was used to detect hydrogen enrichment at the matrix-hydride interface by a shift in the zirconium plasmon peak. This work highlights that ?-hydride is metastable and acts as a precursor to equilibrium ?-hydride and that compositional variations within the hydride can be detected using electron energy loss spectroscopy.

Barrow, A. T. W.; Korinek, A.; Daymond, M. R.

2013-01-01

134

21 CFR 700.16 - Use of aerosol cosmetic products containing zirconium.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 2010-04-01 false Use of aerosol cosmetic products containing zirconium...Cosmetic Products § 700.16 Use of aerosol cosmetic products containing zirconium...that are also drugs, as, for example, aerosol antiperspirants. Evidence...

2010-04-01

135

21 CFR 172.170 - Sodium nitrate.  

Code of Federal Regulations, 2013 CFR

...FOOD FOR HUMAN CONSUMPTION (CONTINUED) FOOD ADDITIVES PERMITTED FOR DIRECT ADDITION TO FOOD FOR HUMAN CONSUMPTION Food Preservatives § 172.170 Sodium nitrate. The food additive sodium nitrate may be safely used in or...

2013-04-01

136

21 CFR 172.170 - Sodium nitrate.  

Code of Federal Regulations, 2012 CFR

...FOOD FOR HUMAN CONSUMPTION (CONTINUED) FOOD ADDITIVES PERMITTED FOR DIRECT ADDITION TO FOOD FOR HUMAN CONSUMPTION Food Preservatives § 172.170 Sodium nitrate. The food additive sodium nitrate may be safely used in or...

2012-04-01

137

21 CFR 172.170 - Sodium nitrate.  

Code of Federal Regulations, 2011 CFR

...FOOD FOR HUMAN CONSUMPTION (CONTINUED) FOOD ADDITIVES PERMITTED FOR DIRECT ADDITION TO FOOD FOR HUMAN CONSUMPTION Food Preservatives § 172.170 Sodium nitrate. The food additive sodium nitrate may be safely used in or...

2011-04-01

138

21 CFR 172.170 - Sodium nitrate.  

Code of Federal Regulations, 2010 CFR

...FOOD FOR HUMAN CONSUMPTION (CONTINUED) FOOD ADDITIVES PERMITTED FOR DIRECT ADDITION TO FOOD FOR HUMAN CONSUMPTION Food Preservatives § 172.170 Sodium nitrate. The food additive sodium nitrate may be safely used in or...

2010-04-01

139

21 CFR 172.170 - Sodium nitrate.  

Code of Federal Regulations, 2014 CFR

...HEALTH AND HUMAN SERVICES (CONTINUED) FOOD ADDITIVES PERMITTED FOR DIRECT ADDITION TO FOOD FOR HUMAN CONSUMPTION Food Preservatives § 172.170 Sodium nitrate. The food additive sodium nitrate may be safely used in or...

2014-04-01

140

Morphologies and growth mechanisms of zirconium carbide films by chemical vapor deposition  

Microsoft Academic Search

Zirconium carbide films were grown on graphite slices by chemical vapor deposition using methane, zirconium tetrachloride,\\u000a and hydrogen as precursors. The growth rate of zirconium carbide films as a function of temperature was investigated. The\\u000a morphologies of these films at different temperatures were also observed by scanning electron microscopy. The results indicated\\u000a that the deposition of zirconium carbide was dominated

Qiaomu Liu; Litong Zhang; Laifei Cheng; Yiguang Wang

2009-01-01

141

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

142

Deliquescence, Efflorescence, and Water Activity in Ammonium Nitrate and Mixed Ammonium Nitrate/Succinic Acid Microparticles  

E-print Network

not take up a significant amount of water. Additionally, the deliquescence relative humidity is foundDeliquescence, Efflorescence, and Water Activity in Ammonium Nitrate and Mixed Ammonium Nitrate of ammonium nitrate/water and mixed ammonium nitrate/succinic acid/water microparticles. The water activity

143

Constructed Marshes for Nitrate Removal  

Microsoft Academic Search

Large numbers of free water surface treatment wetlands are in use for nitrate reduction. Target applications are field runoff, river and stream improvement, and enhancement of wastewater treatment plants. In total, an extensive database now exists, in many publications and operating reports. Microcosms and mesocosms are not included here because of the lack of transferability to design. A first-order areal

Robert H. Kadlec

2012-01-01

144

Constructed Marshes for Nitrate Removal  

Microsoft Academic Search

Large numbers of free water surface treatment wetlands are in use for nitrate reduction. Target applications are field runoff, river and stream improvement, and enhancement of wastewater treatment plants. In total, an extensive database now exists, in many publications and operating reports. Microcosms and mesocosms are not included here, because of lack of transferability to design. A first-order areal model

Robert H. Kadlec

2011-01-01

145

Elimination of phosphate and zirconium in the high-activity fraction resulting from TRUEX partitioning of ICPP zirconium calcines  

SciTech Connect

Laboratory testing was undertaken with the aim of developing a TRUEX flowsheet that would efficiently remove actinides from solutions of dissolved zirconium calcine and minimize the glass volume produced from the ensuing high-activity fraction. A TRUEX flowsheet is recommended for testing in the 2-cm centrifugal contactor pilot-plant based on the results from this testing. These laboratory tests show that zirconium recovery in the high activity fraction is minimized by scrubbing with an optimized NHF concentration of 0.2 M. This NH4F concentration in the scrub allowed the HEDPA strip concentration to be reduced from 0.04 M to 0.004 M because HEDPA is not consumed by zirconium. Complete TRU stripping was also achieved in these laboratory tests with 0.004 M HEDPA. Data from the small-scale laboratory batch contact tests were used in the Generic TRUEX Model (GTM) to evaluate the proposed flowsheet under counter-current conditions. GTM results indicate the raffinate will meet the Class A non-TRU limit of < 10 nCi/g in six extraction stages (O/A = 1), and quantitative actinide recovery will be achieved with the 0.004 M HEDPA in six strip stages (O/A = 1). Only 6.6 % of the initial zirconium concentration is anticipated to be recovered with the actinides, indicating the four scrub stages (O/A = 3) efficiently removes zirconium from the TRUEX solvent. In addition to recommending an improved TRUEX flowsheet for testing in the 2-cm centrifugal contactor pilot-plant, this work has shown that small reductions in zirconium extraction drastically improves flowsheet performance. These small changes in zirconium extraction can be accomplished by modifying the calcine dissolution parameters. Therefore, further calcine dissolution testing followed by TRUEX testing with the resulting feed solutions is also recommended.

Brewer, K.N.; Tillotson, R.D.; Tullock, P.A. [and others

1997-07-01

146

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

147

Efflux Of Nitrate From Hydroponically Grown Wheat  

NASA Technical Reports Server (NTRS)

Report describes experiments to measure influx, and efflux of nitrate from hydroponically grown wheat seedlings. Ratio between efflux and influx greater in darkness than in light; increased with concentration of nitrate in nutrient solution. On basis of experiments, authors suggest nutrient solution optimized at lowest possible concentration of nitrate.

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

1992-01-01

148

Spatial Inference of Nitrate Concentrations in Groundwater  

E-print Network

of the fine-scale estimated nitrate concentration is obtained, as well as maps of the estimated county-level average nitrate concentration and similar maps at the level of watersheds and other geographic regions levels in drinking water. Nitrate occurs naturally in groundwater, but elevated levels can be caused

West, Mike

149

3, 59195976, 2003 The nitrate aerosol  

E-print Network

was used for model evalu- ation. During winter, fall and especially spring high nitrate levels aerosols. Also, inclusion of sea salt is necessary to properly assess the nitrate and nitric acid levelsACPD 3, 5919­5976, 2003 The nitrate aerosol field over Europe M. Schaap et al. Title Page Abstract

Paris-Sud XI, Université de

150

Modeling nitrate removal in a denitrification bed  

Technology Transfer Automated Retrieval System (TEKTRAN)

Denitrification beds are being promoted to reduce nitrate concentrations in agricultural drainage water to alleviate the adverse environmental effects associated with nitrate pollution in surface water. In this system, water flows through a trench filled with a carbon media where nitrate is transfor...

151

Nitrate removal from drinking water -- Review  

Microsoft Academic Search

Nitrate concentrations in surface water and especially in ground water have increased in Canada, the US, Europe, and other areas of the world. This trend has raised concern because nitrates cause methemoglobiinemia in infants. Several treatment processes including ion exchange, biological denitrification, chemical denitrification, reverse osmosis, electrodialysis, and catalytic denitrification can remove nitrates from water with varying degrees of efficiency,

Anoop Kapoor; T. Viraraghavan

1997-01-01

152

Three nitrate reductase activities in Alcaligenes eutrophus  

Microsoft Academic Search

Three nitrate reductase activities were detected in Alcaligenes eutrophus strain H16 by physiological and mutant analysis. The first (NAS) was subject to repression by ammonia and not affected by oxygen indicating a nitrate assimilatory function. The second (NAR) membrane-bound activity was only formed in the absence of oxygen and was insensitive to ammonia repression indicating a nitrate respiratory function. The

Ute Warnecke-Eberz; Bärbel Friedrich

1993-01-01

153

SOME PHYSICAL PROPERTIES OF URANYL NITRATE SOLUTIONS  

Microsoft Academic Search

Boillng points, freezing points, and densities were measured in the ;\\u000a concentration range between uranyl nitrate hexahydrate and uranyl nitrate ;\\u000a dihydrate. The surface tension of molten uranyl nitrate hexahydrate was ;\\u000a determined to be approximately 45 dynes per square centimeter at 90 to 1OO icient ;\\u000a laborato C. (auth)

G. P. Lang; M. O. Nethaway

1958-01-01

154

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

155

Chemical vapour deposition of zirconium carbide and silicon carbide hybrid whiskers  

Microsoft Academic Search

Zirconium carbide and silicon carbide hybrid whiskers were codeposited by chemical vapour deposition using methyl trichlorosilane, zirconium chloride, methane and hydrogen as the precursors. The zirconium carbide and silicon carbide whiskers were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction. The results indicate that the codeposition process is more effective in the presence of methane than

Qiaomu Liu; Litong Zhang; Laifei Cheng; Yiguang Wang

2010-01-01

156

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

NASA Astrophysics Data System (ADS)

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 rate saturated to 1.35 Å/cycle above 500 sccm of the argon purge flow rate. The growth rate, composition ratio ((Zr/Zr+Si)), and impurity contents (carbon and chlorine) saturated with the increase of the injection time of ZrCl4 and TBOS and decreased with the increased deposition temperature from 300 to 500 °C. The growth rate, composition ratio, carbon, and chlorine contents of the Zr silicate thin films deposited at 500 °C were 1.05 Å/cycle, 0.23, 1.1 at. %, and 2.1 at. %, respectively. It appeared that by using only zirconium chloride and silicon alkoxide sources, the content of carbon and chlorine impurities could not be lowered below 1%. It was also found that the incorporation rate of metal from halide source was lower than alkoxide source.

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

2002-11-01

157

Inhibition of Ice Growth and Recrystallization by Zirconium Acetate and Zirconium Acetate Hydroxide  

PubMed Central

The control over ice crystal growth, melting, and shaping is important in a variety of fields, including cell and food preservation and ice templating for the production of composite materials. Control over ice growth remains a challenge in industry, and the demand for new cryoprotectants is high. Naturally occurring cryoprotectants, such as antifreeze proteins (AFPs), present one solution for modulating ice crystal growth; however, the production of AFPs is expensive and inefficient. These obstacles can be overcome by identifying synthetic substitutes with similar AFP properties. Zirconium acetate (ZRA) was recently found to induce the formation of hexagonal cavities in materials prepared by ice templating. Here, we continue this line of study and examine the effects of ZRA and a related compound, zirconium acetate hydroxide (ZRAH), on ice growth, shaping, and recrystallization. We found that the growth rate of ice crystals was significantly reduced in the presence of ZRA and ZRAH, and that solutions containing these compounds display a small degree of thermal hysteresis, depending on the solution pH. The compounds were found to inhibit recrystallization in a manner similar to that observed in the presence of AFPs. The favorable properties of ZRA and ZRAH suggest tremendous potential utility in industrial applications. PMID:23555701

Mizrahy, Ortal; Bar-Dolev, Maya; Guy, Shlomit; Braslavsky, Ido

2013-01-01

158

Protection against oral and gastrointestinal diseases: importance of dietary nitrate intake, oral nitrate reduction and enterosalivary nitrate circulation.  

PubMed

Over the last 20 years, dietary nitrate has been implicated in the formation of methemoglobin and carcinogenic nitrosamines in humans. This has led to restrictions of nitrate and nitrite levels in food and drinking water. However, there is no epidemiological evidence for an increased risk of gastric and intestinal cancer in population groups with high dietary vegetable or nitrate intake. A reevaluation of our currently very negative perception of dietary nitrates comes from recent research into the metabolism and enterosalivary circulation of nitrate in mammals. These studies showed that nitrate is converted to nitrite in the oral cavity that then "fuels" an important mammalian resistance mechanism against infectious diseases. Moreover, there is now evidence that the conversion of nitrate into oxides of nitrogen prevents the formation carcinogenic nitrosamines. PMID:9505412

Duncan, C; Li, H; Dykhuizen, R; Frazer, R; Johnston, P; MacKnight, G; Smith, L; Lamza, K; McKenzie, H; Batt, L; Kelly, D; Golden, M; Benjamin, N; Leifert, C

1997-12-01

159

Continuous flow nitration in miniaturized devices  

PubMed Central

Summary This review highlights the state of the art in the field of continuous flow nitration with miniaturized devices. Although nitration has been one of the oldest and most important unit reactions, the advent of miniaturized devices has paved the way for new opportunities to reconsider the conventional approach for exothermic and selectivity sensitive nitration reactions. Four different approaches to flow nitration with microreactors are presented herein and discussed in view of their advantages, limitations and applicability of the information towards scale-up. Selected recent patents that disclose scale-up methodologies for continuous flow nitration are also briefly reviewed. PMID:24605161

2014-01-01

160

Continuous flow nitration in miniaturized devices.  

PubMed

This review highlights the state of the art in the field of continuous flow nitration with miniaturized devices. Although nitration has been one of the oldest and most important unit reactions, the advent of miniaturized devices has paved the way for new opportunities to reconsider the conventional approach for exothermic and selectivity sensitive nitration reactions. Four different approaches to flow nitration with microreactors are presented herein and discussed in view of their advantages, limitations and applicability of the information towards scale-up. Selected recent patents that disclose scale-up methodologies for continuous flow nitration are also briefly reviewed. PMID:24605161

Kulkarni, Amol A

2014-01-01

161

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. PMID:23200809

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

2012-01-01

162

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

163

Zirconium determination by cooling curve analysis during the pyroprocessing of used nuclear fuel  

NASA Astrophysics Data System (ADS)

An alternative method to sampling and chemical analyses has been developed to monitor the concentration of zirconium in real-time during the casting of uranium products from the pyroprocessing of used nuclear fuel. The method utilizes the solidification characteristics of the uranium products to determine zirconium levels based on standard cooling curve analyses and established binary phase diagram data. Numerous uranium products have been analyzed for their zirconium content and compared against measured zirconium data. From this data, the following equation was derived for the zirconium content of uranium products:

Westphal, B. R.; Price, J. C.; Bateman, K. J.; Marsden, K. C.

2015-02-01

164

A simple way to prepare precursors for zirconium carbide  

Microsoft Academic Search

A precursor for zirconium carbide was obtained by just blending zirconium butoxide Zr(OC4H9)4 (ZTB) and divinylbenzene (DVB). This precursor satisfied the requirements for use in ceramic matrix composites fabrication\\u000a via precursor infiltration and pyrolysis (PIP) process, that is, it was a solution, cross-linked at 150 °C for 2 h, and transformed\\u000a to ZrC matrix upon heat treatment at 1,600 °C with a ceramic

Dan Zhao; Haifeng Hu; Changrui Zhang; Yudi Zhang; Jun Wang

2010-01-01

165

First Order Pyramidal Slip of Screw Dislocations in Zirconium  

NASA Astrophysics Data System (ADS)

Atomistic simulations, based either on an empirical interatomic potential or on ab initio calculations, are used to study the pyramidal glide of a 1/3 <1-210> screw dislocation in hexagonal close-packed zirconium. Generalized stacking fault calculations reveal a metastable stacking fault in the first order pyramidal {10-11} plane, which corresponds to an elementary pyramidal twin. This fault is at the origin of a metastable configuration of the screw dislocation in zirconium, which spontaneously appears when the dislocation glides in the pyramidal plane.

Chaari, Nermine; Clouet, Emmanuel; Rodney, David

2014-12-01

166

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

167

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

168

EXAFS Studies of Amorphous Nickel-Zirconium Alloys  

NASA Astrophysics Data System (ADS)

Extended X-ray absorption fine structure (EXAFS) measurements have been made on the zirconium K absorption edge in amorphous NixZr1-x alloys with x{=}0.33, 0.50 and 0.67. The aim of this study is to understand the local structure vs composition in this system. It has been revealed as follows: (a) the bond length are 2.57 Å for the Zr-Ni pair and remain constant over the whole concentration range; (b) the second peak of the radial structure function consists of two component atoms, zirconium atom and nickel atom.

Maeda, Hironobu; Fukunaga, Toshiharu; Suzuki, Kenji; Osamura, Kouzo; Hida, Moritaka; Terauchi, Hikaru; Kamijo, Nagao

1988-06-01

169

Hydrogen pickup mechanism of zirconium alloys  

NASA Astrophysics Data System (ADS)

Although the optimization of zirconium based alloys has led to significant improvements in hydrogen pickup and corrosion resistance, the mechanisms by which such alloy improvements occur are still not well understood. In an effort to understand such mechanisms, a systematic study of the alloy effect on hydrogen pickup is conducted, using advanced characterization techniques to rationalize precise measurements of hydrogen pickup. The hydrogen pick-up fraction is accurately measured for a specially designed set of commercial and model alloys to investigate the effects of alloying elements, microstructure and corrosion kinetics on hydrogen uptake. Two different techniques to measure hydrogen concentrations were used: a destructive technique, Vacuum Hot Extraction, and a non-destructive one, Cold Neutron Prompt Gamma Activation Analysis. The results indicate that hydrogen pickup varies not only from alloy to alloy but also during the corrosion process for a given alloy. For instance Zircaloy type alloys show high hydrogen pickup fraction and sub-parabolic oxidation kinetics whereas ZrNb alloys show lower hydrogen pickup fraction and close to parabolic oxidation kinetics. Hypothesis is made that hydrogen pickup result from the need to balance charge during the corrosion reaction, such that the pickup of hydrogen is directly related to (and indivisible of) the corrosion mechanism and decreases when the rate of electron transport or oxide electronic conductivity sigmao xe through the protective oxide increases. According to this hypothesis, alloying elements (either in solid solution or in precipitates) embedded in the oxide as well as space charge variations in the oxide would impact the hydrogen pick-up fraction by modifying sigmaox e, which drives oxidation and hydriding kinetics. Dedicated experiments and modelling were performed to assess and validate these hypotheses. In-situ electrochemical impedance spectroscopy (EIS) experiments were performed on Zircaloy-4 tubes to directly measure the evolution of sigma oxe as function of exposure time. The results show that sigmao xe decreases as function of exposure time and that its variations are directly correlated to the instantaneous hydrogen pickup fraction variations. The electron transport through the oxide layer is thus altered as the oxide grows, reasons for which are yet to be exactly determined. Preliminary results also show that sigma oxe of ZrNb alloys would be much higher compared with Zircaloy-4. Thus, it is confirmed that sigmaox e is a key parameter in the hydrogen and oxidation mechanism. Because the mechanism whereby alloying elements are incorporated into the oxide layer is critical to changing sigmao xe, the evolution of the oxidation state of two common alloying elements, Fe and Nb, when incorporated into the growing oxide layers is investigated using X-Ray Absorption Near-Edge Spectroscopy (XANES) using micro-beam synchrotron radiation on cross sectional oxide samples. The results show that the oxidation of both Fe and Nb is delayed in the oxide layer compared to that of Zr, and that this oxidation delay is related to the variations of the instantaneous hydrogen pick-up fraction with exposure time. The evolution of Nb oxidation as function of oxide depth is also compatible with space charge compensation in the oxide and with an increase in sigmaox e of ZrNb alloys compared to Zircaloys. Finally, various successively complex models from the well-known Wagner oxidation theory to the more complex effect of space charge on oxidation kinetics have been developed. The general purpose of the modeling effort is to provide a rationale for the sub-parabolic oxidation kinetics and demonstrate the correlation with hydrogen pickup fraction. It is directly demonstrated that parabolic oxidation kinetics is associated with high sigmao xe and low space charges in the oxide whereas sub-parabolic oxidation kinetics is associated with lower sigmaox e and higher space charge in the oxide. All these observations helped us to propose a general corrosion mechanism of zirconium allo

Couet, Adrien

170

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

171

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

172

Characterization of uranium and uranium-zirconium deposits produced in electrorefining of spent nuclear fuel  

SciTech Connect

This paper describes the metallurgical characterization of deposits produced in molten salt electrorefining of uranium and uranium - 10.% zirconium alloy. The techniques of characterization are described with emphasis on considerations given to the radioactive and pyrophoric nature of the samples. The morphologies observed and their implications for deposit performance are also presented - samples from pure uranium deposits were comprised of chains of uranium crystals with a characteristic rhomboidal shape, while morphologies of samples from deposits containing zirconium showed more polycrystalline features. Zirconium was found to be present as a second, zirconium metal phase at or very near the uranium-zirconium dendrite surfaces. Higher collection efficiencies and total deposit weights were observed for the uranium-zirconium deposits; this performance increase is likely a result of better mechanical properties exhibited by the uranium-zirconium dendrite morphology. 18 refs., 10 figs., 1 tab.

Totemeier, T.C.

1997-09-01

173

Zirconium nanoparticles prepared by the reduction of zirconium oxide using the RAPET method  

PubMed Central

Summary The aim of the current work is the synthesis and characterization of metallic Zr nanoparticles. The preparation is carried out by using the RAPET method (Reaction under Autogenic Pressure at Elevated Temperatures) developed in our lab. The RAPET reaction of commercial ZrO2 with Mg powder was carried out in a closed stainless steel cell, at 750 °C. On completion of the reaction, the additionally formed MgO is removed by treatment with acid. The characterization of the product was performed by XRD, X-ray absorption spectroscopy, SEM, TEM and elemental analysis. The XRD pattern reveals that the product is composed of pure metallic zirconium, without any traces of the MgO by-product. PMID:21977431

Eshed, Michal; Pol, Swati; Balasubramanian, Mahalingam

2011-01-01

174

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

175

Fast photolysis of carbonyl nitrates from isoprene  

NASA Astrophysics Data System (ADS)

We show that photolysis is, by far, the major atmospheric sink of isoprene-derived carbonyl nitrates. Empirical evidence from published laboratory studies on the absorption cross sections and photolysis rates of ?-nitrooxy ketones suggests that the presence of the nitrate group (i) greatly enhances the absorption cross sections, and (ii) facilitates dissociation to a point that the photolysis quantum yield is close to unity, with O-NO2 dissociation as the likely major channel. On this basis, we provide new recommendations for estimating the cross sections and photolysis rates of carbonyl nitrates. The newly estimated photorates are validated using a chemical box model against measured temporal profiles of carbonyl nitrates in an isoprene oxidation experiment by Paulot et al. (2009). The comparisons for ethanal nitrate and for the sum of methacrolein- and methylvinylketone nitrates strongly supports our assumptions of large cross section enhancements and a near-unit quantum yield for these compounds. These findings have significant atmospheric implications, as carbonyl nitrates constitute an important component of the total organic nitrate pool over vegetated areas: the photorates of key carbonyl nitrates from isoprene are estimated to be typically between ~3 and 20 times higher than their sink due to reaction with OH in relevant atmospheric conditions. Moreover, since the reaction is expected to release NO2, photolysis is especially effective in depleting the total organic nitrate pool.

Müller, Jean-Francois; Peeters, Jozef; Stavrakou, Trisevgeni

2014-05-01

176

Nitrate deposition and impact of Adirondack streams  

SciTech Connect

Acidic deposition has a great impact on water chemistry and fish populations in the Adirondack region. Although the Clean Air Act Amendments of 1990 have resulted in some reductions of sulfur deposition, nitrate deposition has not yet been well controlled, and continues to impact aquatic resources. As part of the USEPA funded Episodic Response Project, four Adirondack headwater streams were intensively monitored over an 18 month period. Atmospheric deposition was also monitored at a centrally located station. The quantity of nitrate being deposited on the study watersheds was calculated based on monthly net deposition data, which ranged from 0.6 kg/ha/month to 3.6 kg/ha/month. These data were then compared to the monthly export of nitrate from the watershed in these streams. Nitrate concentrations were highest in the stream water during the spring snowmelt period prior to the time when forest vegetation actively utilizes nitrate. On an annual basis, the amount of nitrate that left the watershed via stream water was approximately equal to the amount that fell as nitrate deposition. These data are important in documenting the impact that nitrate has in acidifying Adirondack streams during the spring, which coincides with brook trout hatching. Control programs for nitrous oxide emissions are presently aimed at reducing ozone levels during the May--September period. These emissions control programs need to be expanded to also reduce nitrate deposition in the sensitive Adirondack region during the water and spring periods when nitrate deposition has its greatest impact on aquatic resources.

Simonin, H.A. [New York State Dept. of Environmental Conservation, Rome, NY (United States). Rome Field Station; Kretser, W. [New York State Dept. of Environmental Conservation, Ray Brook, NY (United States). Adirondack Lakes Survey Corp.

1995-12-31

177

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)

1987-01-01

178

Synthesis and Liquid Crystal Phase Transitions of Zirconium Phosphate Disks  

E-print Network

-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...

Shuai, Min

2013-05-07

179

Solid State Phase Transformations in Uranium-Zirconium Alloys  

E-print Network

, a basic study on the U-Zr metallurgy was completed using EPMA, DSC, XRD, Optical microscopy, and TEM with a focus on solid state phase transformations in alloys containing 2, 5, 10, 20, 30, and 50wt% zirconium. Alloys were cast by crucible melting...

Irukuvarghula, Sandeep

2013-08-06

180

Nanophase Nickel-Zirconium Alloys for Fuel Cells  

NASA Technical Reports Server (NTRS)

Nanophase nickel-zirconium alloys have been investigated for use as electrically conductive coatings and catalyst supports in fuel cells. Heretofore, noble metals have been used because they resist corrosion in the harsh, acidic fuel cell interior environments. However, the high cost of noble metals has prompted a search for less-costly substitutes. Nickel-zirconium alloys belong to a class of base metal alloys formed from transition elements of widely different d-electron configurations. These alloys generally exhibit unique physical, chemical, and metallurgical properties that can include corrosion resistance. Inasmuch as corrosion is accelerated by free-energy differences between bulk material and grain boundaries, it was conjectured that amorphous (glassy) and nanophase forms of these alloys could offer the desired corrosion resistance. For experiments to test the conjecture, thin alloy films containing various proportions of nickel and zirconium were deposited by magnetron and radiofrequency co-sputtering of nickel and zirconium. The results of x-ray diffraction studies of the deposited films suggested that the films had a nanophase and nearly amorphous character.

Narayanan, Sekharipuram; Whitacre, jay; Valdez, Thomas

2008-01-01

181

Discovery of Yttrium, Zirconium, Niobium, Technetium, and Ruthenium Isotopes  

E-print Network

Currently, thirty-four yttrium, thirty-five zirconium, thirty-four niobium, thirty-five technetium, and thirty-eight ruthenium isotopes have been observed and the discovery of these isotopes is discussed here. For each isotope a brief synopsis of the first refereed publication, including the production and identification method, is presented.

Nystrom, A

2011-01-01

182

Discovery of Yttrium, Zirconium, Niobium, Technetium, and Ruthenium Isotopes  

E-print Network

Currently, thirty-four yttrium, thirty-five zirconium, thirty-four niobium, thirty-five technetium, and thirty-eight ruthenium isotopes have been observed and the discovery of these isotopes is discussed here. For each isotope a brief synopsis of the first refereed publication, including the production and identification method, is presented.

A. Nystrom; M. Thoennessen

2011-02-11

183

Phosphorus Recovery Using Zirconium-Loaded Saponified Orange Juice Residue  

NASA Astrophysics Data System (ADS)

Zirconium was immobilized to orange juice residue, to investigate the feasibility of using zirconium-loaded saponified orange juice residue (Zr-SOJR) for phosphorus recovery from secondary effluent and the extraction solution from incinerated sewage sludge ash by using H2SO4 and HCl. These had phosphorus concentrations of 68.2 mg/dm3 and 5.9 mg/dm3, respectively. The phosphorus removal rate secondary effluent increased with an increasing solid/liquid ratio in batch experiments. The adsorption capacity of Zr-SOJR was also compared with those obtained using a synthetic phosphorus solution and using zirconium-loaded ferrite. The prepared absorbent was effective for phosphorus removal and exhibited a reasonably high sorption capacity, twice that of zirconium ferrite. Secondary effluent was treated by packed column, and this reached break-through after 300 bed volumes. The results from phosphorous extraction from the ash indicate that can be treated with acid to efficiently recover phosphorous and thus can be absorbed by Zr-SOJR.

Harada, Hiroyuki; Kondo, Mitsunori; Biswas, Biplob K.; Ohura, Seichirou; Inoue, Katsutoshi; Ishikawa, Susumu; Kawakita, Hidetaka; Ohto, Keisuke

184

Hydrogen pickup measurements in zirconium alloys: Relation to oxidation kinetics  

E-print Network

Hydrogen pickup measurements in zirconium alloys: Relation to oxidation kinetics Adrien Couet a 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

Motta, Arthur T.

185

Pollution of drinking water with nitrate  

Microsoft Academic Search

The main sources of nitrate in man are food and drinking water. The legislature in West Germany intends to lower the permitted level of nitrate in drinking water from the present 90 mg\\/l to 50 mg\\/l in 1982. The European Community has issued a directive that recommends a level of only 25 mg\\/l, and for babies 10 mg\\/l nitrate should

B. Cabel; R. Kozicki; U. Lahl; A. Podbielshi; B. Stachel; S. Struss

1982-01-01

186

Safety in the Chemical Laboratory: Nitric Acid, Nitrates, and Nitro Compounds.  

ERIC Educational Resources Information Center

Discussed are the potential hazards associated with nitric acid, inorganic and organic nitrate salts, alkyl nitrates, acyl nitrates, aliphatic nitro compounds, aromatic nitro compounds, and nitration reactions. (CW)

Bretherick, Leslie

1989-01-01

187

49 CFR 176.410 - Division 1.5 materials, ammonium nitrate and ammonium nitrate mixtures.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 false Division 1.5 materials, ammonium nitrate and ammonium nitrate...Transportation PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION HAZARDOUS MATERIALS REGULATIONS CARRIAGE BY...

2010-10-01

188

49 CFR 176.410 - Division 1.5 materials, ammonium nitrate and ammonium nitrate mixtures.  

Code of Federal Regulations, 2011 CFR

...5 compatibility group D. (f) No mixture containing ammonium nitrate and any ingredient which would accelerate the decomposition of ammonium nitrate under conditions incident to transportation may be transported by vessel. [Amdt. 176-30,...

2011-10-01

189

49 CFR 176.410 - Division 1.5 materials, ammonium nitrate and ammonium nitrate mixtures.  

Code of Federal Regulations, 2014 CFR

...5 compatibility group D. (f) No mixture containing ammonium nitrate and any ingredient which would accelerate the decomposition of ammonium nitrate under conditions incident to transportation may be transported by vessel. [Amdt. 176-30,...

2014-10-01

190

49 CFR 176.410 - Division 1.5 materials, ammonium nitrate and ammonium nitrate mixtures.  

Code of Federal Regulations, 2012 CFR

...5 compatibility group D. (f) No mixture containing ammonium nitrate and any ingredient which would accelerate the decomposition of ammonium nitrate under conditions incident to transportation may be transported by vessel. [Amdt. 176-30,...

2012-10-01

191

49 CFR 176.410 - Division 1.5 materials, ammonium nitrate and ammonium nitrate mixtures.  

Code of Federal Regulations, 2013 CFR

...5 compatibility group D. (f) No mixture containing ammonium nitrate and any ingredient which would accelerate the decomposition of ammonium nitrate under conditions incident to transportation may be transported by vessel. [Amdt. 176-30,...

2013-10-01

192

Fast photolysis of carbonyl nitrates from isoprene  

NASA Astrophysics Data System (ADS)

Photolysis is shown to be a major sink for isoprene-derived carbonyl nitrates, which constitute an important component of the total organic nitrate pool over vegetated areas. Empirical evidence from published laboratory studies on the absorption cross sections and photolysis rates of ?-nitrooxy ketones suggests that the presence of the nitrate group (i) greatly enhances the absorption cross sections and (ii) facilitates dissociation to a point that the photolysis quantum yield is close to unity, with O-NO2 dissociation as a likely major channel. On this basis, we provide new recommendations for estimating the cross sections and photolysis rates of carbonyl nitrates. The newly estimated photo rates are validated using a chemical box model against measured temporal profiles of carbonyl nitrates in an isoprene oxidation experiment by Paulot et al. (2009). The comparisons for ethanal nitrate and for the sum of methacrolein- and methyl vinyl ketone nitrates strongly supports our assumptions of large cross-section enhancements and a near-unit quantum yield for these compounds. These findings have significant atmospheric implications: the photorates of key carbonyl nitrates from isoprene are estimated to be typically between ~ 3 and 20 times higher than their sink due to reaction with OH in relevant atmospheric conditions. Moreover, since the reaction is expected to release NO2, photolysis is especially effective in depleting the total organic nitrate pool.

Müller, J.-F.; Peeters, J.; Stavrakou, T.

2014-03-01

193

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

194

Free amino acids, nitrate, and nitrate reductase in nitrogen fixation by soybean nodules  

E-print Network

FREE AMINO ACIDS, NITRATE, AND NITRATE REDUCTASE IN NITROGEN FIXATION BY SOYBEAN NODULES A Thesis by PAUL CLAYTON MADTES, JR. Submitted to the Graduate College of Texas A&M University in partial fulfillment of the requirement for the degree... of MASTER OF SCIENCE December 1978 Major Subject: Biophysics FREE AMINO ACIDS, NITRATE, AND NITRATE REDUCTASE IN NITROGEN FIXATION BY SOYBEAN NPDULES A Thesis by PAUL CLAYTON MADTES, JR. Approved as to style and content by: g jap (Chairman...

Madtes, Paul Clayton

1978-01-01

195

Effect of nitrate and incubation conditions on the production of catalase and nitrate reductase by staphylococci  

Microsoft Academic Search

The objective of this work was to study the production of catalase and nitrate reductase by staphylococci in order to understand their role in lipid oxidation during sausage manufacturing. Catalase and nitrate reductase were measured in resting cells and supernatants of staphylococci grown in different conditions. All staphylococci (except S. warneri) synthetized nitrate reductase. In static condition, the synthesis was

R Talon; D Walter; S Chartier; C Barrière; M. C Montel

1999-01-01

196

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

197

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

198

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 ...

199

Nitration of Benzo Crown Ethers with Potassium Nitrate in Polyphosphoric Acid  

Microsoft Academic Search

A general method for the nitration of benzo crown ethers with potassium nitrate in polyphosphoric acid has been developed. Mono- and dinitro derivatives of benzo-12-crown-4, benzo-15-crown-5, dibenzo-18-crown-6, and dibenzo-24-crown-8 have been prepared. The role of complex formation in the regioselective tendency for the nitration of dibenzo-18-crown-6 has been demonstrated.

A. D. Grebenyuk; S. A. Andreev; I. A. Stempnevskaya; M. G. Levkovich; A. K. Tashmukhamedova

2000-01-01

200

The NreA protein functions as a nitrate receptor in the staphylococcal nitrate regulation system.  

PubMed

Staphylococci are able to use nitrate as an alternative electron acceptor during anaerobic respiration. The regulation of energy metabolism is dependent on the presence of oxygen and nitrate. Under anaerobic conditions, staphylococci employ the nitrate regulatory element (Nre) for transcriptional activation of genes involved in reduction and transport of nitrate and nitrite. Of the three proteins that constitute the Nre system, NreB has been characterized as an oxygen sensor kinase and NreC has been characterized as its cognate response regulator. Here, we present structural and functional data that establish NreA as a new type of nitrate receptor. The structure of NreA with bound nitrate was solved at 2.35Å resolution, revealing a GAF domain fold. Isothermal titration calorimetry experiments showed that NreA binds nitrate with low micromolar affinity (KD=22?M). Two crystal forms for NreA were obtained, with either bound nitrate or iodide. While the binding site is hydrophobic, two helix dipoles and polar interactions contribute to specific binding of the ions. The expression of nitrate reductase (NarGHI) was examined using a narG-lip (lipase) reporter gene assay in vivo. Expression was regulated by the presence of NreA and nitrate. Structure-guided mutations of NreA reduced its nitrate binding affinity and also affected the gene expression, thus providing support for the function of NreA as a nitrate receptor. PMID:24389349

Niemann, Volker; Koch-Singenstreu, Mareike; Neu, Ancilla; Nilkens, Stephanie; Götz, Friedrich; Unden, Gottfried; Stehle, Thilo

2014-04-01

201

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

202

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. PMID:24728381

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

2014-01-01

203

Nuclear-grade zirconium prepared by combining combustion synthesis with molten-salt electrorefining technique  

NASA Astrophysics Data System (ADS)

Zirconium has a low absorption cross-section for neutrons, which makes it an ideal material for use in nuclear reactor applications. However, hafnium typically contained in zirconium causes it to be far less useful for nuclear reactor materials because of its high neutron-absorbing properties. In the present study, a novel effective method has been developed for the production of hafnium-free zirconium. The process includes two main stages: magnesio-thermic reduction of ZrSiO 4 under a combustion mode, to produce zirconium silicide (ZrSi), and recovery of hafnium-free zirconium by molten-salt electrorefining. It was found that, depending on the electrorefining procedure, it is possible to produce zirconium powder with a low hafnium content: 70 ppm, determined by ICP-AES analysis.

Li, Hui; Nersisyan, Hayk H.; Park, Kyung-Tae; Park, Sung-Bin; Kim, Jeong-Guk; Lee, Jeong-Min; Lee, Jong-Hyeon

2011-06-01

204

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

205

78 FR 32690 - Certain Ammonium Nitrate From Ukraine  

Federal Register 2010, 2011, 2012, 2013, 2014

...Review)] Certain Ammonium Nitrate From Ukraine Determination On the basis of the record...order on certain ammonium nitrate from Ukraine would be likely to lead to continuation...entitled Certain Ammonium Nitrate from Ukraine: Investigation No....

2013-05-31

206

70. INTERIOR VIEW OF AMMONIUM NITRATE HOUSE, LOOKING AT AMMONIUM ...  

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

70. INTERIOR VIEW OF AMMONIUM NITRATE HOUSE, LOOKING AT AMMONIUM NITRATE IN STORAGE. APRIL 18, 1919. - United States Nitrate Plant No. 2, Reservation Road, Muscle Shoals, Muscle Shoals, Colbert County, AL

207

46 CFR 148.227 - Calcium nitrate fertilizers.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 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...

2012-10-01

208

46 CFR 148.227 - Calcium nitrate fertilizers.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 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...

2011-10-01

209

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

210

46 CFR 148.227 - Calcium nitrate fertilizers.  

Code of Federal Regulations, 2014 CFR

...2014-10-01 2014-10-01 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...

2014-10-01

211

Anaerobic benzene biodegradation linked to nitrate reduction  

SciTech Connect

Benzene oxidation to carbon dioxide linked to nitrate reduction was observed in enrichment cultures developed from soil and groundwater microcosms. Benzene biodegradation occurred concurrently with nitrate reduction at a constant ratio of 10 mol of nitrate consumed per mol of benzene degraded. Benzene biodegradation linked to nitrate reduction was associated with cell growth; however, the yield, 8.8 g (dry weight) of cells per mol of benzene, was less than 15% of the predicted yield for benzene biodegradation linked to nitrate reduction. In experiments performed with [{sup 14}C]benzene, approximately 92 to 95% of the label was recovered in {sup 14}CO{sub 2}, while the remaining 5 to 8% was incorporated into the nonvolatile fraction (presumably biomass), which is consistent with the low measured yield. In benzene-degrading cultures, nitrite accumulated stoichiometrically as nitrate was reduced and then was slowly reduced to nitrogen gas. When nitrate was depleted and only nitrite remained, the rate of benzene degradation decreased to almost zero. Based on electron balances, benzene biodegradation appears to be coupled more tightly to nitrate reduction to nitrite than to further reduction of nitrite to nitrogen gas.

Burland, S.M. [McMaster Univ., Hamilton, Ontario (Canada). Dept. of Civil Engineering; Edwards, E.A. [Univ. of Toronto, Ontario (Canada). Dept. of Chemical Engineering and Applied Chemistry

1999-02-01

212

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...

213

NITRATE CONTAMINATION OF GROUND WATER (GW-761)  

EPA Science Inventory

The occurrence of nitrate and related compounds in ground water is discussed from the perspectives of its natural as well as anthropogenic origins. A brief explanation of the nitrogen cycle touches on the production as well as utilization of ammonia, nitrite, nitrate, and nitrog...

214

THERMAL DECOMPOSITION OF URANYL NITRATE HEXAHYDRATE  

Microsoft Academic Search

The thermal decomposition of uranyl nitrate hexahydrate was studied in ; the temperature range of 250to 400 deg C at atmospheric and at <0.1 mm pressure. ; The intermediate and final products of the decomposition were determined. The ; decomposition follows a zero-order reaction until less than half of the uranyl ; nitrate remains. The remaining portion of the decomposition

Ondrejcin

1963-01-01

215

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...

216

Addressing Nitrate in California's Drinking Water  

E-print Network

Addressing Nitrate in California's Drinking Water Report for the State Water Resources Control #12;Addressing Nitrate in California's Drinking Water With a Focus on Tulare Lake Basin and Salinas status, age, sexual orientation, citizenship, or service in the uniformed services (as defined

Pasternack, Gregory B.

217

Nitrates and Prussic Acid in Forages  

E-print Network

When nitrates and prussic acid accumulate in forage, the feed may not be safe for livestock consumption. Learn the symptoms of nitrate and prussic acid poisoning and which plants are most likely to pose a risk to livestock. Also learn sampling...

Provin, Tony; Pitt, John L.

2003-01-06

218

The effect of zirconium on the cyclic oxidation of NiCrAl alloys  

NASA Technical Reports Server (NTRS)

This paper examines results with cyclic oxidation tests of Ni(9-20) Cr(15-30) Al-(x)Zr alloys carried out at 1100 C and 1200 C in static air. The concentration of zirconium varies from 0 to 0.63 atomic percent. Significant aluminum penetration is found in metallographic and electron microscopic examination of oxidized surfaces. Small amounts of zirconium lead to minimal penetration, and with increased zirconium content pronounced oxide penetration is observed.

Barrett, C. A.; Khan, A. S.; Lowell, C. E.

1981-01-01

219

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

220

Alternative Processing of High Temperature Hafnium and Zirconium Based Materials  

NASA Technical Reports Server (NTRS)

The behavior of refractory hafnium and zirconium based materials are being investigated at NASA Ames as part of ongoing research aimed at developing superior heat resistant materials for aerospace applications. Hafnium and zirconium diboride based materials have shown high temperature capabilities in simulated reentry environments indicating that these materials may successfully operate as reusable oxidation resistant components for leading edge applications. Due to the refractory nature of these materials, processing of fine-grained uniform microstructures poses a number of challenges. To better understand the process-property-microstructure relationship, processing of these materials has been carried out with conventional hot pressing in addition to the novel approach of Spark Plasma Sintering (SPS). The two processing methods are compared and contrasted in an evaluation of the sintering behavior of high temperature diboride based materials and preliminary physical and mechanical properties are presented.

Gasch, Matthew; Gusman, Michael; Ellerby, Don; Irby, Edward; Johnson, Sylvia M.

2003-01-01

221

Modelling zirconium hydrides using the special quasirandom structure approach.  

PubMed

The study of the structure and properties of zirconium hydrides is important for understanding the embrittlement of zirconium alloys used as cladding in light water nuclear reactors. Simulation of the defect processes is complicated due to the random distribution of the hydrogen atoms. We propose the use of the special quasirandom structure approach as a computationally efficient way to describe this random distribution. We have generated six special quasirandom structure cells based on face centered cubic and face centered tetragonal unit cells to describe ZrH(2-x) (x = 0.25-0.5). Using density functional theory calculations we investigate the mechanical properties, stability, and electronic structure of the alloys. PMID:23588997

Wang, H; Chroneos, A; Jiang, C; Schwingenschlögl, U

2013-05-28

222

Phase diagram of ammonium nitrate  

NASA Astrophysics Data System (ADS)

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.

Dunuwille, Mihindra; Yoo, Choong-Shik

2013-12-01

223

ZIRCONIUM AND HAFNIUM (Data in metric tons, unless noted)  

E-print Network

companies as well. Zirconia (ZrO2) was produced from zircon sand at plants in Alabama, New Hampshire, New in superalloys. Salient Statistics--United States: 1991 1992 1993 1994 1995e Production: Zircon (ZrO2 content)1 67,000 70,300 W W W Imports: Zirconium, ores and concentrates (ZrO2 content) 23,200 24,300 45,500 53

224

ZIRCONIUM AND HAFNIUM (Data in metric tons, unless otherwise noted)  

E-print Network

. Zirconia (ZrO2) was produced from zircon sand at plants in Alabama, New Hampshire, New York, Ohio in superalloys. Salient Statistics--United States: 1999 2000 2001 2002 2003e Production, zircon (ZrO2 content)1 100,000 100,000 100,000 100,000 100,000 Imports: Zirconium, ores and concentrates (ZrO2 content) 37

225

Cesium Adsorption on the ZIRCONIUM\\/OXYGEN\\/TUNGSTEN(100) Surface  

Microsoft Academic Search

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,

Hsiung-Ku. Chen

1983-01-01

226

Synthesis and characterization of titanium and zirconium oxynitride coatings  

Microsoft Academic Search

Thin films of zirconium oxynitride (ZrNO) and titanium oxynitride (TiNO) have been deposited onto Si(100) substrates at room temperature by radiofrequency magnetron sputtering in an argon–oxygen–nitrogen atmosphere. Single oxynitride layers have been stacked to obtain a multilayer structure. The film structure has been determined by X-ray diffraction while compositional analysis has been performed by X-photoelectrons spectroscopy. Structural analysis has shown

A. Rizzo; M. A. Signore; L. Mirenghi; T. Di Luccio

2009-01-01

227

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

228

Influence de la teneur en nitrate sur l'volution des activits nitrate rductase et nitrognase du  

E-print Network

: Assimilation du nitrate, fixation de l'azote, nodulation. SUMMARY Influence of nitrate levels on nitrate solutions providing 0, 1.5, 5 and 15 mM NO3. Nitrate reductase activity increased with increasing levelsInfluence de la teneur en nitrate sur l'évolution des activités nitrate réductase et nitrogénase du

Paris-Sud XI, Université de

229

Ferrier rearrangement promoted by an electrochemically generated zirconium catalyst.  

PubMed

In situ generated zirconium catalyst from a sacrificial zirconium anode was successfully applied to promote Ferrier rearrangement of 3,4,5-tri-O-acetyl-d-glucal and 6-deoxy-3,4-di-O-acetyl-l-glucal (3,4-di-O-acetyl-l-rhamnal) in the presence of three thiols and eleven thiophenols as nucleophiles. A simple constant current electrolysis (20 mA, 0.4 F mol(-1)) of an acetonitrile solution of lithium perchlorate (0.1 M) containing the corresponding glycal and S-nucleophiles, using a zirconium anode and a platinum cathode resulted in the successful synthesis of the corresponding 2,3-unsaturated peracetylated thioglycosides (with an average anomer ratio ?/?=4.129 in the case of peracetylated d-glucal and 8.740 in the case of l-rhamnal). The same procedure proved to be appropriate in synthesizing dihydropyran derivatives ('C-glycosides') using allyltrimethylsilane as the nucleophile (only '?-anomers' were obtained). All new compounds were fully characterized by spectral data, whereas single-crystal X-ray analysis was performed for two thioglycosides. PMID:25746956

Stevanovi?, Dragana; Pejovi?, Anka; Damljanovi?, Ivan; Mini?, Aleksandra; Bogdanovi?, Goran A; Vuki?evi?, Mirjana; Radulovi?, Niko S; Vuki?evi?, Rastko D

2015-04-30

230

Laves intermetallics in stainless steel-zirconium alloys  

SciTech Connect

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 diffraction measurements, heat-treatment studies and mechanical testing on SS-15Zr alloys. The Laves intermetallics in these alloys, labeled Zr(Fe,Cr,Ni){sub 2+x}, have both C36 and C15 crystal structures. A fraction of these intermetallics transform into (Fe,Cr,Ni){sub 23}Zr{sub 6} during high-temperature annealing; the authors have proposed a mechanism for this transformation. The SS-15Zr alloys show virtually no elongation in uniaxial tension, but exhibit good strength and ductility in compression tests. This article also presents neutron diffraction and microstructural data for a stainless steel-42 wt.% zirconium (SS-42Zr) alloy.

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

1997-05-01

231

Effects of high nitrate intake in rats.  

PubMed

The purpose of this study was to determine the effects of administration of high dose nitrate in drinking water on weight gain, hematological parameters and osmotic fragility in rats. We compared these parameters in 40 rats divided into four groups (one control and three treatment groups). Control animals drank filtered tap water containing a maximum of 10 mg/l nitrate while the treatment groups drank 100 mg/l, 200 mg/l and 400 mg/l nitrate-containing water ad libitum for 60 days. Animals in the treatment groups gained less weight than the control group and the differences between the control and treatment groups were statistically significant (p < 0.05). At the concentration of 100 mg/l nitrate, platelet counts and hemoglobin levels were significantly increased compared with the control group (p < 0.05). At the concentration of 200 mg/l nitrate, erythrocyte counts, hemoglobin and hematocrit levels were significantly increased compared with the control group (p < 0.05). At the concentration of 400 mg/l nitrate, platelet counts were decreased significantly when compared with the first two treatment groups (p < 0.05). There were statistically significant differences in osmotic fragility ratios between treatment groups and the control group (p < 0.05). We concluded that high nitrate intake in drinking water decreases weight gain, affects hematological parameters by inducing bone marrow activity at low doses and inhibiting it at high doses, and increases erythrocyte osmotic fragility. PMID:10851662

O?ur, R; Korkmaz, A; Hasde, M

2000-01-01

232

Modeling nitrate removal in a denitrification bed.  

PubMed

Denitrification beds are promoted to reduce nitrate load in agricultural subsurface drainage water to alleviate the adverse environmental effects associated with nitrate pollution of surface water. In this system, drainage water flows through a trench filled with a carbon media where nitrate is transformed into nitrogen gas under anaerobic conditions. The main objectives of this study were to model a denitrification bed treating drainage water and evaluate its adverse greenhouse gas emissions. Field experiments were conducted at an existing denitrification bed. Evaluations showed very low greenhouse gas emissions (mean N2O emission of 0.12 ?g N m(-2) min(-1)) from the denitrification bed surface. Field experiments indicated that nitrate removal rate was described by Michaelis-Menten kinetics with the Michaelis-Menten constant of 7.2 mg N L(-1). We developed a novel denitrification bed model based on the governing equations for water flow and nitrate removal kinetics. The model evaluation statistics showed satisfactory prediction of bed outflow nitrate concentration during subsurface drainage flow. The model can be used to design denitrification beds with efficient nitrate removal which in turn leads to enhanced drainage water quality. PMID:25638338

Ghane, Ehsan; Fausey, Norman R; Brown, Larry C

2015-03-15

233

Microbial Uranium Immobilization Independent of Nitrate Reduction  

SciTech Connect

At many uranium processing and handling facilities, including sites in the U.S. Department of Energy (DOE) complex, high levels of nitrate are present as co-contamination with uranium in groundwater. The daunting prospect of complete nitrate removal prior to the reduction of uranium provides a strong incentive to explore bioremediation strategies that allow for uranium bioreduction and stabilization in the presence of nitrate. Typical in-situ strategies involving the stimulation of metal-reducing bacteria are hindered by low pH environments at this study site and require that the persistent nitrate must first and continuously be removed or transformed prior to uranium being a preferred electron acceptor. This project investigates the possibility of stimulating nitrate-indifferent, pH-tolerant microorganisms to achieve bioreduction of U(VI) despite nitrate persistence. Successful enrichments from U-contaminated sediments demonstrated nearly complete reduction of uranium with very little loss of nitrate from pH 4.9-5.6 using methanol or glycerol as a carbon source. Higher pH enrichments also demonstrated similar U reduction capacity with 5-30% nitrate loss within one week. Bacterial 16S rRNA genes were amplified from uranium-reducing enrichments (pH 5.7-6.7) and sequenced. Phylogenetic analyses classified the clone sequences into four distinct clusters. Data from sequencing and T-RFLP profiles indicated that the majority of the microorganisms stimulated by these enrichment conditions consisted of low G+C Gram-positive bacteria most closely related to Clostridium and Clostridium-like organisms. This research demonstrates that the stimulation of a natural microbial community to immobilize U through bioreduction is possible without the removal of nitrate.

Madden, Andrew [ORNL; Smith, April [Florida State University; Balkwill, Dr. David [Florida State University; Fagan, Lisa Anne [ORNL; Phelps, Tommy Joe [ORNL

2007-01-01

234

77 FR 65532 - Solid Fertilizer Grade Ammonium Nitrate From the Russian Federation: Notice of Rescission of...  

Federal Register 2010, 2011, 2012, 2013, 2014

...Fertilizer Grade Ammonium Nitrate From the Russian Federation: Notice of Rescission of Antidumping...nitrate (ammonium nitrate) from the Russian Federation (Russia) for the period of...Nitrate (Ammonium Nitrate) from the Russian Federation (Russia): Data Query...

2012-10-29

235

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

236

Electrophilic and free radical nitration of benzene and toluene with various nitrating agents*  

PubMed Central

Electrophilic nitration of toluene and benzene was studied under various conditions with several nitrating systems. It was found that high orthopara regioselectivity is prevalent in all reactions and is independent of the reactivity of the nitrating agent. The methyl group of toluene is predominantly ortho-para directing under all reaction conditions. Steric factors are considered to be important but not the sole reason for the variation in the ortho/para ratio. The results reinforce our earlier views that, in electrophilic aromatic nitrations with reactive nitrating agents, substrate and positional selectivities are determined in two separate steps. The first step involves a ?-aromatic-NO2+ ion complex or encounter pair, whereas the subsequent step is of arenium ion nature (separate for the ortho, meta, and para positions). The former determines substrate selectivity, whereas the latter determines regioselectivity. Thermal free radical nitration of benzene and toluene with tetranitromethane in sharp contrast gave nearly statistical product distributions. PMID:16592503

Olah, George A.; Lin, Henry C.; Olah, Judith A.; Narang, Subhash C.

1978-01-01

237

Relationships between nitrate level, nitrate reductase activity and anaerobic nitrite production in Pisum sativum leaf tissue  

Microsoft Academic Search

Anaerobic nitrite production (thein vivo NO3-R activity) in an incubation medium lacking exogenous nitrate but containing 0.5%n-propanol and 0.1% Triton X-100 showed higher correlation (y - ax\\u000a b) with the level of endogenous nitrate inPisum sativum L. leaves than thein vitro nitrate reductase activity. Thein vivo NO3-R activity correlated well with thein vitro activity up to the 50 ppm NO3-N

V. Škrdleta; Alena Gaudinová; Marie N?mcová

1979-01-01

238

Sap Analysis for Diagnosis of Nitrate Accumulation in Cereal Forages  

E-print Network

on the concentration of nitrate in the forage and the level of consumption. Recommendations for mixing forage of nitrate levels in cured hay (Tables 1 and 2). We sought to develop a new quicktest for nitrate in cereal the lower nodes of selected small grain forages at the time of harvest are correlated with nitrate levels

Lawrence, Rick L.

239

Article original Teneur en nitrate du lait. Relation  

E-print Network

: relationship with nitrate level In livestock water sources. Environmental pollution leads to increasing nitrate levels in dairy cattle'swater supply. Possible re- percussions regarding nitrate content in milk shouldArticle original Teneur en nitrate du lait. Relation avec sa concentration dans l'eau d

Paris-Sud XI, Université de

240

Separation of Zirconium from Uranium in U-Zr Alloys Using a Chlorination Process  

E-print Network

........................................................... 12 2.2.1 Chloride Processing ................................................................................... 13 2.2.2 Fluoride Processing .................................................................................... 15 2.2.3 Bromide.... ................................ 10 Figure 3: Zirconium crystal bar process flow diagram. .............................................. 19 Figure 4: Examples of crystal bar produced using the iodide volatilization process. (A) Titanium. (B) Zirconium. (C) Hafnium. (D...

Parkison, Adam J

2013-06-04

241

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

242

Manganese porphyrin multilayer films assembled on ITO electrodes via zirconium phosphonate chemistry: chemical and electrochemical  

E-print Network

Manganese porphyrin multilayer films assembled on ITO electrodes via zirconium phosphonate University, 2145 Sheridan Road, Evanston, IL 60208-3113 A supported manganese porphyrin-based oxidation)porphyrinato] manganese(III) chloride (2) and zirconium(IV) ions on indium­tin oxide electrodes. This assembly technique

243

Zirconium carbide as an electrocatalyst for the chromous-chromic redox couple  

NASA Technical Reports Server (NTRS)

Zirconium carbide is used as a catalyst in a REDOX cell for the oxidation of chromous ions to chromic ions and for the reduction of chromic ions to chromous ions. The zirconium carbide is coated on an inert electronically conductive electrode which is present in the anode fluid of the cell.

Gahn, R. F.; Reid, M. A.; Yang, C. Y. (inventors)

1981-01-01

244

Zirconium oxidation under high energy heavy ion irradiation N. Brerd, A. Chevarier, N. Moncoffre, H. Jaffrezic,  

E-print Network

Zirconium oxidation under high energy heavy ion irradiation N. Bérerd, A. Chevarier, N. Moncoffre This paper concerns the study of zirconium oxidation under irradiation with high energetic Xe ions oxidation data. 1 #12;I. INTRODUCTION This paper deals with the influence of heavy ion irradiation

Paris-Sud XI, Université de

245

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

246

Solid-State Coexistance of (Zr12) and (Zr6) Zirconium Oxocarboxylate Clusters  

SciTech Connect

Ligand metathesis, Co(II) coordination, and partial condensation reactions of an archetypal {Zr6} zirconium oxocarboxylate cluster result in the first example of the coexistence of the distinct zirconium oxide frameworks {Zr6O8} and {Zr12O22}. Even minor modifications to the reaction conditions push this apparent equilibrium towards the {Zr6O8}-based product.

Malaestean, Lurie [RWTH Aachen University; Alici, Meliha Kutluca [RWTH Aachen University; Besson, Claire [RWTH Aachen University; Ellern, Arkady [Ames Laboratory; Kogerler, Paul [RWTH Aachen University

2013-10-30

247

Solid-state coexistence of {Zr12} and {Zr6} zirconium oxocarboxylate clusters  

SciTech Connect

Ligand metathesis, Co(II) coordination, and partial condensation reactions of an archetypal {Zr6} zirconium oxocarboxylate cluster result in the first example of the coexistence of the distinct zirconium oxide frameworks {Zr6O8} and {Zr12O22}. Even minor modifications to the reaction conditions push this apparent equilibrium towards the {Zr6O8}-based product.

Malaestean, Iurie L. [RWTH Aachen University; Alici, Meliha Kutluca [RWTH Aachen University; Besson, Claire [RWTH Aachen University; Ellern, Arkady [Ames Laboratory; Kogerler, Paul [RWTH Aachen University

2013-10-30

248

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

249

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

250

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

251

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

252

Field compatible calibration procedure for peroxyacetyl nitrate  

Microsoft Academic Search

A field compatible calibration procedure for generating ppb levels of peroxyacetyl nitrate is presented. The procedure is based upon the condensed-phase synthesis of peroxyacetyl nitrate (PAN) in octane solution. These solutions show PAN loss of <4% month⁻¹ when stored at -20°C. The dilute PAN solutions are injected directly into known volumes of air in Tedlar bags to obtain ppb gas-phase

Michael W. Holdren; Chester W. Spicer

1984-01-01

253

Microbial uranium immobilization independent of nitrate reduction.  

PubMed

At many uranium processing and handling facilities, including sites in the US Department of Energy (DOE) complex, high levels of nitrate are present as co-contamination with uranium in groundwater. The daunting prospect of complete nitrate removal prior to the reduction of uranium provides a strong incentive to explore bioremediation strategies that allow for uranium bioreduction and stabilization in the presence of nitrate. Typical in situ strategies involving the stimulation of metal-reducing bacteria are hindered by low-pH environments and require that the persistent nitrate must first and continuously be removed or transformed prior to uranium being a preferred electron acceptor. This work investigated the possibility of stimulating nitrate-indifferent, pH-tolerant microorganisms to achieve bioreduction of U(VI) despite nitrate persistence. Enrichments from U-contaminated sediments demonstrated nearly complete reduction of uranium with very little loss of nitrate from pH 5.7-6.2 using methanol or glycerol as a carbon source. Bacterial 16S rRNA genes were amplified from uranium-reducing enrichments (pH 5.7-6.2) and sequenced. Phylogenetic analyses classified the clone sequences into four distinct clusters. Data from sequencing and terminal-restriction fragment length polymorphism (T-RFLP) profiles indicated that the majority of the microorganisms stimulated by these enrichment conditions consisted of low G+C Gram-positive bacteria most closely related to Clostridium and Clostridium-like organisms. This research demonstrates that the stimulation of a natural microbial community to immobilize U through bioreduction is possible without the removal of nitrate. PMID:17686028

Madden, Andrew S; Smith, April C; Balkwill, David L; Fagan, Lisa A; Phelps, Tommy J

2007-09-01

254

Oxidation of pearlitic steels in nitrate solutions  

SciTech Connect

The authors investigated the effect of the temperature, the time of treatment, the concentration, and the pH. They evaluated the protective properties of the oxide films obtained in the treatment of pearlitic steels in nitrate solutions according to the minimal concentration of sodium nitrate necessary for the practically complete suppression of corrosion of the investigated specimens in desalinated water at 20/sup 0/C.

Prozorov, V.V.

1987-11-01

255

Nitrates and detinning in canned carrots  

E-print Network

the Steel Producers-Can Manufacturers Institute-National Canners Association Research Founda- tion on Internal Can Corrosion to encourage the investi- gation of nitrates as a possible causative agent in the rapid detinning of plain tinned containers... accelerated the internal corrosion of the tin plate. He also reported that high levels of nitrates in green beans produced accelerated corrosion of the container. A vari- able response to fertilizer treatments was found in toma- toes; although those...

Florine, Thomas Edward

1968-01-01

256

Thermal decomposition of uranyl nitrate hexahydrate  

Microsoft Academic Search

TG-DTA-EGA studies have shown that anhydrous uranyl nitrate cannot be obtained by thermal decomposition of uranyl nitrate\\u000a hexahydrate. Hydrolysis and polymerization of the salt during dehydration resulted in hydroxynitrates which decomposed in\\u000a multiple steps with the evolution of oxides of nitrogen and water. The extent of hydrolysis dependend on the sample size,\\u000a heating rate and nature of sample containment. Large

K. V. Rajagopalan; P. V. Ravindran; T. P. Radhakrishnan

1995-01-01

257

NITRATE DESTRUCTION LITERATURE SURVEY AND EVALUATION CRITERIA  

Microsoft Academic Search

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

Steimke

2011-01-01

258

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

259

Predicting the equilibria of point defects in zirconium oxide : a route to understand the corrosion and hydrogen pickup of zirconium alloys  

E-print Network

The performance of zirconium alloys in nuclear reactors is compromised by corrosion and hydrogen pickup. The thermodynamics and kinetics of these two processes are governed by the behavior of point defects in the ZrO? layer ...

Youssef, Mostafa Youssef Mahmoud

2014-01-01

260

Lithium-boron anodes in nitrate thermal battery cells  

SciTech Connect

A thermally activated electrochemical cell utilizes a lithium-boron anode and a molten nitrate electrolyte selected from the group consisting of lithium nitrate, a mixture of lithium nitrate and sodium nitrate, a mixture of lithium nitrate and potassium nitrate, and a mixture of lithium nitrate and sodium nitrate with potassium nitrate, to provide improved cell electrical performance. The electrolyte is contained on a fiberglass separator and the electrolyte adjacent to the cathode may contain silver nitrate as well. Current densities over 300 mA/cm/sup 2/ with a usable temperature range of over 150/sup 0/ C. have been obtained. Anode open circuit potentials of about 3.2 V were found with little polarization at 100 mA/cm/sup 2/ and with very slight polarization at 300 mA/cm/sup 2/.

McManis III, G. E.; Fletcher, A. N.; Miles, M. H.

1985-08-13

261

Zirconium Determination by Cooling Curve Analysis during the Pyroprocessing of Used Nuclear Fuel  

SciTech Connect

An alternative method to sampling and chemical analyses has been developed to monitor the concentration of zirconium in real-time during the casting of uranium products from the pyroprocessing of used nuclear fuel. The method utilizes the solidification characteristics of the uranium products to determine zirconium levels based on standard cooling curve analyses and established binary phase diagram data. Numerous uranium products have been analyzed for their zirconium content and compared against measured zirconium data. From this data, a relationship was derived that incorporates the mass dependency of the uranium products since solidification monitoring is performed external to the melt. Using the relationship, a reasonable fit of calculated to measured zirconium content was established considering the errors in the system.

B.R. Westphal; J.C. Price; K.J. Bateman; K.C. Marsden

2001-03-01

262

Effects of intermetallic particles on the SCC initiation of zirconium alloys  

NASA Astrophysics Data System (ADS)

In order to investigate effects of intermetallic particles on SCC initiation of zirconium alloys, tensile tests were conducted in an iodine atmosphere using zirconium plates with different amounts of impurities, and Zircaloy-2 plates. SCC susceptibility of zirconium increased significantly with its iron content. Even small amounts of iron could form the intermetallic compound ZrFe 2 whose particle size and number increased with iron content. In the case of Zircaloy-2, two different types of ternary compounds were detected, namely Zr(CrFe) 2 and Zr 2(NiFe). Metallographic examinations showed that the particles located at grain boundaries were important sites of SCC initiation in zirconium alloys. The initiation probability increased significantly with the amount of the particles, which supported the strong correlation between SCC susceptibility of zirconium and its iron content.

Kubo, T.; Wakashima, Y.; Imahashi, H.; Nagai, M.

1985-06-01

263

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

264

Preparation and properties of uniform mixed and coated colloidal particles. Part 5. Zirconium compounds  

SciTech Connect

Colloidal dispersions of uniform spherical particles by zirconium basic sulphate and zirconium oxy-basic carbonate were prepared by ageing zirconium sulphate solutions at elevated temperatures in the presence of urea. Different chemical compositions of the above products resulted when the ageing temperature was altered. Depending on the nature of the original solids, calcination at 800 C resulted in the formation of tetragonal or monoclinic zirconia. Under certain conditions a mixed phase, including cubic zirconia, has also been identified. The particle morphology was retained during these transformations. Coprecipitation in mixed solutions of zirconium and yttrium salts aged at 80 C yielded composite spherical particles of basic carbonate with a zirconium to yttrium ratio of the solid similar to that used in the initial solution.

Alken, B.; Hsu, W.P.; Matijevic, E.

1990-01-01

265

[Photodegradation of atenolol in aqueous nitrate solution].  

PubMed

The aqueous photolysis of beta-blocker atenolol (ATL) using Xe lamp as simulated solar irradiation source was investigated in the presence of nitrate ions. The effects of nitrate ion concentration, solution pH value, and concentration of bicarbonate and humic substance on the photodegradation of ATL were studied. The results showed that photodegradation of ATL in nitrate solution followed pseudo-first-order kinetics. The increasing concentration of nitrate ion promoted the photodegradation rate of ATL. The first-order rate constant increased from 0.002 26 min(-1) to 0.009 4 min(-1) with nitrate concentration increasing from 0 to 5 mmol x L(-1). Acidic or alkaline condition of the solution favored the photodegradation of ATL. Different concentration of bicarbonate showed insignificant effect of the degradation while the increasing concentration of fulvic acid showed inhibiting effect. Hydroxyl radical was determined to be formed during the photolysis process of ATL using isopropanol as molecular probe. The main photoproducts of ATL were identified by using SPE-LC-MS techniques and possible photoinduced degradation pathways in nitrate solution were proposed. PMID:22509585

Ji, Yue-Fei; Zeng, Chao; Meng, Cui; Yang, Xi; Gao, Shi-Xiang

2012-02-01

266

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

267

Thermodynamic study of the zirconium-aluminum system  

SciTech Connect

The heats of formation of the zirconium-aluminum intermetallic compounds ZrAl/sub 3/, ZrAl/sub 2/, Zr/sub 2/Al/sub 3/, ZrAl, Zr/sub 5/Al/sub 4/, Zr/sub 3/Al/sub 2/, Zr/sub 5/Al/sub 3/, and the solid solution of aluminum in bcc zirconium have been studied using a Knudsen cell mass spectrometric technique. The high temperature compound Zr/sub 5/Al/sub 4/ was identified in the residue of some of these experiments and this led to further heat treatment/X-ray diffraction experiments which indicated that Zr/sub 4/Al/sub 3/, previously reported to form from the melt, decomposes in the solid state at temperature in excess of 1050/sup 0/C. By measuring aluminum vapor pressures over the two-phase ranges of the system from 0 < X/sub Al/ < 0.75 the enthalpy changes for the decomposition reactions were determined by second- and third-law methods, and these were used along with the measured vapor pressure of aluminum over the solid solution of aluminum in bcc zirconium to derive the enthalpies of formation of the intermetallic phases (in kcal/mole): ZrAl/sub 3/, -38.96; ZrAl/sub 2/, -32.86; Zr/sub 2/Al/sub 3/, -56.12; ZrAl, -21.36; Zr/sub 5/Al/sub 4/, -93.76; Zr/sub 3/Al/sub 2/, -48.78; Zr/sub 5/Al/sub 3/, -74.57. 21 references, 4 figures, 4 tables.

Kematick, R.J.; Franzen, H.F.

1984-09-01

268

The abundances of zirconium and hafnium in the solar system  

NASA Technical Reports Server (NTRS)

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 Zr and Hf. Orgueil contains 3.1 ppm Zr and 0.11 ppm Hf, corresponding to 9.0 and 0.16 atoms, respectively, relative to 1 million Si atoms.

Ganapathy, R.; Papia, G. M.; Grossman, L.

1976-01-01

269

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

270

Rapid and cost-effective method for synthesizing zirconium silicides  

Microsoft Academic Search

An experimental study on the preparation of zirconium silicides was conducted using ZrSiO4–Mg, ZrSiO4–SiO2–Mg and ZrSiO4–ZrO2–Mg powder mixtures by the combustion synthesis (CS) technique. Test specimens having different composition ratios including Zr:Si=1:2, 1:1, 5:4, 5:3, 2:1, and 3:1 were employed in this study. Temperature profiles relative to all the starting compositions were measured using thermocouples, and the values of the

Il-Je Cho; Kyung-Tae Park; Sang-Ki Lee; Hayk H. Nersisyan; Yong-Soo Kim; Jong-Hyeon Lee

2010-01-01

271

Bulk Hydrides and Delayed Hydride Cracking in Zirconium Alloys  

NASA Astrophysics Data System (ADS)

Zirconium alloys are susceptible to engineering problems associated with the uptake of hydrogen throughout their design lifetime in nuclear reactors. Understanding of hydrogen embrittlement associated with the precipitation of brittle hydride phases and a sub-critical crack growth mechanism known as Delayed Hydride Cracking (DHC) is required to provide the engineering justifications for safe reactor operation. The nature of bulk zirconium hydrides at low concentrations (< 100 wt. ppm) is subject to several contradictory descriptions in the literature associated with the stability and metastability of gamma-phase zirconium hydride. Due to the differing volume expansions (12-17%) and crystallography between gamma and delta hydride phases, it is suggested that the matrix yield strength may have an effect on the phase stability. The present work indicated that although yield strength can shift the phase stability, other factors such as microstructure and phase distribution can be as or more important. This suggests that small material differences are the reason for the literature discrepancies. DHC is characterised by the repeated precipitation, growth, fracture of brittle hydride phases and subsequent crack arrest in the ductile metal. DHC growth is associated primarily the ability of hydrogen to diffuse under a stress induced chemical potential towards a stress raiser. Knowledge of the factors controlling DHC are paramount in being able to appropriately describe DHC for engineering purposes. Most studies characterise DHC upon cooling to the test temperature. DHC upon heating has not been extensively studied and the mechanism by which it occurs is somewhat controversial in the literature. This work shows that previous thermo-mechanical processing of hydrided zirconium can have a significant effect on the dissolution behaviour of the bulk hydride upon heating. DHC tests with gamma-quenched, furnace cooled-delta and reoriented bulk hydrides upon heating and DHC upon cooling suggest that the amount of hydrogen in solution is the primary factor controlling the occurrence of DHC and consistent with the postulation that the stress induced chemical potential is the driving force for DHC.

Tulk, Eric F.

272

Nitrate reductase activity in corn seedlings as affected by light and nitrate content of nutrient media  

Microsoft Academic Search

Young corn plants placed in complete darkness for 48 hours lost 90% of their nitrate reductase activity. The activity was quickly restored when the plants were returned to the light. In other experiments, corn plants were grown under artificial shade in the greenhouse. The nitrate reductase activity in these plants decreased roughly in proportion to the amount of shading. It

R. H. Hageman; D. Flesher

1960-01-01

273

Solubility of uranyl nitrate in nitric acid solutions of aluminum nitrate  

Microsoft Academic Search

The solubility of uranyl nitrate in nitric acid solutions of aluminum nitrate at 25°C containing 10, 20 and 30 mass % of nitric acid has been studied by the isothermal method. The Schreinemakers method has been used to establish the composition of the solid phases, which has been confirmed by crystallographic and thermographic studies. Data are presented on the viscosity

B. K. Medkov; M. R. Petrov; O. N. Roslyakova

1988-01-01

274

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...

275

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

PubMed

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 (70-99%) and soil denitrification rates (3.78-15.02 microg N2O-N/g dry soil/h) than an unplanted covered wetland cell (1%, 0.11 microg N2O-N/g/h). However, the unplanted uncovered wetland cell showed a nitrate removal efficiency (55%) lower than but a soil denitrification rate (9.12 microg N2O-N/g/h) comparable to the planted cells. The nitrate removal rate correlated closely and positively with the soil denitrification rate for the planted cells, indicating that soil denitrification is an important process for removing nitrate in constructed wetlands. The results of nitrogen budget revealed that around 68.9-90.7% of the overall nitrogen removal could be attributed to the total denitrification. The soil denitrification rate was found to correlate significantly (P < 0.01) with the extractable organic carbon, organic matter, and in situ-measured redox potential of wetland soil, which accordingly were concluded as suitable indicators of soil denitrification rate and nitrate removal rate in nitrate treatment wetlands. PMID:17365317

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

2007-03-01

276

Suppression of erythropoiesis by dietary nitrate.  

PubMed

In mammals, hypoxia-triggered erythropoietin release increases red blood cell mass to meet tissue oxygen demands. Using male Wistar rats, we unmask a previously unrecognized regulatory pathway of erythropoiesis involving suppressor control by the NO metabolite and ubiquitous dietary component nitrate. We find that circulating hemoglobin levels are modulated by nitrate at concentrations achievable by dietary intervention under normoxic and hypoxic conditions; a moderate dose of nitrate administered via the drinking water (7 mg NaNO3/kg body weight/d) lowered hemoglobin concentration and hematocrit after 6 d compared with nonsupplemented/NaCl-supplemented controls. The underlying mechanism is suppression of hepatic erythropoietin expression associated with the downregulation of tissue hypoxia markers, suggesting increased pO2. At higher nitrate doses, however, a partial reversal of this effect occurred; this was accompanied by increased renal erythropoietin expression and stabilization of hypoxia-inducible factors, likely brought about by the relative anemia. Thus, hepatic and renal hypoxia-sensing pathways act in concert to modulate hemoglobin in response to nitrate, converging at an optimal minimal hemoglobin concentration appropriate to the environmental/physiologic situation. Suppression of hepatic erythropoietin expression by nitrate may thus act to decrease blood viscosity while matching oxygen supply to demand, whereas renal oxygen sensing could act as a brake, averting a potentially detrimental fall in hematocrit.-Ashmore, T., Fernandez, B. O., Evans, C. E., Huang, Y., Branco-Price, C., Griffin, J. L., Johnson, R. S., Feelisch, M., Murray, A. J. Suppression of erythropoiesis by dietary nitrate. PMID:25422368

Ashmore, Tom; Fernandez, Bernadette O; Evans, Colin E; Huang, Yun; Branco-Price, Cristina; Griffin, Julian L; Johnson, Randall S; Feelisch, Martin; Murray, Andrew J

2015-03-01

277

Evaluation of the resistance of irradiated zirconium-liner cladding to iodine-induced stress corrosion cracking  

NASA Astrophysics Data System (ADS)

An evaluation was made of irradiated zirconium-liner cladding for its resistance to iodine-induced stress corrosion cracking (SCC). Emphasis was put on irradiation-induced hardening in zirconium and SCC resistance in zirconium-liner cladding as compared with Zircaloy-2 cladding. The Vickers microhardness test revealed that crystal bar zirconium experienced less hardening than Zircaloy-2 during neutron exposure. The SCC resistance of zirconium-liner cladding was evaluated for failure strains under the tube pressurization SCC test, and compared with the results of Zircaloy-2 cladding. The failure strains of zirconium-liner cladding were significantly larger than those of Zircaloy-2 cladding over all neutron fluence ranges examined, e.g., more than ten times at 1.0 × 10 21n/ cm2 ( E > 1 MeV). Judging from our results on the Vickers microhardness and SCC tests, good SCC resistance of zirconium-liner cladding could be expected even at high fluences.

Shimada, Sachio; Nagai, Masayuki

1983-02-01

278

The effect of some ammonium salts on nitrate reductase level, on in vivo nitrate reduction and on nitrate content in excised pisum sativum roots  

Microsoft Academic Search

The effect of some ammonium salts on nitrate reductase (NR) level, onin vivo nitrate reduction and on nitrate content was followed in the presence of nitrate in the medium, under changing experimental\\u000a conditions, in excisedPisum sativum roots, and their effect was compared with that of KNO3, Ca(NO3)2 and NaNO3 at 15 mM NO3\\u000a - concentration, i.e. at a concentration which

J. Sahulka

1977-01-01

279

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

280

Microbial Reduction of Chromate in the Presence of Nitrate by Three Nitrate Respiring Organisms  

PubMed Central

A major challenge for the bioremediation of toxic metals is the co-occurrence of nitrate, as it can inhibit metal transformation. Geobacter metallireducens, Desulfovibrio desulfuricans, and Sulfurospirillum barnesii are three soil bacteria that can reduce chromate [Cr(VI)] and nitrate, and may be beneficial for developing bioremediation strategies. All three organisms respire through dissimilatory nitrate reduction to ammonia (DNRA), employing different nitrate reductases but similar nitrite reductase (Nrf). G. metallireducens reduces nitrate to nitrite via the membrane bound nitrate reductase (Nar), while S. barnesii and D. desulfuricans strain 27774 have slightly different forms of periplasmic nitrate reductase (Nap). We investigated the effect of DNRA growth in the presence of Cr(VI) in these three organisms and the ability of each to reduce Cr(VI) to Cr(III), and found that each organisms responded differently. Growth of G. metallireducens on nitrate was completely inhibited by Cr(VI). Cultures of D. desulfuricans on nitrate media was initially delayed (48?h) in the presence of Cr(VI), but ultimately reached comparable cell yields to the non-treated control. This prolonged lag phase accompanied the transformation of Cr(VI) to Cr(III). Viable G. metallireducens cells could reduce Cr(VI), whereas Cr(VI) reduction by D. desulfuricans during growth, was mediated by a filterable and heat stable extracellular metabolite. S. barnesii growth on nitrate was not affected by Cr(VI), and Cr(VI) was reduced to Cr(III). However, Cr(VI) reduction activity in S. barnesii, was detected in both the cell free spent medium and cells, indicating both extracellular and cell associated mechanisms. Taken together, these results have demonstrated that Cr(VI) affects DNRA in the three organisms differently, and that each have a unique mechanism for Cr(VI) reduction. PMID:23251135

Chovanec, Peter; Sparacino-Watkins, Courtney; Zhang, Ning; Basu, Partha; Stolz, John F.

2012-01-01

281

Molecular Components of Nitrate and Nitrite Efflux in Yeast  

PubMed Central

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; de la Rosa, Diego Alvarez

2014-01-01

282

Nitrate reductase activity and protein concentration of two populas clones.  

PubMed

Nitrate reductase activity and protein percentage of various tree parts of two Populus clones were determined in relation to nitrate ion activity. Nitrogen was supplied as NH(4)NO(3) in a nutriculture system. Wisconsin-5 had significantly greater nitrate reductase activity than Tristis No. 1. Protein percentages of leaf plastochron index 10 leaves (tenth leaf below first leaf lamina exceeding 20 mm in length), bottom leaves, and roots in relation to nitrate ion activity were not appreciably different between clones. The nitrate reductase activity and protein percentage of Tristis No. 1 apex started to level off at the same nitrate ion activity, about 0.09 mm. In Wisconsin-5 apex protein percentage continued to increase at nitrate ion activities where nitrate reductase activity decreases sharply, suggesting that protein nitrogen was being supplied by ammonium ion. The difference in nitrate reductase activity between clones was probably due to genetically determined ability to synthesize nitrate reductase in response to nitrate ion. The expression of nitrate reductase activity was not an index of nitrogen assimilation ability but may be a useful index of growth potential when nitrate ion does not limit nitrate reductase synthesis. PMID:16658755

Dykstra, G F

1974-04-01

283

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

284

Nucleation and growth kinetics of zirconium-oxo-alkoxy nanoparticles.  

PubMed

Nucleation and growth of zirconium-oxo-alkoxy (ZOA) nanoparticles were studied in a sol-gel process in n-propanol solution at a hydrolysis ratio H between 1.0 and 2.7 and zirconium-n-propoxyde precursor concentrations between 0.10 and 0.15 mol l(-1). The chemical transformations were conducted in quasi-perfect micromixing conditions (Damköhler number Da ? 1) and the nanoparticle size evolution was monitored in situ with the light scattering method. The size of primary nanoparticles (nuclei) 2R0 = 3.6 nm was found to be almost independent of the preparation conditions. A remarkable similarity with the titanium-oxo-alkoxy (TOA) nanoparticles was observed. In particular, both systems show the induction stage of the sol-gel growth for a hydrolysis ratio H > 2.0 and stable oxometallate units for H? 2.0. However in contrast to TOA, no stable hierarchical ZOA units (clusters) with R0?R? 1.0 nm were observed, which makes this system less stable against aggregation, leading to polydispersed nanoparticles. PMID:25502510

Labidi, Sana; Jia, Zixian; Amar, Mounir Ben; Chhor, Khay; Kanaev, Andrei

2015-01-28

285

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

286

Zirconium speciation in lactate solutions and polyacrylate gels.  

PubMed

Controlling gelation kinetics is an important objective for several applications (ceramic and thin film syntheses, reduction in permeability of porous rock, etc). There is a growing interest in studying the gelation of polymers by zirconium, a crosslinker of lower toxicity than the chromium which is still commonly used. XAS at the Zr K-edge was performed at the European Synchrotron Radiation Facility (ESRF) on the BM32 beamline. The fluorescence detection was used to carry out successful in situ speciation at concentrations as low as 36 ppm. The Zr speciation was determined both in ZrLa (where La stands for lactate) aqueous solutions and in gels of a terpolymer of acrylamide having 2% of zirconium reactive acrylate side groups and 2% of sulfonate groups introduced to prevent syneresis. XANES results show that Zr is always in a dodecahedral geometry. In ZrLa solutions. EXAFS results indicate that Zr species grow from a dimer Zr2(La)6 to a tetramer (Zr4(La)x) and then to larger polymers resulting from tetramer associations, as the Zr concentration decreases from 51840 ppm to 36ppm. In polymer gels, Zr species appear to be dimers at pH 6 while tetramers are found when gelation occurred at pH 7. Calculations taking into account multiple scattering effects as well as dynamic molecular calculation confirmed conclusions derived from conventional EXAFS analysis. PMID:11512896

Rose, J; Chauveteau, G; Tabary, R; Renard, M; Omari, A; Toulhoat, H

2001-03-01

287

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

288

Vulnerability of streams to legacy nitrate sources.  

PubMed

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). PMID:23530900

Tesoriero, Anthony J; Duff, John H; Saad, David A; Spahr, Norman E; Wolock, David M

2013-04-16

289

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

PubMed

Little is known about the effect of dietary nitrate on the nitrate/nitrite/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 4-period crossover controlled design. We hypothesized that the high-nitrate diet would show higher levels of plasma nitrate/nitrite and lower blood pressure compared with the control diet, which would be potentiated by the supplement. Participants were 8 normotensive older men and women (5 female, 3 male, 72.5 ± 4.7 years old) with no overt disease or medications that affect nitric oxide metabolism. Plasma nitrate and nitrite levels and blood pressure were measured before 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 < .001 and P = .017 for nitrate and nitrite, respectively) and high-nitrate diet + supplement (P = .001 and P = .002), but not for control diet (P = .713 and P = .741) or high-nitrate diet (P = .852 and P = .500). Blood pressure decreased from the morning baseline measure to the three 2-hour postmeal 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. PMID:22464802

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

2012-03-01

290

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

291

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.

Larry Johnson

292

A novel ultrasonication method in the preparation of zirconium impregnated cellulose for effective fluoride adsorption.  

PubMed

In the present work, we propose for the first time a novel ultrasound assisted methodology involving the impregnation of zirconium in a cellulose matrix. Fluoride from aqueous solution interacts with the cellulose hydroxyl groups and the cationic zirconium hydroxide. Ultrasonication ensures a green and quick alternative to the conventional time intensive method of preparation. The effectiveness of this process was confirmed by comprehensive characterization of zirconium impregnated cellulose (ZrIC) adsorbent using Fourier transform infrared spectroscopy (FT-IR), energy dispersive X-ray spectrometry (EDX) and X-ray diffraction (XRD) studies. The study of various adsorption isotherm models, kinetics and thermodynamics of the interaction validated the method. PMID:24394388

Barathi, M; Kumar, A Santhana Krishna; Rajesh, N

2014-05-01

293

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

294

Thermodynamic Analysis and Growth of Zirconium Carbide by Chemical Vapor Deposition  

NASA Astrophysics Data System (ADS)

Equilibrium calculations were used to optimize conditions for the chemical vapor deposition of zirconium carbide from zirconium halide + CxHy+H2+Ar system. The results show the CVD-ZrC phase diagram is divided into ZrC+C, ZrC and ZrC+Zr zones by C, Zr generating lines. For the same mole of ZrCl4 reactant, it needs higher concentration of CH4 to generate single ZrC phase than that of C3H6. Using these calculations as a guide, single-phase cubic zirconium carbide coatings were deposited onto graphite substrate.

Wei, Sun; Hua, Hao Zheng; Xiang, Xiong

295

Thermolysis of Urea Complexes of Uranyl Nitrate  

Microsoft Academic Search

Quantitative parameters of thermolysis of uranyl nitrate urea complexes, [UO2(NO3)2{(NH2)2CO}2], [UO2(H2O){(NH2)2CO}4](NO3)2, and [UO2(H2O){(NH2)2CO}5](NO3)2 at 175, 200, and 225C were measured. Thermolysis of [UO2(NO3)2{(NH2)2CO}2] at 200C affords the biuret complex of uranyl nitrate in a 90% yield. The urea ligands in the hydrated complexes completely\\u000a transform into biuret at 175C. Thermolysis of [UO2(H2O){(NH2)2CO}5](NO3)2 yields the biuret-cyanurate complexes of uranyl nitrate. The

N. N. Kostyuk

2005-01-01

296

Halide Ion Enhancement of Nitrate Ion Photolysis  

NASA Astrophysics Data System (ADS)

Nitrate ion photochemistry is an important source of NOx in the polar regions. It is uncertain whether coexisting ions such as halides play a role in nitrate photochemistry. The effect of halides on NO3 photolysis was investigated using photolysis experiments in 230 L Teflon chambers that contain deliquesced aerosols of NaBr:NaNO3, KBr:KNO3 and ternary mixtures of NaCl:NaBr:NaNO3. Gas phase NO2 and gaseous halogen products were measured as a function of photolysis time using long path FTIR, NOx chemiluminescence and API-MS (atmospheric pressure ionization mass spectrometry). Experiments were conducted with NO3- held at a constant 0.5 M and with the amount of total halide concentration varying from 0.25 M to 4 M. Studies on NaBr:NaNO3 mixtures suggest that as the bromide ion to nitrate ion ratio increases, there is an enhancement in the rate of production of NO2 in the nitrate-bromide mixtures over that formed in the photolysis of NaNO3. Molecular dynamic (MD) simulations provide molecular level insight into the ions near the air-water interface in the aqueous halide-nitrate mixtures. These studies suggest that the presence of sodium halides at the air-water interface may encourage some nitrate ions to approach the top layers of water, allowing for more efficient escape of photoproducts than is seen in the absence of halides. Experiments on mixtures of KBr:KNO3 are being conducted to determine potential cation effects. In addition, ternary mixtures of NaCl:NaBr:NaNO3 are being examined to determine the effects of mixtures of halides on production of NO2 and gaseous halogen products. The implications of this photochemistry for tropospheric chemistry will be discussed.

Richards, N. K.; Wingen, L. M.; Callahan, K. M.; Tobias, D. J.; Finlayson-Pitts, B. J.

2009-12-01

297

Effect of nitrate and incubation conditions on the production of catalase and nitrate reductase by staphylococci.  

PubMed

The objective of this work was to study the production of catalase and nitrate reductase by staphylococci in order to understand their role in lipid oxidation during sausage manufacturing. Catalase and nitrate reductase were measured in resting cells and supernatants of staphylococci grown in different conditions. All staphylococci (except S. warneri) synthetized nitrate reductase. In static condition, the synthesis was maximal during exponential growth phase, whereas in shaking condition, the synthesis was maximal at the beginning of stationary phase. The production of nitrate reductase was increased in presence of nitrate, this effect was particularly important for the two S. carnosus strains which exhibited the highest activity. For all staphylococci, the production of catalase was maximal at the end of the exponential growth phase. The lowest amount of catalase was produced by S. warneri and the highest by S. carnosus. Only S. xylosus 873 and S. saprophyticus 852 released high amounts of catalase in the supernatant growth. Staphylococci produced higher amounts of catalase in shaking conditions. Addition of nitrate in the growth media favoured the synthesis of catalase, with a pronounced effect for S. carnosus. Nitrate also favoured the release of catalase. PMID:10573391

Talon, R; Walter, D; Chartier, S; Barrière, C; Montel, M C

1999-11-01

298

Field compatible calibration procedure for peroxyacetyl nitrate  

SciTech Connect

A field compatible calibration procedure for generating ppb levels of peroxyacetyl nitrate is presented. The procedure is based upon the condensed-phase synthesis of peroxyacetyl nitrate (PAN) in octane solution. These solutions show PAN loss of <4% month/sup -1/ when stored at -20/sup 0/C. The dilute PAN solutions are injected directly into known volumes of air in Tedlar bags to obtain ppb gas-phase concentrations. The addition of low levels of NO/sub 2/ into the bags stabilizes PAN in the gas phase.

Holdren, M.W.; Spicer, C.W.

1984-02-01

299

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

300

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

301

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

302

COGEMA Experience in Uranous Nitrate Preparation  

SciTech Connect

Separation and purification of plutonium by PUREX process is based on a sequence of extraction and back extraction which requires reducing plutonium Pu IV (extractable form) into Pu III (inextractable form) Different reducers can be used to reduce Pu IV into Pu III. Early plants such as that for Magnox fuel at Sellafield used ferrous sulfamate while UP 1 at Marcoule used uranous sulfamate. These reducers are efficient and easy to prepare but generates ferric and/or sulphate ions and so complicates management of the wastes from the plutonium purification cycle. Recent plants such as UP3 and UP2 800 at La Hague, THORP at Sellafield, and RRP at Rokkasho Mura (currently under tests) use uranous nitrate (U IV) stabilized by hydrazinium nitrate (N{sub 2}H{sub 5}NO{sub 3}) and hydroxyl ammonium nitrate (HAN). In the French plants, uranous nitrate is used in U-Pu separation and alpha barrier and HAN is used in Pu purification. Compared to sulfamate, U IV does not generate extraneous chemical species and uranyl nitrate (U VI) generated by reducing Pu IV follows the main uranium stream. More over uranous nitrate is prepared from reprocessed purified uranyl nitrate taken at the outlet of the reprocessing plant. Hydrazine and HAN offer the advantage to be salt-free reagents. Uranous nitrate can be generated either by electrolysis or by catalytic hydrogenation process. Electrolytic process has been implemented in early plant UP 1 at Marcoule (when changing reducer from uranous sulfamate to uranous nitrate) and was used again in UP2 plant at La Hague. However, the electrolytic process presented several disadvantages such as a low conversion rate and problems associated with the use of mercury. Electrolysis cells with no mercury were developed for the Eurochemic plant in Belgium and then implemented in the first Japanese reprocessing plant in Tokai-Mura. But finally, in 1975, the electrolytic process was abandoned in favor of the catalytic hydrogenation process developed at La Hague. The yield of the operation and its simplicity were the main reasons for this choice. Nowadays, our catalytic hydrogenation process is used in all the commercial reprocessing plants worldwide: THORP at Sellafield, UP3 and UP2 800 at La Hague, and RRP at Rokkasho-Mura. In this process, uranyl nitrate is reduced to uranous nitrate by hydrogen in presence of a platinum based catalyst. Most of the plants implement the reaction in the same kind of reactor: 'co-current, up-flow and fixed-bed reactor'. For UP2 800 at La Hague, started in 1994, a new kind of reactor allowing a higher capacity has been developed. In this reactor, the catalyst bed is not fixed but circulating (fluidized bed). The aim of the paper is to describe both reactor technology implemented in La Hague (fixed bed and fluidized bed), to show their performance in terms of capacity and yield and to compare their operating and maintenance principles. (authors)

Tison, E. [COGEMA, AREVA Group, Etablissement de La Hague, 50440 Beaumont La Hague Cedex (France); Bretault, Ph. [SGN, AREVA Group, 1 rue des Herons, 78182 St Quentin Yvelines Cedex (France)

2006-07-01

303

Physiologie vgtale Mesure de l'activit nitrate rductase  

E-print Network

/ Rhizobium/ symbiose Summary — Measurement of nitrate reductase activity during the soybean (Glycine / nitrate / nodosity / Rhizobium / symbiosis * Correspondance et tirés à part #12;INTRODUCTION Au champ, les

Paris-Sud XI, Université de

304

ORNL/TM-2008/048 Uranyl Nitrate Flow Loop  

E-print Network

ORNL/TM-2008/048 Uranyl Nitrate Flow Loop October 2008 Jennifer L. Ladd-Lively #12;DOCUMENT Government or any agency thereof. #12;ORNL/TM-2008/048 Nuclear Science and Technology Division URANYL NITRATE

Pennycook, Steve

305

Functionalized Zirconium Phosphate Nano Platelets - From Surface Design to Drug Delivery  

E-print Network

the intended target or compartment. This dissertation will focus on the analytical characterization of zirconium phosphate (ZrP) in both alpha and theta phases as a drug delivery matrix utilizing multiple unique and novel analytical techniques. In the first...

Mukherjee, Atashi

2014-05-30

306

Zirconium Minerals from Mars, Moon and Earth Indicate Crustal 'Refugia' on Early Bombardment Surfaces  

NASA Astrophysics Data System (ADS)

A comparison of the shock microstructural and U-Pb histories of zirconium minerals from the bombardment epoch of Mars, Moon and Earth points to perseverance of early planetary crustal domains throughout the large impactor flux.

Moser, D. E.

2015-02-01

307

Methods for Investigating Gas Bubble Formation in Uranium-Zirconium Alloys  

E-print Network

Uranium-zirconium alloy nuclear fuels have many advantages as compared with ceramic fuels, especially for fast reactor systems. However, metallic fuels aren’t currently used in commercial power production due in part to issues with fuel swelling...

Mews, Kathryn Ann Wright

2013-05-06

308

21 CFR 700.16 - Use of aerosol cosmetic products containing zirconium.  

Code of Federal Regulations, 2012 CFR

... 2012-04-01 false Use of aerosol cosmetic products containing zirconium. 700.16...HEALTH AND HUMAN SERVICES (CONTINUED) COSMETICS GENERAL Requirements for Specific Cosmetic Products § 700.16 Use of aerosol...

2012-04-01

309

21 CFR 700.16 - Use of aerosol cosmetic products containing zirconium.  

Code of Federal Regulations, 2011 CFR

... 2010-04-01 true Use of aerosol cosmetic products containing zirconium. 700.16...HEALTH AND HUMAN SERVICES (CONTINUED) COSMETICS GENERAL Requirements for Specific Cosmetic Products § 700.16 Use of aerosol...

2011-04-01

310

21 CFR 700.16 - Use of aerosol cosmetic products containing zirconium.  

Code of Federal Regulations, 2014 CFR

... 2014-04-01 false Use of aerosol cosmetic products containing zirconium. 700.16...HEALTH AND HUMAN SERVICES (CONTINUED) COSMETICS GENERAL Requirements for Specific Cosmetic Products § 700.16 Use of aerosol...

2014-04-01

311

21 CFR 700.16 - Use of aerosol cosmetic products containing zirconium.  

Code of Federal Regulations, 2013 CFR

... 2013-04-01 false Use of aerosol cosmetic products containing zirconium. 700.16...HEALTH AND HUMAN SERVICES (CONTINUED) COSMETICS GENERAL Requirements for Specific Cosmetic Products § 700.16 Use of aerosol...

2013-04-01

312

Synthesis and catalytic activity of titanium and zirconium chiral diolate complexes  

SciTech Connect

New mono-cyclopentadienyl complexes of titanium and zirconium which contain a chiral diolate have been synthesized. Catalytic enantioselective C-C bond forming reactions will be discussed along with the structural characteristics of the catalyst precursors.

Grumbine, S.K.; Clark, D.L.; Scott, B.; Watkin, J.G. [Los Alamos National Laboratory, NM (United States)

1996-10-01

313

Some characteristics of nitrate reductase induction in Lemna minor L  

Microsoft Academic Search

Low levels of nitrate reductase can be detected in plants of Lemna minor grown on some organic nitrogen sources. Nitrogen-starvation does not lead to a derepression of nitrate reductase activity. Nitrate ions are necessary for the development of maximum enzyme activity and the maintenance of high enzyme levels. Nitrogen-starvation of ammonia-grown plants increases the subsequent rate of nitrate-mediated induction. It

T. O. Orebamjo; G. R. Stewart

1974-01-01

314

76 FR 46907 - Ammonium Nitrate Security Program  

Federal Register 2010, 2011, 2012, 2013, 2014

...terrorism.'' Section II.A of this preamble provides...impacts of their rules on small entities. The RFA covers...of the proposed rule on small entities. Below is a...nitrate, see sections II.D.1 and 2 of this...this rule. 2. Affected Small Business Population...

2011-08-03

315

Ammonium and nitrate tolerance in lichens  

Microsoft Academic Search

Since lichens lack roots and take up water, solutes and gases over the entire thallus surface, these organisms respond more sensitively to changes in atmospheric purity than vascular plants. After centuries where effects of sulphur dioxide and acidity were in the focus of research on atmospheric chemistry and lichens, recently the globally increased levels of ammonia and nitrate increasingly affect

Markus Hauck

2010-01-01

316

NITRATE LEACHING IN FLORIDA URBAN ENVIRONMENTS  

E-print Network

Selection of Dynamic Factor Models Based on Performance Coefficients Ritter (2007 mg/L. Nitrate concentrations above 4 mg/L can affect human activities and the United States Environmental Protection Agency has established 10 mg/L as the maximum contamination level (Nolan, 2001

Ma, Lena

317

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

318

Factors affecting potato petiole sap nitrate tests  

Microsoft Academic Search

Many factors can affect the nitrate?nitrogen concentration of potato petioles. They include but are not limited to the following: N?fertilizer applications, mineralizable soil N, time of sampling, position of the petiole on the plant, age of the plant, potato cultivar, time of the day when plants are sampled, and the environmental conditions prior to sampling. A better understanding of these

Maurice L. Vitosh; George H. Silva

1996-01-01

319

Elevated plasma nitrate levels in depressive states  

Microsoft Academic Search

Background: Previous studies have shown that nitric oxide (NO) synthase inhibitors show preclinical antidepressant-like properties, suggesting that NO is involved in the pathogenesis of depression. The purpose of this study is to examine whether or not NO production increases in depressed patients. Methods: Plasma nitrate concentrations, an index of NO production, were measured by high-performance liquid chromatography in depressed patients

Eiji Suzuki; Gohei Yagi; Toshio Nakaki; Shigenobu Kanba; Masahiro Asai

2001-01-01

320

Iron, nitrate uptake by phytoplankton, and mermaids  

Microsoft Academic Search

The critque by Martin et al. (this issue) of my recalculation of rates of nitrate uptake, and hence of algal division, from the Gulf of Alaska is shown to be incorrect. Neither can iron deficiency, if any, be shown to be connected with the demise of mermen and mermaids, although for different reasons.

Karl Banse

1991-01-01

321

Nitrates, Nitrites, and Health. Bulletin 750.  

ERIC Educational Resources Information Center

This review is intended to assess available literature in order to define the range of nitrate/nitrite effects on animals. Though the literature deals primarily with livestock and experimental animals, much of the contemporary research is concerned with human nitrite intoxication. Thus, the effects on man are discussed where appropriate. Some of…

Deeb, Barbara S.; Sloan, Kenneth W.

322

A Proteomic Study of Protein Tyrosine Nitration  

E-print Network

from Sigma-Aldrich Chemical Company (St.Louis, MO), and was nitrated with peroxynitrite (ONOO-) synthesized in the laboratory according to Beckman et. al. (12). Tris/HCl, MgCl2 sodium phosphate diabasic (Na2HPO4), guanidine-HCl and sequencing grade...

Hong, Sung Jung

2008-08-28

323

Negative ion spectrometry for detecting nitrated explosives  

NASA Technical Reports Server (NTRS)

Ionization procedure is modified to produce mainly negative ions by electron capture. Peaks of negative ions are monitored conventionally. Nitrated organic materials could be identified directly from sample sniff inlet stream by suitably modified mass spectrometer because of unique electronegativity which nitro group imparts to organic material.

Boettger, H. G.; Yinon, J.

1975-01-01

324

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

325

Denitration of High Nitrate Salts Using Reductants  

SciTech Connect

This report describes work conducted by Pacific Northwest National Laboratory (PNNL), in conjunction with Idaho National Engineering and Environmental Laboratory (INEEL), to remove nitrates in simulated low-activity waste (LAW). The major objective of this work was to provide data for identifying and demonstrating a technically viable and cost-effective approach to condition LAW for immobilization (grout).

HD Smith; EO Jones; AJ Schmidt; AH Zacher; MD Brown; MR Elmore; SR Gano

1999-05-03

326

Review on Thermal Decomposition of Ammonium Nitrate  

Microsoft Academic Search

In this review data from the literature on thermal decomposition of ammonium nitrate (AN) and the effect of additives to their thermal decomposition are summarized. The effect of additives like oxides, cations, inorganic acids, organic compounds, phase-stablized CuO, etc., is discussed. The effect of an additive mainly occurs at the exothermic peak of pure AN in a temperature range of

Shalini Chaturvedi; Pragnesh N. Dave

2013-01-01

327

4-Meth­oxy­anilinium 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. PMID:22065633

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

2011-01-01

328

Ammonium nitrate: a promising rocket propellant oxidizer  

Microsoft Academic Search

Ammonium nitrate (AN) is extensively used in the area of fertilizers and explosives. It is present as the major component in most industrial explosives. Its use as an oxidizer in the area of propellants, however, is not as extensive as in explosive compositions or gas generators. With the growing demand for environmental friendly chlorine free propellants, many attempts have been

C. Oommen; S. R. Jain

1999-01-01

329

Electrochemical protection of zirconium in oxidizing hydrochloric acid solutions  

SciTech Connect

An electrochemical protection technique using cathodic polarization to maintain zirconium below its critical repassivation potential was used to avoid pitting and stress corrosion cracking (SCC) in hydrochloric acid (HCI) containing ferric ions (Fe/sup +3/). Corrosion and pit penetration rates are reported for pickled, abraded, and as-received surface conditions in 10, 20, and 37% HCI containing 50, 100, or 500 ppm Fe/sup +3/ at temperatures to boiling. The pickled surface was the least susceptible to pitting in the 64 day tests. Electrochemical protection is then evaluated for total immersion, partial immersion, U-bend, and constant strain rate tensile tests. Protection is effective in eliminating pitting and SCC in 10 and 20% HCI containing Fe/sup +3/.

Yuu, T-L.; Maguire, M.

1984-06-01

330

On the oxidation of Zirconium by heat tinting  

NASA Astrophysics Data System (ADS)

The early stages of the oxidation of iodide zirconium in the temperature range 673-823 K were studied using the heat tinting technique. An activation energy of 128 kJ/mol was calculated. Anisotropy of the oxidation is significant and depends on the preferred orientation of the grains. Twins have indicated the anisotropic nature of the oxidation process by showing different color contrasts. It was found that the increase in the thickness of the oxide film takes place by the nucleation and growth mechanism. This process was noted to be extremely dependent on the orientation of the grains. Preferential oxidation of the bulk of the grains was observed and substructure formation could be easily identified.

El-Shanshoury, I. A.; Chirkin, A. V.; El-Yazgi, A.

1987-06-01

331

Fabrication of NiO/zirconium oxide nanofibers by electrospinning.  

PubMed

The electrospinning technique has been used to fabricate 1D inorganic-organic composite nanofibers from solutions containing poly(vinyl alcohol) (PVA) and suitable aqueous precursors of nickel and zirconium ions. Upon calcination, nickel oxide/zirconia nanofibers retained the original morphological features of as-spun nanofibers. X-ray diffraction was used to identify the crystalline nature of the final product and analytical tools such as Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and atomic force microscopy (AFM) were employed to elucidate the pathway of ceramic phase formation and the systematic evolution of morphological features in the as-spun and calcined fibers. These fibers will find potential applications in biomedical field. PMID:25491841

Sundarrajan, Subramanian; Venkatesan, Arunachalam; Agarwal, Satya R; Ahamed, Nabeela Nasreen Shaik Anwar; Ramakrishna, Seeram

2014-12-01

332

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

333

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

334

Effect of yttrium on nucleation and growth of zirconium hydrides  

NASA Astrophysics Data System (ADS)

Addition of yttrium in zirconium causes precipitates of yttrium, which form two types of particles and are oxidized upon heat treatment. One type of particles with sub-micrometer scale sizes has a low population, whereas the other with nano scale sizes has a high population and cluster distribution. Owing to strong affinity of yttrium to hydrogen, the nanoparticles, mostly within the grains of the Zr-Y alloy, attract nucleation of hydrides at the clusters of the nanoparticles and cause preferential distribution of intragranular hydrides. In comparison with that of Zr, additional nanoparticles in the Zr-Y alloy impede further growth of hydride precipitates during hydriding. It is deduced that the impediment of growing hydride precipitates by the nanoparticles is developed during an auto-catalytic nucleation process, which leads to formation of thin and intragranular hydrides, favorable to mitigation of hydride embrittlement.

Li, Changji; Xiong, Liangyin; Wu, Erdong; Liu, Shi

2015-02-01

335

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

336

Electrochemical nitrate biosensor based on poly(pyrrole-viologen) film-nitrate reductase-clay composite.  

PubMed

The immobilization of nitrate reductase (NR) was performed by entrapment in a laponite clay gel and cross-linking by glutaraldehyde. In presence of nitrate and methyl viologen, a catalytic current appeared at -0.60 V illustrating the enzymatic reduction of nitrate into nitrite via the reduced form of the freely diffusing methyl viologen. The electropolymerization of a water-soluble pyrrole viologen derivative within the interlamellar spaces and channels of the host clay matrix successfully carried out the electrical wiring of the entrapped NR. Rotating disk measurements led to the determination of kinetic constants, namely k(2)=10.7 s(-1) and K(M)=7 microM. These parameters reflect the efficiency of the electro-enzymatic reduction of nitrate and the substrate affinity for the immobilized enzyme. PMID:18501683

Cosnier, S; Da Silva, S; Shan, D; Gorgy, K

2008-11-01

337

Fabrication and characterization of zirconium carbide (ZrC) nanofibers with thermal storage property  

Microsoft Academic Search

Zirconium carbide (ZrC) nanofibers were fabricated by the electrospinning method and subsequent heat-treatment. The solution for electrospinning was prepared by dissolving zirconium acetyl acetonate and cellulose acetate in glacial acetic acid and 2,4-pentanedione as common solvents. The effects of the solution properties used for electrospinning, including the concentrations of the starting materials, the C\\/Zr ratio of the solutions, and soaking

Young Sik Nam; Xue Mei Cui; Lim Jeong; Jae Yeol Lee; Won Ho Park

2009-01-01

338

Fabrication of zirconium carbide (ZrC) ultra-thin fibers by electrospinning  

Microsoft Academic Search

Zirconium carbide (ZrC) nanofibers were successfully fabricated by electrospinning and annealing. The electrospinning solution was prepared by dissolving zirconium acetyl acetonate, phenolic resins in a solvent mixture of ethyl alcohol and 2,4-pentanedione. Electrospinning was carried out successfully at a positive voltage of 26 kV, with a mass flow rate of 1.0 mL\\/h, and a working distance of 10 cm. The ZrC phase was

Xue Mei Cui; Young Sik Nam; Jae Yeol Lee; Won Ho Park

2008-01-01

339

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

340

A simple route for organic covalent grafting onto zirconium carbide particles  

NASA Astrophysics Data System (ADS)

Starting from core-shell zirconium carbide powders, a covalent grafting was described, using a direct nucleophilic substitution in diethyl ether. Thus, two different organic molecules were attached onto the surface of the ceramic, through Sisbnd Osbnd Zr and Csbnd Osbnd Zr bonds. The materials were characterized by means of TEM and XPS characterizations. These new systems could represent an original route to elaborate zirconium carbide-based hybrid materials.

Lucas, Romain; Pizon, David; Laborde, Etienne; Trolliard, Gilles; Foucaud, Sylvie; Maître, Alexandre

2013-12-01

341

Synthesis and characterization of novel aramid-zirconium oxide micro-composites  

Microsoft Academic Search

New micro-composites containing different proportions of zirconium oxide in aromatic polyamide have been prepared via a sol-gel process. Poly(phenyleneterephthalamide) chains with carbonyl chloride end groups were synthesized by reacting a mixture of p- and m-phenylene diamines with terephthaloyl chloride. The chain ends were endcapped with aminophenyltrimethoxysilane. Appropriate amount of zirconium propoxide solution (82.3 wt.%) in propanol was mixed in the

H. U. Rehman; M. I. Sarwar; Z. Ahmad; H. Krug; H. Schmidt

1997-01-01

342

X-Ray Diffraction Study of Shock-Induced Phase Transformations in Zirconium and Bismuth  

Microsoft Academic Search

Pulse X-ray patterns of polycrystalline zirconium and monocrystalline bismuth are obtained at the moment of shock-wave stimulation of samples. The exposure time of X-ray photography is 0.2–0.3 ms. Zirconium samples are investigated at shock pressures of 5, 9.5, 15, and 29 GPa. At P = 5 and 9.5 GPa, the structure of the initial a-phase is observed. At 15 and

A. M. Podurets; V. V. Dorokhin; R. F. Trunin

2003-01-01

343

Nitrated phenols in the atmosphere: a review  

NASA Astrophysics Data System (ADS)

This paper reviews the data concerning the atmospheric occurrence of nitrophenols, both in the gas and in the condensed phase (rainwater, cloud, fog and snow). Data obtained from field campaigns are reported, together with a description of the analytical techniques employed for the identification and quantification of nitrophenols. Analysis is usually performed using techniques such as High Performance Liquid Chromatography (HPLC) or Gas Chromatography-Mass Spectrometry (GC-MS), with the sampling method largely determined according to the matrix under investigation. The sources of atmospheric nitrophenols include direct emissions resulting from combustion processes, hydrolysis of pesticides (e.g. parathion) and the secondary formation of nitrophenols in the atmosphere. Atmospheric nitration of phenol can take place both in the gas and liquid phases, but the relative importance of these processes is still under discussion. The gas-phase nitration involves reaction between phenol and rad OH+ rad NO 2 during the day or rad NO 3+ rad NO 2 during the night. Gas-phase nitration during the day yields only 2-nitrophenol (2-NP); while during the night it is thought that both 2-NP and 4-nitrophenol (4-NP) may be formed. Because of many gaps in the experimental evidence it is apparent that more research is required to indicate whether the 4-NP present in the environment can be accounted for by this nighttime process. Nitration in the condensed phase can be initiated by electrophilic nitration agents such as N 2O 5 and ClNO 2. Other liquid-phase processes can also take place, in the presence of rad NO 3, nitrate and nitrite, in the dark and under irradiation. Condensed-phase processes have been shown to yield 2- and 4-NP in similar amounts. It is also important to consider the atmospheric sinks of nitrophenols. The rate constant for the reaction between 2-NP and rad OH in the gas phase is rather low (9.0×10 -13 cm 3 molecule -1 s -1), while incomplete data are available for the reaction with rad NO 3. In addition, condensed-phase processes might also represent an important nitrophenol sink. Potential loss routes include the reaction with radicals such as rad OH and rad NO 3 in aqueous solution as well as the nitration to form the dinitrophenols.

Harrison, Mark A. J.; Barra, Silvia; Borghesi, Daniele; Vione, Davide; Arsene, Cecilia; Iulian Olariu, Romeo

344

Ammonium repression of nitrate reductase formation in Lemna minor L  

Microsoft Academic Search

The presence of ammonium is shown to inhibit the nitrate-promoted formation of nitrate reductase in Lemna minor L. The ammonium inhibition does not result from an inhibition of nitrate accumulation. The kinetics of the ammonium inhibition suggest it is not a direct effect of ammonium. The inhibition could result from the build up of a product of ammonium assimilation or

T. O. Orebamjo; G. R. Stewart

1975-01-01

345

Ammonium inactivation of nitrate reductase in Lemna minor L  

Microsoft Academic Search

The addition of ammonium to nitrate induced plants of Lemna minor L. brings about a rapid loss in extractable nitrate reductase activity. This inactivation is reversible both in vivo and in vitro. Inhibitors of RNA and protein synthesis do not protect nitrate reductase against ammonium inactivation. It is suggested that factors, in addition to ammonium ions, are components of the

T. O. Orebamjo; G. R. Stewart

1975-01-01

346

NITRATE POLLUTION RISK ASSESSMENT: FROM THE MODEL TO THE INDICATOR  

E-print Network

study. INTRODUCTION Nitrate pollution is a threat to many of Europe's water resources, particularlyNITRATE POLLUTION RISK ASSESSMENT: FROM THE MODEL TO THE INDICATOR A. LACROIX 1 , F. LAURENT 2 , D. RUELLAND 3 , E. SAUBOUA 4 ABSTRACT The diffuse nature of nitrate pollution makes it difficult to evaluate

Paris-Sud XI, Université de

347

Evaporation of Ammonium Nitrate Aerosol in a Heated Nephelometer  

E-print Network

hygroscopic inorganic salts (i.e., ammonium sulfate, ammonium nitrate) which increase in size with increasingEvaporation of Ammonium Nitrate Aerosol in a Heated Nephelometer: Implications for Field National Laboratory, Upon, New York, 11973-5000 Ammonium nitrate is a semivolatile aerosol component under

348

Predicting Ground Water Nitrate Concentration from Land Use  

E-print Network

concentrations of nitrate in drinking water can cause low oxygen levels in the blood of infants, known of 10 mg/L nitrate. Increased nitrogen levels also detrimentally affect coastal waters by expeditingPredicting Ground Water Nitrate Concentration from Land Use by Kristin K. Gardner1 and Richard M

Vogel, Richard M.

349

Nitrate levels in shallow groundwater of upstate New York, USA  

Microsoft Academic Search

This paper summarizes research evaluating nitrate levels in shallow groundwater of upstate New York, USA. Water from abandoned dug wells in six different land-use categories was analyzed for nitrate. Findings indicate that regardless of overlying land-use, shallow groundwater is susceptible to high levels of nitrate. Over 60 percent of the water samples tested, including at least one sample from each

Glenn R. Harris; Brian D. Henry; Jeffrey S. Deyette

1996-01-01

350

Agronomy Facts 17 Presidedress Soil Nitrate Test for  

E-print Network

has shown that when the soil nitrate-N level is above 21 ppm, there is little chance of an economic response to adding additional N to the field. At soil nitrate- N levels below 21 ppm, sidedress NAgronomy Facts 17 Presidedress Soil Nitrate Test for Corn NitrogeN aNd CorN ProduCtioN Nitrogen (N

Kaye, Jason P.

351

EUROPEAN LARGE LAKES III Identification of factors constraining nitrate assimilation  

E-print Network

-long increase in nitrate levels (Sterner et al., 2007). This trend was initially reported in the years followingEUROPEAN LARGE LAKES III Identification of factors constraining nitrate assimilation in Lake Science+Business Media Dordrecht 2013 Abstract Despite a well-documented rise in nitrate concentration

Berges, John A.

352

Gas pressure in sealed sample cans concentrated plutonium nitrate  

Microsoft Academic Search

The objective of this work was to establish as fact that the predominant gas evolved from concentrated plutonium nitrate solutions is oxygen. Four sample cans containing plutonium nitrate at various concentrations were sealed using plug valves equipped with pressure gages. The results obtained showed that the gas evolved from concentrated plutonium nitrate solutions is predominately oxygen. It is believed that

1953-01-01

353

40 CFR 721.5769 - Mixture of nitrated alkylated phenols.  

Code of Federal Regulations, 2010 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...

2010-07-01

354

Disposable nitrate-selective optical sensor based on fluorescent dye  

Technology Transfer Automated Retrieval System (TEKTRAN)

A simple, disposable thin-film optical nitrate sensor was developed. The sensor was fabricated by applying a nitrate-selective polymer membrane on the surface of a thin polyester film. The membrane was composed of polyvinylchloride (PVC), plasticizer, fluorescent dye, and nitrate-selective ionophore...

355

THE CONTROL OF NITRATE AS A WATER POLLUTANT  

EPA Science Inventory

This study was based on the premise that the most logical approach to reducing nitrate leaching in soils was to limit the amount of nitrate in the soil solution at any one time. Methods of limiting the concentration of nitrate in the soil solution while maintaining an adequate su...

356

Original article A simple indicator for diagnosing nitrate leaching risk  

E-print Network

Original article A simple indicator for diagnosing nitrate leaching risk below the root zone using at three different sites for assessing nitrate leaching. The above measurements were made every 10 days 1996-1997. A nitrate leaching risk indicator was calculated by using the soil water potential gradient

Paris-Sud XI, Université de

357

The STICS model to predict nitrate leaching following agricultural practices  

E-print Network

The STICS model to predict nitrate leaching following agricultural practices Nathalie SCHNEBELENa-crop model STICS in order to predict the impact of agricultural practices on nitrate leaching on both plot existing within the studied area. The results indicate that N leaching and nitrate concentration

Paris-Sud XI, Université de

358

Zirconium Copper — a New Material for Use at Low Temperatures?  

NASA Astrophysics Data System (ADS)

Cryogenic instruments usually require components with high thermal conductivity. Pure (non alloyed) copper offers very high conductivity, but is soft and not thus always suitable structurally. High conductivity beryllium copper (BeCu) alloys are a common choice when copper is unsuitable since they offer a good compromise between hardness and thermal conductivity. These alloys contain a small (<1%) amount of beryllium (along with a few percent of nickel or cobalt), with strength being obtained by precipitation hardening. An alternative precipitation hardened copper alloy is C15000 zirconium copper (ZrCu), which contains < 0.2% zirconium with the remainder being copper. This material does not seem to be generally used in cryogenic systems, though hardness and strength are comparable to BeCu. Moreover, the lower impurity content suggests that the thermal conductivity should be higher than for BeCu. I present residual resistivity measurements suggesting that ZrCu does indeed possess considerably higher conductivity than BeCu (19 Wm-1K-1 at 1 K compared to approximately 2 Wm-1K-1), and should therefore be a very useful material. A method is given for extrapolating the low temperature thermal conductivity values to temperatures up to 300 K; good agreement is seen with room temperature data-sheet values. This extrapolation method is shown to also be applicable to BeCu and thus presumably other dilute copper alloys, and is used to give recommended values for coin silver and various BeCu alloy types, including C17510 and C17200.

Woodcraft, Adam L.

2006-09-01

359

Zirconium Copper - a New Material for Use at Low Temperatures?  

SciTech Connect

Cryogenic instruments usually require components with high thermal conductivity. Pure (non alloyed) copper offers very high conductivity, but is soft and not thus always suitable structurally. High conductivity beryllium copper (BeCu) alloys are a common choice when copper is unsuitable since they offer a good compromise between hardness and thermal conductivity. These alloys contain a small (<1%) amount of beryllium (along with a few percent of nickel or cobalt), with strength being obtained by precipitation hardening. An alternative precipitation hardened copper alloy is C15000 zirconium copper (ZrCu), which contains < 0.2% zirconium with the remainder being copper. This material does not seem to be generally used in cryogenic systems, though hardness and strength are comparable to BeCu. Moreover, the lower impurity content suggests that the thermal conductivity should be higher than for BeCu. I present residual resistivity measurements suggesting that ZrCu does indeed possess considerably higher conductivity than BeCu (19 Wm-1K-1 at 1 K compared to approximately 2 Wm-1K-1), and should therefore be a very useful material. A method is given for extrapolating the low temperature thermal conductivity values to temperatures up to 300 K; good agreement is seen with room temperature data-sheet values. This extrapolation method is shown to also be applicable to BeCu and thus presumably other dilute copper alloys, and is used to give recommended values for coin silver and various BeCu alloy types, including C17510 and C17200.

Woodcraft, Adam L. [School of Physics and Astronomy, Cardiff University, Cardiff, 5 The Parade, Cardiff, CF24 3YB (United Kingdom)

2006-09-07

360

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

361

Graded selective coatings based on zirconium and titanium oxynitride  

NASA Astrophysics Data System (ADS)

The aim of this study was the development and characterization of transition metal oxynitride multilayers for optical applications. The reactive RF magnetron sputtering technique in rotation mode was used for stacking of zirconium oxynitride (ZrNO) and titanium oxynitride (TiNO) nanolayers. The depositions were carried out in a reactive Ar+N2+O2 atmosphere by sputtering titanium and zirconium targets. By means of different substrate rotation speeds, the bilayer period has been changed in the range 11-20 nm. A multilayer deposition rate increasing with the bilayer period decreasing has been evaluated. Structural, compositional, mechanical and optical analyses have been performed. The x-ray diffraction spectra confirmed the formation of a multilayer structure with a nitride formation prevalence. Non-abrupt interfaces between the layers and non-uniform chemical composition (chemical intermixing) have been detected by transmission electron microscope (TEM) observations. The gradient interface structure turns out to be an advantage for the improvement of the mechanical properties. Higher hardness values were calculated by the Chicot-Lesage and Jonsson-Hogmark models for TiNO/ZrNO multilayer compared with monolayer TiNO and ZrNO coatings. Also SIMS analysis has confirmed a compositional interface grading but also an increase in oxygen content with decreasing substrate rotation speed or similarly with decreasing deposition rate. Moreover, a tuning of the optical properties, going from metallic behaviour to dielectric with the decrease in the substrate rotation speed has been gained. The variation of the deposition rate allows a sort of 'regulation' of the oxygen incorporation with a precise tailoring of the optical properties. This result can be employed with the aim of depositing graded composition multilayer systems with a precise control of their optical selective wavelength properties. The improvement in the mechanical performance in graded oxynitride multilayer coatings would also allow an increase in the optical device lifetime.

Rizzo, A.; Signore, M. A.; Tapfer, L.; Piscopiello, E.; Cappello, A.; Bemporad, E.; Sebastiani, M.

2009-06-01

362

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

363

Selective Nitrate Binding in Competitive Hydrogen Bonding Solvents: Do Anion–? Interactions Facilitate Nitrate Selectivity?**  

PubMed Central

New tripodal urea receptors demonstrate preferential binding of anions over competitive hydrogen bonding solvents. 1H NMR titrations in 10% DMSO-d6/CDCl3 show a higher affinity for nitrate over the halides for the fluorinated receptor, which is lost when the fluorines are removed. An “anion–?” interaction between the nitrate and the ?-system of the ethynyl-substituted arene is proposed as the source of this selectivity. PMID:23939999

Watt, Michelle M.; Zakharov, Lev N.

2013-01-01

364

Solubility of uranyl nitrate in nitric acid solutions of aluminum nitrate  

SciTech Connect

The solubility of uranyl nitrate in nitric acid solutions of aluminum nitrate at 25/sup 0/C containing 10, 20 and 30 mass % of nitric acid has been studied by the isothermal method. The Schreinemakers method has been used to establish the composition of the solid phases, which has been confirmed by crystallographic and thermographic studies. Data are presented on the viscosity and density of saturated solutions.

Medkov, B.K.; Petrov, M.R.; Roslyakova, O.N.

1988-11-01

365

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. PMID:16347078

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

1986-01-01

366

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

367

Surface-enhanced nitrate photolysis on ice.  

PubMed

Heterogeneous nitrate photolysis is the trigger for many chemical processes occurring in the polar boundary layer and is widely believed to occur in a quasi-liquid layer (QLL) at the surface of ice. The dipole-forbidden character of the electronic transition relevant to boundary layer atmospheric chemistry and the small photolysis/photoproduct yields in ice (and in water) may confer a significant enhancement and interfacial specificity to this important photochemical reaction at the surface of ice. Using amorphous solid water films at cryogenic temperatures as models for the disordered interstitial air-ice interface within the snowpack suppresses the diffusive uptake kinetics, thereby prolonging the residence time of nitrate anions at the surface of ice. This approach allows their slow heterogeneous photolysis kinetics to be studied, providing the first direct evidence that nitrates adsorbed onto the first molecular layer at the surface of ice are photolyzed more effectively than those dissolved within the bulk. Vibrational spectroscopy allows the ?3-fold enhancement in photolysis rates to be correlated with the nitrates' distorted intramolecular geometry, thereby hinting at the role played by the greater chemical heterogeneity in their solvation environment at the surface of ice than that in the bulk. A simple 1D kinetic model suggests (1) that a 3(6)-fold enhancement in photolysis rate for nitrates adsorbed onto the ice surface could increase the photochemical NO2 emissions from a 5(8) nm thick photochemically active interfacial layer by 30(60)%, and (2) that 25(40)% of the NO2 photochemical emissions to the snowpack interstitial air are released from the topmost molecularly thin surface layer on ice. These findings may provide a new paradigm for heterogeneous (photo)chemistry at temperatures below those required for a QLL to form at the ice surface. PMID:25671500

Marcotte, Guillaume; Marchand, Patrick; Pronovost, Stéphanie; Ayotte, Patrick; Laffon, Carine; Parent, Philippe

2015-03-12

368

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

369

The impact of zirconium oxide radiopacifier on the early hydration behaviour of white Portland cement.  

PubMed

Zirconium oxide has been identified as a candidate radiopacifying agent for use in Portland cement-based biomaterials. During this study, the impact of 20 wt.% zirconium oxide on the hydration and setting reactions of white Portland cement (WPC) was monitored by powder X-ray diffraction (XRD), (29)Si and (27)Al magic angle spinning nuclear magnetic resonance spectroscopy (MAS NMR), transmission electron microscopy (TEM) and Vicat apparatus. The presence of 20 wt.% zirconium oxide particles in the size-range of 0.2 to 5 ?m was found to reduce the initial and final setting times of WPC from 172 to 147 min and 213 to 191 min, respectively. Zirconium oxide did not formally participate in the chemical reactions of the hydrating cement; however, the surface of the zirconium oxide particles presented heterogeneous nucleation sites for the precipitation and growth of the early C-S-H gel products which accelerated the initial setting reactions. The presence of zirconium oxide was found to have little impact on the development of the calcium (sulpho)aluminate hydrate phases. PMID:25428091

Coleman, Nichola J; Li, Qiu

2013-01-01

370

Extraction of nitric acid, uranyl nitrate, and bismuth nitrate from aqueous nitric acid solutions with CMPO  

SciTech Connect

DOE sponsored development of the transuranium extraction (TRUEX) process for removing actinides from radioactive wastes. The solvent is a mixture of CMPO and TBP. Since the extraction characteristics of CMPO are not as well understood as those of TBP, the extraction of nitric acid, uranyl nitrate, and bismuth nitrate with CMPO (dissolved in n-dodecane) were studied. Results indicate that CMPO extracts nitric acid with a 1:1 stoichiometry; equilibrium constant is 2. 660{plus_minus}0.092 at 25 C, and extraction enthalpy is -5. 46{plus_minus}0.46 kcal/mol. Slope analysis indicates that uranyl nitrate extracts with a mixed equilibria of 1:1 and 2:1 stoichiometries in nearly equal proportion. Equil. constant of the 2: 1 extraction was 1.213 {times} 10{sup 6}{plus_minus}3.56 {times} 10{sup 4} at 25 C; reaction enthalpy was -9.610{plus_minus}0.594 kcal/mol. Nitration complexation constant is 8.412{plus_minus}0.579, with an enthalpy of -10.72{plus_minus}1.87 kcal/mol. Bismuth nitrate also extracts with a mixed equilibria of (perhaps) 1:1 and 2:1 stoichiometries. A 2:1 extraction equilibrium and a nitrate complexation adequately model the data. Kinetics and enthalpies were also measured.

Spencer, B.B.

1995-08-01

371

Preparation and characterization of three-dimensional carbon fiber reinforced zirconium carbide composite by precursor infiltration and pyrolysis process  

Microsoft Academic Search

Three-dimensional carbon fiber reinforced zirconium carbide composite (3D C\\/ZrC) was fabricated for ultra high temperature applications by precursor infiltration and pyrolysis (PIP) process using the mixture of zirconium butoxide (Zr(OC4H9)4) and divinylbenzene (DVB) as precursor of zirconium carbide. The micro-structural, mechanical and ablative properties of the 3D C\\/ZrC composite were studied. The flexural strength of the composite was 107.6MPa, the

Dan Zhao; Changrui Zhang; Haifeng Hu; Yudi Zhang

2011-01-01

372

Does the evidence about health risks associated with nitrate ingestion warrant an increase of the nitrate standard for drinking water?  

Microsoft Academic Search

Several authors have suggested that it is safe to raise the health standard for nitrate in drinking water, and save money on measures associated with nitrate pollution of drinking water resources. The major argument has been that the epidemiologic evidence for acute and chronic health effects related to drinking water nitrate at concentrations near the health standard is inconclusive. With

Hans JM van Grinsven; Mary H Ward; Nigel Benjamin; Theo M de Kok

2006-01-01

373

Seasonal variations in nitrate content, total nitrogen, and nitrate reductase activities of macrophytes from a chalk stream in Upper Bavaria  

Microsoft Academic Search

11 macrophytic species from a groundwater influenced chalk stream in Upper Bavaria were investigated during a period of one year in order to determine differences in the endogenous nitrate content, in total nitrogen content and in nitrate reductase activity (NRA). Nitrate concentrations of different plants taken from the same site of the river varied by a factor of approximately 103.

A. Melzer; R. Kaiser

1986-01-01

374

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. PMID:24795702

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

375

Preparation of zirconium oxy ion-imprinted particle for the selective separation of trace zirconium ion from water.  

PubMed

Zr(IV) oxy ion-imprinted particle (Zr-IIP) was prepared using the metal ion imprinting technique in a sol-gel process on the surface of amino-silica. The dosages of zirconium ions as imprinted target, (3-aminopropyl) triethoxysilane (APTES) as a functional monomer and teraethyl orthosilicate (TEOS) as a cross-linker were optimized. The prepared Zr-IIP and Zr(IV) oxy ion non-imprinted particle (Zr-NIP) were characterized. pH effect, binding ability and the selectivity were investigated in detail. The results showed that the Zr-IIP had an excellent binding capacity and selectivity in the water. The equilibrium data fitted well to the pseudo-second-order kinetic and the Langmuir model for Zr(IV) binding onto Zr-IIP, respectively. The saturate binding capacity of Zr-IIP was found to be 196.08 ?mol g(-1), which was 18 times higher than that of Zr-NIP. The sequence of binding efficiency of Zr-IIP for various ions was Zr(IV)>Cu(II)>Sb(III)>Eu(III). The coordination number has an important effect on the dimensional binding capacity. The equilibrium binding capacity of Zr-IIP for Zr(IV) decreased little under various concentrations of Pb(II) ions. The analysis of relative selectivity coefficient (Kr) indicated that the Zr-IIP had an appreciable binding specificity towards Zr(IV) although the competitive ions coexisted in the water. The Zr-IIP could serve as an efficient selective material for recovering or removing zirconium from the water environment. PMID:25004058

Ren, Yueming; Liu, Pingxin; Liu, Xiaoli; Feng, Jing; Fan, Zhuangjun; Luan, Tianzhu

2014-10-01

376

Addressing Nitrate in California's Drinking Water Report for the State Water Resources Control Board Report to the Legislature  

E-print Network

Groundwater Regulatory and Funding Options for Nitrate Groundwater Contamination TECHNICAL REPORT 8: #12;Regulatory and Funding Options for Nitrate Groundwater Contamination Technical Report 8 Addressing Nitrate for Nitrate Groundwater Contamination. Technical Report 8 in Addressing Nitrate in California's Drinking Water

Pasternack, Gregory B.

377

Differential pulse polarographic determination of nitrate in environmental materials.  

PubMed

Nitrate can be determined with reliable accuracy and sensitivity by differential pulse polarography utilizing the catalytic reaction between nitrate and uranyl ion in the presence of potassium sulphate. The differential pulse polarographic peak-height is proportional to nitrate concentration from 1 to 50 muM. The calculated detection limit for nitrate is 8 x 10(-7)M in pure aqueous solution. The method has been applied to determination of nitrate in fresh snow, and river waters and animal feeds. PMID:18963604

Hemmi, H; Hasebe, K; Ohzeki, K; Kambara, T

1984-05-01

378

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). PMID:21172423

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

2010-01-01

379

Seasonal nitrate algorithms for nitrate retrieval using OCEANSAT-2 and MODIS-AQUA satellite data.  

PubMed

In situ datasets of nitrate, sea surface temperature (SST), and chlorophyll a (chl a) collected during the monthly coastal samplings and organized cruises along the Tamilnadu and Andhra Pradesh coast between 2009 and 2013 were used to develop seasonal nitrate algorithms. The nitrate algorithms have been built up based on the three-dimensional regressions between SST, chl a, and nitrate in situ data using linear, Gaussian, Lorentzian, and paraboloid function fittings. Among these four functions, paraboloid was found to be better with the highest co-efficient of determination (postmonsoon: R (2)?=?0.711, n?=?357; summer: R (2)?=?0.635, n?=?302; premonsoon: R (2)?=?0.829, n?=?249; and monsoon: R (2)?=?0.692, n?=?272) for all seasons. Based on these fittings, seasonal nitrate images were generated using the concurrent satellite data of SST from Moderate Resolution Imaging Spectroradiometer (MODIS) and chlorophyll (chl) from Ocean Color Monitor (OCM-2) and MODIS. The best retrieval of modeled nitrate (R (2)?=?0.527, root mean square error (RMSE)?=?3.72, and mean normalized bias (MNB)?=?0.821) was observed for the postmonsoon season due to the better retrieval of both SST MODIS (28 February 2012, R (2)?=?0.651, RMSE?=?2.037, and MNB?=?0.068) and chl OCM-2 (R (2)?=?0.534, RMSE?=?0.317, and MNB?=?0.27). Present results confirm that the chl OCM-2 and SST MODIS retrieve nitrate well than the MODIS-derived chl and SST largely due to the better retrieval of chl by OCM-2 than MODIS. PMID:25762424

Durairaj, Poornima; Sarangi, Ranjit Kumar; Ramalingam, Shanthi; Thirunavukarassu, Thangaradjou; Chauhan, Prakash

2015-04-01

380

Nitrate release by Caribbean reef sponges  

Microsoft Academic Search

Two coral reef sponges were examined in situ off Puerto Rico for fluxes of dissolved inorganic nitrogen. Chondrilla nucula, a ubiquitous Caribbean sponge with cyanobacterial symbionts, releases large amounts of nitrate (600 nmol N g I (dry wt) h-l; 4,000 Mmol N me2 h-l). Since C. nucula covers a mean of 12% of the substratum, it potentially contributes between 50

JORGE E. CORREDOR; CLIVE R. WILKINSON; VANCE P. VICENTE; JULIO M. MORELL; ERNESTO OTERO

1988-01-01

381

Nitrate in groundwater in the United States  

Microsoft Academic Search

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

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

2009-01-01

382

Temperature programmed decomposition of uranyl nitrate hexahydrate  

Microsoft Academic Search

Temperature programmed decomposition (TPD) of uranyl nitrate hexahydrate has been studied using evolved gas analysis mass spectrometry (EGA-MS) in the temperature range 300–1400 K. Thermogravimetric (TGA) investigations were performed in the temperature range 300–1100 K. An attempt has been made to resolve the complexity of decomposition behaviour through suitable comparison of TGA and EGA-MS data. Kinetic control regimes for various

S. Dash; M. Kamruddin; Santanu Bera; P. K. Ajikumar; A. K. Tyagi; S. V. Narasimhan; Baldev Raj

1999-01-01

383

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

384

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

385

Myeloperoxidase produces nitrating oxidants in vivo  

PubMed Central

Despite intense interest in pathways that generate reactive nitrogen species, the physiologically relevant mechanisms for inflammatory tissue injury remain poorly understood. One possible mediator is myeloperoxidase, a major constituent of neutrophils, monocytes, and some populations of macrophages. The enzyme uses hydrogen peroxide and nitrite to generate 3-nitrotyrosine in vitro. To determine whether myeloperoxidase produces nitrating intermediates in vivo, we used isotope dilution gas chromatography/mass spectrometry to quantify 3-nitrotyrosine in two models of peritoneal inflammation: mice infected with Klebsiella pneumoniae and mice subjected to cecal ligation and puncture. Both models developed an intense neutrophil inflammatory response, and the inflammatory fluid contained markedly elevated levels of 3-chlorotyrosine, a marker of myeloperoxidase action. In striking contrast, 3-nitrotyrosine levels rose only in the mice infected with K. pneumoniae. Levels of total nitrite and nitrate were 20-fold higher in mice injected with K. pneumoniae than in mice subjected to cecal ligation and puncture. Levels of 3-nitrotyrosine failed to increase in mice infected with K. pneumoniae that lacked functional myeloperoxidase. Our observations provide strong evidence that myeloperoxidase generates reactive nitrogen species in vivo and that it operates in this fashion only when nitrite and nitrate become available. PMID:12021246

Gaut, Joseph P.; Byun, Jaeman; Tran, Hung D.; Lauber, Wendy M.; Carroll, James A.; Hotchkiss, Richard S.; Belaaouaj, Abderrazzaq; Heinecke, Jay W.

2002-01-01

386

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

387

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

388

Cold-surface photochemistry of selected organic nitrates.  

PubMed

Reflection-absorption infrared (RAIR) spectroscopy has been used to explore the low temperature condensed-phase photochemistry of atmospherically relevant organic nitrates for the first time. Three alkyl nitrates, methyl, isopropyl, and isobutyl nitrate together with a peroxyacyl nitrate, peroxyacetyl nitrate (PAN), were examined. For the alkyl nitrates, similar photolysis products were observed whether they were deposited neat to the gold substrate or codeposited with water. In addition to peaks associated with the formation of an aldehyde/ketone and NO, a peak near 2230 cm(-1) was found to emerge in the RAIR spectra upon UV photolysis of the thin films. Together with evidence obtained by thermal programmed desorption (TPD), the peak is attributed to the formation of nitrous oxide, N2O, generated as a product during the photolysis. On the basis of the known gas-phase photochemistry for the alkyl nitrates, an intermediate pathway involving the formation of nitroxyl (HNO) is proposed to lead to the observed N2O photoproduct. For peroxyacetyl nitrate, CO2 was observed as a predominant product upon photolytic decomposition. In addition, RAIR absorptions attributable to the formation of methyl nitrate were also found to appear upon photolysis. By analogy to the known gas-phase and matrix-isolated-phase photochemistry of PAN, the formation of methyl nitrate is shown to likely result from the combination of alkoxy radicals and nitrogen dioxide generated inside the thin films during photolysis. PMID:25232898

O'Sullivan, Daniel; McLaughlin, Ryan P; Clemitshaw, Kevin C; Sodeau, John R

2014-10-23

389

A survey of dietary nitrate in well-water users.  

PubMed

The hypothesis that high nitrate ingestion may increase the risk of stomach cancer has led to concern over rising levels of nitrate in drinking water, but with little consideration as to whether nitrate from water makes a major contribution to total nitrate intake. In order to investigate the relative importance of water and food as sources of nitrate, 404 adult well-water users completed a diet diary over a 48-hour period and provided a 24-hour urine specimen and a sample of their drinking water. Where the waterborne nitrate level is less than 50 mg/I, as recommended by the World Health Organization (WHO), 30% of ingested nitrate is from water. As the well-water nitrate concentration rises the contribution of water to daily intake increases; at levels between 50 and 100 mg/I, on average, nearly 70% of daily intake is from water, and above 100 mg/I over 80% of daily intake is waterborne. Thus it is only at levels above those currently recommended by the WHO that waterborne nitrate appears to be the major contributor to total nitrate intake. PMID:6490303

Chilvers, C; Inskip, H; Caygill, C; Bartholomew, B; Fraser, P; Hill, M

1984-09-01

390

Growing patterns to produce 'nitrate-free' lettuce (Lactuca sativa).  

PubMed

Vegetables can contain significant amounts of nitrate and, therefore, may pose health hazards to consumers by exceeding the accepted daily intake for nitrate. Different hydroponic growing patterns were examined in this work in order to obtain 'nitrate-free lettuces'. Growing lettuces on low nitrate content nutrient solution resulted in a significant decrease in lettuces' nitrate concentrations (1741 versus 39 mg kg(-1)), however the beneficial effect was cancelled out by an increase in the ambient temperature. Nitrate replacement with ammonium was associated with an important decrease of the lettuces' nitrate concentration (from 1896 to 14 mg kg(-1)) and survival rate. An economically feasible method to reduce nitrate concentrations was the removal of all inorganic nitrogen from the nutrient solution before the exponential growth phase. This method led to lettuces almost devoid of nitrate (10 mg kg(-1)). The dried mass and calcinated mass of lettuces, used as markers of lettuces' quality, were not influenced by this treatment, but a small reduction (18%, p < 0.05) in the fresh mass was recorded. The concentrations of nitrite in the lettuces and their modifications are also discussed in the paper. It is possible to obtain 'nitrate-free' lettuces in an economically feasible way. PMID:25345876

Croitoru, Mircea Dumitru; Muntean, Daniela-Lucia; Fülöp, Ibolya; Modroiu, Adriana

2015-01-01

391

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. PMID:15682502

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

2005-01-01

392

Nitrate ammonification in mangrove soils: a hidden source of nitrite?  

PubMed Central

Nitrate reduction is considered to be a minor microbial pathway in the oxidation of mangrove-derived organic matter due to a limited supply of nitrate in mangrove soils. At a limited availability of this electron acceptor compared to the supply of degradable carbon, nitrate ammonification is thought to be the preferential pathway of nitrate reduction. Mangrove forest mutually differ in their productivity, which may lead to different available carbon to nitrate ratios in their soil. Hence, nitrate ammonification is expected to be of more importance in high- compared to low-productive forests. The hypothesis was tested in flow-through reactors that contain undisturbed mangrove soils from high-productive Avicennia germinans and Rhizophora mangle forests in Florida and low-productive Avicennia marina forests in Saudi Arabia. Nitrate was undetectable in the soils from both regions. It was assumed that a legacy of nitrate ammonification would be reflected by a higher ammonium production from these soils upon the addition of nitrate. Unexpectedly, the soils from the low-productive forests in Saudi Arabia produced considerably more ammonium than the soils from the high-productive forests in Florida. Hence, other environmental factors than productivity must govern the selection of nitrate ammonification or denitrification. A rather intriguing observation was the 1:1 production of nitrite and ammonium during the consumption of nitrate, more or less independent from sampling region, location, sampling depth, mangrove species and from the absence or presence of additional degradable carbon. This 1:1 ratio points to a coupled production of ammonium and nitrite by one group of nitrate-reducing microorganisms. Such a production of nitrite will be hidden by the presence of active nitrite-reducing microorganisms under the nitrate-limited conditions of most mangrove forest soils. PMID:25784903

Balk, Melike; Laverman, Anniet M.; Keuskamp, Joost A.; Laanbroek, Hendrikus J.

2015-01-01

393

The Fate of Nitrate in Intertidal Permeable Sediments  

PubMed Central

Coastal zones act as a sink for riverine and atmospheric nitrogen inputs and thereby buffer the open ocean from the effects of anthropogenic activity. Recently, microbial activity in sandy permeable sediments has been identified as a dominant source of N-loss in coastal zones, namely through denitrification. Some of the highest coastal denitrification rates measured so far occur within the intertidal permeable sediments of the eutrophied Wadden Sea. Still, denitrification alone can often account for only half of the substantial nitrate (NO3?) consumption. Therefore, to investigate alternative NO3? sinks such as dissimilatory nitrate reduction to ammonium (DNRA), intracellular nitrate storage by eukaryotes and isotope equilibration effects we carried out 15NO3? amendment experiments. By considering all of these sinks in combination, we could quantify the fate of the 15NO3? added to the sediment. Denitrification was the dominant nitrate sink (50–75%), while DNRA, which recycles N to the environment accounted for 10–20% of NO3? consumption. Intriguingly, we also observed that between 20 and 40% of 15NO3? added to the incubations entered an intracellular pool of NO3? and was subsequently respired when nitrate became limiting. Eukaryotes were responsible for a large proportion of intracellular nitrate storage, and it could be shown through inhibition experiments that at least a third of the stored nitrate was subsequently also respired by eukaryotes. The environmental significance of the intracellular nitrate pool was confirmed by in situ measurements which revealed that intracellular storage can accumulate nitrate at concentrations six fold higher than the surrounding porewater. This intracellular pool is so far not considered when modeling N-loss from intertidal permeable sediments; however it can act as a reservoir for nitrate during low tide. Consequently, nitrate respiration supported by intracellular nitrate storage can add an additional 20% to previous nitrate reduction estimates in intertidal sediments, further increasing their contribution to N-loss. PMID:25127459

Marchant, Hannah K.; Lavik, Gaute; Holtappels, Moritz; Kuypers, Marcel M. M.

2014-01-01

394

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

395

Zirconium phosphate waste forms for low-temperature stabilization of cesium-137-containing waste streams  

SciTech Connect

Novel chemically bonded phosphate ceramics are being developed and fabricated for low-temperature stabilization and solidification of waste streams that are not amenable to conventional high-temperature stabilization processes because volatiles are present in the wastes. A composite of zirconium-magnesium phosphate has been developed and shown to stabilize ash waste contaminated with a radioactive surrogate of {sup 137}Cs. Excellent retainment of cesium in the phosphate matrix system was observed in Toxicity Characteristic Leaching Procedure tests. This was attributed to the capture of cesium in the layered zirconium phosphate structure by intercalation ion-exchange reaction. But because zirconium phosphate has low strength, a novel zirconium/magnesium phosphate composite waste form system was developed. The performance of these final waste forms, as indicated by compression strength and durability in aqueous environments, satisfy the regulatory criteria. Test results indicate that zirconium-magnesium-phosphate-based final waste forms present a viable technology for treatment and solidification of cesium-contaminated wastes.

Singh, D.; Wagh, A.S.; Tlustochowicz

1996-04-01

396

Zirconium-based alloys, nuclear fuel rods and nuclear reactors including such alloys, and related methods  

DOEpatents

Zirconium-based metal alloy compositions comprise zirconium, a first additive in which the permeability of hydrogen decreases with increasing temperatures at least over a temperature range extending from 350.degree. C. to 750.degree. C., and a second additive having a solubility in zirconium over the temperature range extending from 350.degree. C. to 750.degree. C. At least one of a solubility of the first additive in the second additive over the temperature range extending from 350.degree. C. to 750.degree. C. and a solubility of the second additive in the first additive over the temperature range extending from 350.degree. C. to 750.degree. C. is higher than the solubility of the second additive in zirconium over the temperature range extending from 350.degree. C. to 750.degree. C. Nuclear fuel rods include a cladding material comprising such metal alloy compositions, and nuclear reactors include such fuel rods. Methods are used to fabricate such zirconium-based metal alloy compositions.

Mariani, Robert Dominick

2014-09-09

397

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

398

Characterization of zirconium thin films deposited by pulsed laser deposition  

NASA Astrophysics Data System (ADS)

Zirconium (Zr) thin films deposited on Si (100) by pulsed laser deposition (PLD) at different pulse repetition rates are investigated. The deposited Zr films exhibit a polycrystalline structure, and the X-ray diffraction (XRD) patterns of the films show the ? Zr phase. Due to the morphology variation of the target and the laser—plasma interaction, the deposition rate significantly decreases from 0.0431 Å/pulse at 2 Hz to 0.0189 Å/pulse at 20 Hz. The presence of droplets on the surface of the deposited film, which is one of the main disadvantages of the PLD, is observed at various pulse repetition rates. Statistical results show that the dimension and the density of the droplets increase with an increasing pulse repetition rate. We find that the source of droplets is the liquid layer formed under the target surface. The dense nanoparticles covered on the film surface are observed through atomic force microscopy (AFM). The root mean square (RMS) roughness caused by valleys and islands on the film surface initially increases and then decreases with the increasing pulse repetition rate. The results of our investigation will be useful to optimize the synthesis conditions of the Zr films.

Liu, Wei; Wan, Jing-Ping; Cai, Wu-Peng; Liang, Jian-Hua; Zhou, Xiao-Song; Long, Xing-Gui

2014-09-01

399

Improved Yttrium and Zirconium Abundances in Metal-Poor Stars  

NASA Astrophysics Data System (ADS)

Abstract We present new abundances of the lighter n-capture elements, Yttrium (Z=39) and Zirconium (Z=40) in the very metal poor, r-process rich stars BD+17 3248 and HD 221170. Very accurate abundances were obtained by use of the new transition probabilities for Y II published by Biémont et al. 2011, and Zr II by Malcheva et al. 2006, and by expanding the number of transitions employed for each element. For example, in BD+17 3248, we find log ???????=-0.03 +/- 0.03 (?????=0.15, from 23 lines) for Y II. As for Zr II, log ??????? = 0.65 +/- 0.03 (????? = 0.1, from 13 lines). The resulting abundance ratio is log ??????? [Y/Zr] = -0.68 +/- 0.05. The results for HD 221170 are in accord with those of BD+17 3248. The quantity of lines used to form the abundance means has increased significantly since the original studies of these stars, resulting in more trustworthy abundances. These observed abundance ratios are in agreement with an r-process-only value predicted from stellar models, but is under-abundant compared to an empirical model derived from direct analyses of meteoritic material. This ambiguity should stimulate further nucleosynthetic analysis to explain this abundance ratio. We would like to extend our gratitude to NSF grant AST-0908978 and the University of Texas Astronomy Department Rex G. Baker, Jr. Endowment for their financial support in this project.

Violante, Renata; Biemont, E.; Cowan, J. J.; Sneden, C.

2012-01-01

400

Zirconium umbelliferonephosphate - A luminescent organic-inorganic hybrid nanomaterial  

NASA Astrophysics Data System (ADS)

Zirconium umbelliferonephosphate (ZrO(UFP)) is prepared by nucleation in the ionic liquid [MeBu 3N][NTf 2]. According to electron microscopy the resulting nanoparticles exhibit mean particle diameters of about 50 nm. The organic-inorganic hybrid material ZrO(UFP) shows blue emission upon UV-excitation. Luminescence originates from the organic dye and is highly intense due to the molar amount of luminescent centers per nanoparticle. The as-prepared material turns out to be non-crystalline. Therefore, its chemical composition is validated by infrared spectroscopy, thermogravimetry, energy-dispersive X-ray analysis and elemental analysis. The results (i.e., thermal decomposition, Zr:P ratio, C-/H-concentration) are in accordance to the composition of ZrO(UFP). Upon addition of acid phosphatase the luminescence intensity of ZrO(UFP) is significantly increased due to enzymatic hydrolysis accompanied by a release of non-bound umbelliferone. Both aspects - the increase in luminescence intensity as well as the release of umbelliferone - might be of future interest regarding biomedical application of ZrO(UFP) nanoparticles.

Roming, Marcus; Feldmann, Claus

2011-03-01

401

Characterization of precipitates in a niobium-zirconium-carbon alloy  

NASA Technical Reports Server (NTRS)

A niobium alloy with 1 percent zirconium and 0.063 percent carbon by weight was investigated in the as-rolled and annealed conditions, and after high-temperature (1350 and 1400 K) exposure with and without an applied stress. In the as-rolled and annealed conditions, large metastable carbides were observed in addition to a regular distribution of small particles. During the high-temperature exposure, the majority of the large carbides were dissolved and a more stable carbide phase formed. This finely dispersed phase had a composition determined to be approximately 70 percent ZrC and approximately 30 percent NbC and showed some evidence of an orientation relationship with the matrix. The precipitates appeared to coarsen slightly after approximately 5000 hr exposure in the presence of an applied stress resulted in a decrease in the size and in the interparticle spacing of the stable precipitates. However, the composition of the precipitate phase and its ability to pin dislocations were not affected by the temperature or stress conditions.

Grobstein, T. L.; Titran, R. H.

1986-01-01

402

Fracture Resistance of a Zirconium Alloy with Reoriented Hydrides  

NASA Astrophysics Data System (ADS)

Zirconium alloy cladding materials typically contain circumferential hydrides that may be reoriented to align along the radial direction when the cladding tubes are heated above and then cooled below the solvus temperature. The objectives of this study were to investigate the critical stress levels required to cause hydride reorientation (HRT) and to characterize the fracture resistance of Zircaloy-2 after hydride reorientation. HRT heat-treatment was performed on hydrogen-charged Zircaloy-2 specimens at 593 K (320 °C) or 623 K (350 °C) for 1 to 2 hours, followed by cooling to 473 K (200 °C). Fracture testing was conducted on hydride-reoriented three-point bend specimens at 473 K (200 °C) using an in situ loading stage inside a scanning electron microscope. Direct observations indicated that the reoriented hydrides, which ranged from ?1 to 22 ?m in lengths, were more prone to fracture at larger sizes (>10 ?m) compared to smaller sizes (<0.5 ?m). The reoriented hydrides reduced fracture resistance through a void nucleation, growth, and coalescence process at the crack tip. The resulting crack-resistance curves for Zircaloy-2 with reoriented hydrides decrease from 38 to 21 MPa(m)1/2 with increasing hydrogen contents from 51 to 1265 wt ppm hydrogen.

Chan, Kwai S.; He, Xihua; Pan, Yi-Ming

2015-01-01

403

The effect of zirconium implantation on the structure of sapphire  

SciTech Connect

The effect of zirconium implantation on the structure of sapphire was investigated by 175 keV Zr implantation at room temperature to a fluence of 4 1016 ions/cm2 into sapphire single crystals. Samples were examined by several experimental techniques: Rutherford backscattering spectroscopy along a channeling direction (RBS-C), electron-energy loss spectroscopy (EELS), and Z-contrast images obtained in an aberration-corrected scanning transmission electron microscope. Range and deposited energy were simulated with SRIM-2008.04. The Z-contrast images from transmission electron microscope indicated: a near surface damaged layer ~30 nm thick, a subsurface region exhibiting "random" de-channeling ~52 nm thick, and a deeper damaged, crystalline zone ~64 nm thick. The RBS-C spectra confirmed the presence of these three regions. The two damaged regions contained high concentrations of as yet unresolved defect clusters. The intermediate region contained Zr-clusters embedded in an "amorphous" matrix that exhibited short-range order corresponding to -Al2O3, i.e., a defective spinel structure. The EELS measurements show that the amorphous region is deficient in oxygen.

Sina, Younes [University of Tennessee, Knoxville (UTK); McHargue, Carl J [University of Tennessee, Knoxville (UTK); Duscher, Gerd [University of Tennessee, Knoxville (UTK); Zhang, Yanwen [ORNL

2012-01-01

404

Strain effects on oxygen transport in tetragonal zirconium dioxide  

SciTech Connect

Temperature accelerated dynamics and molecular dynamics simulations are used to investigate the strain effects on oxygen interstitial and vacancy migration in tetragonal zirconium dioxide. At zero external strain, the anisotropic migration mechanisms of oxygen defects are characterized. At non-zero strains, both the crystal structure and defect migration barriers are modified by strain. Under compressive strains, the defect migration barrier increases with the increasing strain for both interstitials and vacancies. The crystal structure transforms from a tetragonal to a nearly cubic fluorite structure. Accordingly, the defect migration becomes nearly isotropic. Under dilative strains, the migration barrier first decreases then increases with increasing strain for both types of defects. The tetragonal phase transforms to a lower symmetry structure that is close to the orthorhombic phase. In turn, the defect migration becomes highly anisotropic. Under both compressive and dilative strains, interstitials respond to strain more strongly than vacancies. At small dilative strains, an oxygen interstitial has comparable diffusivity to a vacancy, suggesting that both types of defects can contribute to oxygen transport, if they are present. Although currently no previous result is available to validate oxygen interstitial diffusion behavior, the trend of strain effects on oxygen vacancy diffusion is in good agreement with available experimental and theoretical studies in the literature.

Xian-Ming Bai; Yongfeng Zhang; Michael R. Tonks

2013-11-01

405

Electrospun poly (vinyl alcohol)/ alpha-zirconium phosphate nanocomposite fibers  

NASA Astrophysics Data System (ADS)

Poly (vinyl alcohol) (PVA)/alpha-zirconium phosphate (ZrP) polymer nanocomposite (PNC) fibers were successfully prepared via the simple and low-cost electrospinning process. ZrP nanoparticles with two different dimensions, i.e., ZrP-500 with a lateral dimension of ca. 320 nm and an aspect ratio of ca. 500, and ZrP-1500 with a lateral dimension of ca. 950 nm and an aspect ratio of ca. 1500, were utilized to illustrate the size effect on the electrospun nanofibers. In order to obtain defect-free, uniform polymer nanocomposite fibers, a number of parameters including polymer concentration, feed rate, applied voltage and working distance between the needle tip and the fiber collecting substrate were investigated. Scanning electron microscopy (SEM) morphological analysis showed smooth and nonwoven electrospun nanofiber mat. Strong intermolecular interactions between the PVA matrix and the included ZrP nanofillers were revealed by the attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). The incorporation of ZrP nanofillers drastically improved the thermal stability of the PNC fibers. TGA results demonstrated a clear thermal stability dependence on the aspect ratio of the crystalline ZrP nanofillers. The degradation temperature was increased by 90 °C for the ZrP-1500 and 60 °C for ZrP-500 when the loading level was increased from 1% to 5%. Furthermore, the viscoelastic properties of the PNC solutions were studied by rheometer.

Lizu, Monira

406

High Purity Zirconium Tetrafluoride For Fluoride Glass Applications  

NASA Astrophysics Data System (ADS)

A totally anhydrous process has been developed for the preparation of high purity zirconium tetrafluoride for use in low loss fluoride glass applications. The ZrF4 purityis 99.99997% with respect to all transition elements (excluding HO based on analysis by spark source mass spectrometry (SSMS) and graphite furnace/atomic absorption spectroscopy (GF/AA). The only transition elements detected by these techniques were Fe, Ni and Cr, while Co and Cu were consistently below the detection limits. The anhydrous nature of the process, which is strictly maintained by the choice of reactants, affords product with very low oxide and hydroxide content. Total oxygen concentrations of less than 10 ppm have been measured by the inert gas fusion technique. A ZBLAN glass composition prepared using this ZrF4 showed extremely low UV absorption having an absorption constant of 1 cm-1 at 198 nm. ZrF4 from this process was also used in a ZBLAN glass fiber whose minimum optical loss was measured at 6.3 dB/km over 150 meters of fiber. The process is straightforward to scale up and has also been demonstrated to be useful for the preparation of HfF4, BaF2, A1F3 and LaF3.

Withers, Howard P.; Monk, V. A.; Cooper, G. A.

1989-06-01

407

Structural evolution of zirconium carbide under ion irradiation  

NASA Astrophysics Data System (ADS)

Zirconium carbide is one of the candidate materials to be used for some fuel components of the high temperature nuclear reactors planned in the frame of the Gen-IV project. Few data exist regarding its behaviour under irradiation. We have irradiated ZrC samples at room temperature with slow heavy ions (4 MeV Au, fluence from 10 11 to 5 × 10 15 cm -2) in order to simulate neutron irradiations. Grazing incidence X-Ray diffraction (GIXRD) and transmission electron microscopy (TEM) analysis have been performed in order to study the microstructural evolution of the material versus ion fluence. A high sensitivity to oxidation is observed with the formation of zirconia precipitates during the ion irradiations. Three damage stages are observed. At low fluence (<10 12 cm -2), low modifications are observed. At intermediate fluence, high micro-strains appear together with small faulted dislocation loops. At the highest fluence (>10 14 cm -2), the micro-strains saturate and the loops coalesce to form a dense dislocation network. No other structural modification is observed. The material shows a moderate cell parameter increase, corresponding to a 0.6 vol.% swelling, which saturates around 10 14 ions/cm 2, i.e., a few Zr dpa. As a result, in spite of a strong covalent bonding component, ZrC seems to have a behaviour under irradiation close to cubic metals.

Gosset, D.; Dollé, M.; Simeone, D.; Baldinozzi, G.; Thomé, L.

2008-02-01

408

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

409

Effects of fast neutron irradiation on zirconium carbide  

NASA Astrophysics Data System (ADS)

High-purity zone refined zirconium carbide has been fast neutron irradiated in the dose and temperature range of 1-10 × 10 25 N/m 2 ( E > 0.1 MeV) and 635-1480 °C, respectively. Non-irradiated and as-irradiated properties were measured including the lattice parameter, hardness and elastic modulus as determined through nano-indentation, thermal conductivity, and indentation fracture toughness. The effects of neutron irradiation on the microstructure were also determined though using transmission electron microscopy. The general finding of this paper, limited to this particular zone refined ZrC of nominal C/Zr ratio of 0.93, is that this ceramic is quite stable under neutron irradiation in the temperature and dose range studied. Measurement of lattice parameter before and after irradiation indicated a lack of significant crystalline strain due to irradiation. Only modest changes were observed in the mechanical properties of hardness, elastic modulus, and indentation fracture toughness. The thermal conductivity underwent a slight reduction near 1000 °C irradiation, though was essentially unchanged for 1300-1480 °C irradiation. Transmission electron microscopy revealed black-spot-type defects (likely Frank or other small loops) for irradiation at 670 °C, maturing to faulted Frank loops at 1280 °C. As the irradiation temperature increased from 1280 °C to the highest irradiation temperature, of 1496 °C, a transition to prismatic loops occurs.

Snead, Lance L.; Katoh, Yutai; Kondo, Sosuke

2010-04-01

410

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.

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

2013-10-01

411

Zirconium carbide thin films deposited by pulsed laser ablation  

NASA Astrophysics Data System (ADS)

A study of the laser ablation and deposition of zirconium carbide has been carried out in our laboratory. The target has been vaporised by a doubled Nd:YAG laser and the ablation plume has been characterised by time-of-flight mass spectrometry, emission spectroscopy and ultrafast imaging performed by an Intensified Coupled Charge Device (ICCD). The results show a single ablation mechanism in the whole range of laser fluence used in the experiments (0.5-15 J/cm2) and this is quite different from the case of TiC. The gas phase data are confirmed by the analysis of the films deposited on oriented silicon. In fact, by X-ray diffraction and subsequent XPS analysis, their composition is fluence independent leading to films with constant characteristics on a large range of experimental conditions. The difference between ZrC and TiC ablation mechanisms may be explained in terms of chemical-physical properties and thermodynamic considerations which can also clarify the gas phase composition.

D'Alessio, L.; Santagata, A.; Teghil, R.; Zaccagnino, M.; Zaccardo, I.; Marotta, V.; Ferro, D.; De Maria, G.

2000-12-01

412

The thermophysical properties of calcium and barium zirconium phosphate  

NASA Astrophysics Data System (ADS)

The thermophysical and structural properties of calcium and barium zirconium phosphate ceramics (CZP and BZP) have been investigated for their potential candidacy as actinide hosts for inert matrix fuels (IMF) in nuclear reactors. These phosphate ceramics, which can accommodate minor actinides as well as the resulting fission products, are found to be thermally stable to 1600 °C in air, however they begin to decompose in an inert atmosphere above approximately 1400 °C. The heat capacity, thermal conductivity and bulk thermal-expansion were measured from room temperature up to 1200 °C. Structural changes in this temperature region as well as the anisotropic thermal-expansion behaviour were studied using high-temperature X-ray diffraction. A phase change from R-3 to R-3c was identified for Ba0.5Zr2(PO4)3 near 880 °C. The thermal conductivity for these ceramics at 1000 °C was found to be 1.0 W m-1 K-1, a relatively low thermal conductivity that was increased to 5.0 W m-1 K-1 at 1000 °C for BZP:Ni (25:75 mass ratio) cermet composites.

Gregg, Daniel J.; Karatchevtseva, Inna; Triani, Gerry; Lumpkin, Gregory R.; Vance, Eric R.

2013-10-01

413

Synthesis and Characterization of Zirconium Tungstate Ultra-Thin Fibers  

SciTech Connect

This study reports an innovative method of electrospinning followed by pyrolysis to synthesize zirconium tungstate (ZrW2O8), a material with negative coefficient of thermal expansion (CTE), in ultra-thin fiber form. Morphologies and microstructures of the as-electrospun precursor fibers, the heat-treated intermediate fibers, and the final ZrW2O8 ultra-thin fibers were characterized by SEM, XRD, and TEM. The ZrW2O8 ultra-thin fibers had diameters in the sub-micrometer range with aspect ratios larger than 100; these fibers were polycrystalline, and consisted of single crystalline ZrW2O8 crystallites with sizes of 30-50 nm and surface roughness of several nanometers. The ZrW2O8 ultra-thin fibers are expected to outperform spherically, cylindrically, and/or irregularly shaped polycrystalline ZrW2O8 particles for the development of composites with precisely controlled CTEs. Additionally, this reported method could be utilized as a general approach to convert nano-scaled inorganic particles into fibers.

Zhang, Lifeng [South Dakota School of Mines and Technology; Howe, Jane Y [ORNL; Fong, Hao [South Dakota School of Mines and Technology; Zhang, Yan [Anhui Normal University, People's Republic of China

2009-01-01

414

The effect of zirconium implantation on the structure of sapphire  

NASA Astrophysics Data System (ADS)

The effect of zirconium implantation on the structure of sapphire was investigated by 175 keV Zr implantation at room temperature to a fluence of 4 × 1016 ions/cm2 into sapphire single crystals. Samples were examined by several experimental techniques: Rutherford backscattering spectroscopy along a channeling direction (RBS-C), electron-energy loss spectroscopy (EELS), and Z-contrast images obtained in an aberration-corrected scanning transmission electron microscope. Range and deposited energy were simulated with SRIM-2008.04. The Z-contrast images from transmission electron microscope indicated: a near surface damaged layer ˜30 nm thick, a subsurface region exhibiting "random" de-channeling ˜52 nm thick, and a deeper damaged, crystalline zone ˜64 nm thick. The RBS-C spectra confirmed the presence of these three regions. The two damaged regions contained high concentrations of as yet unresolved defect clusters. The intermediate region contained Zr-clusters embedded in an "amorphous" matrix that exhibited short-range order corresponding to ?-Al2O3, i.e., a defective spinel structure. The EELS measurements show that the amorphous region is deficient in oxygen.

Sina, Y.; McHargue, C. J.; Duscher, G.; Zhang, Y.

2012-09-01

415

The acid catalyzed nitration of methanol: formation of methyl nitrate via aerosol chemistry  

Microsoft Academic Search

The aqueous phase acid-catalyzed reaction of methanol (CH3OH) with nitric acid (HNO3) to yield methyl nitrate (CH3ONO2) under atmospheric conditions has been investigated using gas-phase infrared spectroscopy. Reactions were conducted in aqueous\\u000a sulfuric acid solutions (50.5–63.6 wt.%) with [CH3OH]?=?0.00005–0.005 M and [HNO3]?=?0.02–0.21 M, at 278.2–328.6 K. Methyl nitrate production rates increased linearly with CH3OH and HNO3 concentrations and exponentially with sulfuric acid weight percent

Laura T. Iraci; Brent G. Riffel; Carly B. Robinson; Rebecca R. Michelsen; Rachel M. Stephenson

2007-01-01

416

Properties and thermal decomposition of the double salts of uranyl nitrate-ammonium nitrate  

Microsoft Academic Search

The formation of ammonium nitrate-uranyl nitrate double salts has important effects on the thermal denitration process for the preparation of UOâ and on the physical properties of the resulting product. Analyses were performed, and properties and decomposition behavior were determined for three double salts: NHâUOâ(NOâ)â, (NHâ)âUOâ(NOâ)â, and (NHâ)âUOâ(NOâ)â {center dot} 2HâO. The trinitrate salt decomposes without melting at 270--300°C to

Karl J. Notz; Paul A. Haas

1989-01-01

417

Cold neutron prompt gamma activation analysis, a non-destructive technique for hydrogen level assessment in zirconium alloys  

E-print Network

assessment in zirconium alloys Adrien Couet a, , Arthur T. Motta a , Robert J. Comstock b , Rick L. Paul c to quantitatively assess hydrogen concentration in zirconium alloys. The technique, called Cold Neutron Prompt Gamma alloy nuclear fuel cladding and the associated hydrogen pick-up can become a life-limiting degradation

Motta, Arthur T.

418

Identification of anisotropic Hill criteria from the channel die compression test. Application to a normal anisotropy of zirconium 702alpha  

Microsoft Academic Search

During the last years the study of the plastic deformation modes and the anisotropic mechanical behavior of zirconium alloys have been the subject of many investigations. This paper deals with a phenomenological identification of an anisotropic Hill constitutive equation of zirconium 702alpha samples using channel die compression at room temperature. Generally, by considering the different possible orientations of the samples

A. Gavrus; H. Francillette

2003-01-01

419

A Lotus japonicus mutant defective in nitrate uptake is also affected in the nitrate response to nodulation.  

PubMed

A chlorate-resistant mutant (Ljclo1) of the model legume Lotus japonicus was identified that showed normal levels of nitrate reductase enzyme activity but had decreased uptake of nitrate, as determined from nitrate depletion and electrophysiological measurements. The data suggest that the mutant could be affected specifically in the low-affinity but not in the high-affinity nitrate transport system, and also showed decreased uptake of chlorate. Back-crosses of the mutant plant to the wild type indicated that it is affected in a single Mendelian recessive trait. Thus, the mutation produced in Ljclo1 may be related to some of the low-affinity nitrate transporters or to a regulatory mechanism associated with nitrate/chlorate uptake. Both size and chlorophyll content in young leaves of the mutant plants were significantly reduced compared to the wild type. In addition, nodulation performance of the mutant plants was similar to the wild type in the absence of any exogenous nitrate. However, the nodule:root biomass ratio in mutant plants was considerably reduced in the presence of 1-2 mm nitrate. The levels of several transcripts for nitrate transport and assimilation genes were determined for the wild type and mutant plants and were slightly different. The results suggest interdependence between nitrate uptake, plant growth and nodulation in Ljclo1 mutant plants. PMID:24673996

Pal'ove-Balang, P; García-Calderón, M; Pérez-Delgado, C M; Pavlovkin, J; Betti, M; Márquez, A J

2015-01-01

420

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

421

Sustainability of natural attenuation of nitrate in agricultural aquifers  

USGS Publications Warehouse

Increased concentrations of nitrate in groundwater in agricultural areas, coinciding with increased use of chemical and organic fertilizers, have raised concern because of risks to environmental and human health. At some sites, these problems are mitigated by natural attenuation of nitrate as a result of microbially mediated reactions. Results from U.S. Geological Survey (USGS) research under the National Water-Quality Assessment (NAWQA) program show that reactions of dissolved nitrate with solid aquifer minerals and organic carbon help lower nitrate concentrations in groundwater beneath agricultural fields. However, increased fluxes of nitrate cause ongoing depletion of the finite pool of solid reactants. Consumption of the solid reactants diminishes the capacity of the aquifer to remove nitrate, calling into question the long-term sustainability of these natural attenuation processes.

Green, Christopher T.; Bekins, Barbara A.

2010-01-01

422

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

423

Evaluation of nitrate reductase activity in Rhizobium japonicum  

SciTech Connect

Nitrate reductase activity was evaluated by four approaches, using four strains of Rhizobium japonicum and 11 chlorate-resistant mutants of the four strains. It was concluded that in vitro assays with bacteria or bacteroids provide the most simple and reliable assessment of the presence or absence of nitrate reductase. Nitrite reductase activity with methyl viologen and dithionite was found, but the enzyme activity does not confound the assay of nitrate reductase. 18 references

Streeter, J.G.; DeVine, P.J.

1983-08-01

424

Nitrate and nitrite in biology, nutrition and therapeutics  

PubMed Central

Inorganic nitrate and nitrite from endogenous or dietary sources are metabolized in vivo to nitric oxide (NO) and other bioactive nitrogen oxides. The nitrate-nitrite-NO pathway is emerging as an important mediator of blood flow regulation, cell signaling, energetics and tissue responses to hypoxia. The latest advances in our understanding of the biochemistry, physiology and therapeutics of nitrate, nitrite and NO were discussed during a recent two-day meeting at the Nobel Forum, Karolinska Institutet in Stockholm. PMID:19915529

Lundberg, Jon O.; Gladwin, Mark T.; Ahluwalia, Amrita; Benjamin, Nigel; Bryan, Nathan S.; Butler, Anthony; Cabrales, Pedro; Fago, Angela; Feelisch, Martin; Ford, Peter C.; Freeman, Bruce A.; Frenneau, Michael; Friedman, Joel; Kelm, Malte; Kevil, Christopher G.; Kim-Shapiro, Daniel B.; Kozlov, Andrey V.; Lancaster, Jack R.; Lefer, David J.; McColl, Kenneth; McCurry, Kenneth; Patel, Rakesh; Petersson, Joel; Rassaf, Tienush; Reutov, Valentin P.; Richter-Addo, George B.; Schechter, Alan; Shiva, Sruti; Tsuchiya, Koichiro; van Faassen, Ernst E.; Webb, Andrew J.; Zuckerbraun, Brian S.; Zweier, Jay L.; Weitzberg, Eddie

2014-01-01

425

Nitrate Paradigm Does Not Hold Up for Sugarcane  

PubMed Central

Modern agriculture is based on the notion that nitrate is the main source of nitrogen (N) for crops, but nitrate is also the most mobile form of N and easily lost from soil. Efficient acquisition of nitrate by crops is therefore a prerequisite for avoiding off-site N pollution. Sugarcane is considered the most suitable tropical crop for biofuel production, but surprisingly high N fertilizer applications in main producer countries raise doubt about the sustainability of production and are at odds with a carbon-based crop. Examining reasons for the inefficient use of N fertilizer, we hypothesized that sugarcane resembles other giant tropical grasses which inhibit the production of nitrate in soil and differ from related grain crops with a confirmed ability to use nitrate. The results of our study support the hypothesis that N-replete sugarcane and ancestral species in the Andropogoneae supertribe strongly prefer ammonium over nitrate. Sugarcane differs from grain crops, sorghum and maize, which acquired both N sources equally well, while giant grass, Erianthus, displayed an intermediate ability to use nitrate. We conclude that discrimination against nitrate and a low capacity to store nitrate in shoots prevents commercial sugarcane varieties from taking advantage of the high nitrate concentrations in fertilized soils in the first three months of the growing season, leaving nitrate vulnerable to loss. Our study addresses a major caveat of sugarcane production and affords a strong basis for improvement through breeding cultivars with enhanced capacity to use nitrate as well as through agronomic measures that reduce nitrification in soil. PMID:21552564

Robinson, Nicole; Brackin, Richard; Vinall, Kerry; Soper, Fiona; Holst, Jirko; Gamage, Harshi; Paungfoo-Lonhienne, Chanyarat; Rennenberg, Heinz; Lakshmanan, Prakash; Schmidt, Susanne

2011-01-01

426

Nitrate paradigm does not hold up for sugarcane.  

PubMed

Modern agriculture is based on the notion that nitrate is the main source of nitrogen (N) for crops, but nitrate is also the most mobile form of N and easily lost from soil. Efficient acquisition of nitrate by crops is therefore a prerequisite for avoiding off-site N pollution. Sugarcane is considered the most suitable tropical crop for biofuel production, but surprisingly high N fertilizer applications in main producer countries raise doubt about the sustainability of production and are at odds with a carbon-based crop. Examining reasons for the inefficient use of N fertilizer, we hypothesized that sugarcane resembles other giant tropical grasses which inhibit the production of nitrate in soil and differ from related grain crops with a confirmed ability to use nitrate. The results of our study support the hypothesis that N-replete sugarcane and ancestral species in the Andropogoneae supertribe strongly prefer ammonium over nitrate. Sugarcane differs from grain crops, sorghum and maize, which acquired both N sources equally well, while giant grass, Erianthus, displayed an intermediate ability to use nitrate. We conclude that discrimination against nitrate and a low capacity to store nitrate in shoots prevents commercial sugarcane varieties from taking advantage of the high nitrate concentrations in fertilized soils in the first three months of the growing season, leaving nitrate vulnerable to loss. Our study addresses a major caveat of sugarcane production and affords a strong basis for improvement through breeding cultivars with enhanced capacity to use nitrate as well as through agronomic measures that reduce nitrification in soil. PMID:21552564

Robinson, Nicole; Brackin, Richard; Vinall, Kerry; Soper, Fiona; Holst, Jirko; Gamage, Harshi; Paungfoo-Lonhienne, Chanyarat; Rennenberg, Heinz; Lakshmanan, Prakash; Schmidt, Susanne

2011-01-01

427

Containerless Liquid to Solid Nucleation Pathways in Two Representative Grades of Commercially Available Zirconium  

NASA Technical Reports Server (NTRS)

Experimental measurements were conducted to determine the solid metal nucleation pathways of radiatively cooling, molten zirconium spheres of two different commercially available purity grades in a high-vacuum, high-temperature electrostatic levitator. The ensemble distribution of maximum undercooling temperatures was interpreted using Poisson statistics to determine the temperature dependence of the solid metal nucleation rate. For a sample of nominally 99.95% pure zirconium, the results are consistent with heterogeneous solid metal nucleation either on static catalyst particles at least approx. 30 nm diameter or on a surface coating. For a sample of nominally 99% pure zirconium, however, it appears that heterogeneous solid metal nucleation occurred either on a polydispersion of approx. 10 nm (mean diameter) static catalyst particles or on dynamic catalyst particles that precipitated from a solution that became supersaturated as the melt cooled.

Rulison, A. J.; Rhim, W.-K.; Bayuzick, R.; Hofmeister, W.; Morton, C.

1997-01-01

428

Hydrogen Embrittlement in Zirconium: a Quasi-Continuum Density Functional Theory Study  

NASA Astrophysics Data System (ADS)

The hydrogen embrittlement in Zirconium becomes a very important and emergent issue for academia, industry and policy makers as a result of the Japan nuclear accident. The hydride formation, diffusion and embrittlement in zircolay will impact dramatically on the development of advanced nuclear energy systems, the life time extension of the current nuclear fleet and dry storage of spent nuclear fuel. Quasi-Continuum Density Functional Theory (QCDFT) is a powerful concurrent multiscale method based entirely on density functional theory (DFT) and allows quantum simulations of materials properties of a large system with billions of atoms. Using QCDFT modeling, we found that the presents of hydrogen at the cracktip of zirconium, both on crack surface and in-bulk, will form zirconium hydrides and embrittle the system. The concentration of hydrogen and orientation of crack plays important roles in such embrittlement. The mechanism of hydrogen embrittlement under various loading conditions will be discussed.

Peng, Q.

2012-02-01

429

Hypersensitivity pneumonitis and exposure to zirconium silicate in a young ceramic tile worker.  

PubMed

We describe a nonsmoking ceramic tile worker 25 yr of age who developed a worsening dry cough and dyspnea after 3.5 yr as a sorter and glazer of tiles. Open lung biopsy revealed an intense granulomatous interstitial pneumonia with mild fibrosis, compatible with hypersensitivity pneumonitis, and numerous very small birefringent crystals around the terminal airways and occasionally in granulomas. Pulmonary particle analysis revealed an inhaled dust burden nearly 100-fold the normal background level, mainly consisting of clay minerals and zirconium silicate. The patient had no history or clinical or laboratory findings suggesting any organic etiologic agent. A sarcoid granulomatosis type of chronic pulmonary hypersensitivity reaction is known after long-term exposure to zirconium, but this case demonstrates that zirconium can also cause an acute and fulminant allergic alveolitislike hypersensitivity reaction. PMID:8214930

Liippo, K K; Anttila, S L; Taikina-Aho, O; Ruokonen, E L; Toivonen, S T; Tuomi, T

1993-10-01

430

Theoretical study of the reaction between 2,2???,4???-trihydroxyazobenzene-5-sulfonic acid and zirconium  

USGS Publications Warehouse

Zirconium reacts with 2,2???,4???-trihydroxyazobenzene-5-sulfonic acid in acid solutions to Form two complexes in which the ratios of dye to zirconium are 1 to 1 and 2 to 1. Both complexes are true chelates, with zirconium acting as a bridge between the two orthohydroxy dye groups. Apparent equilibrium constants for the reactions to form each of the complexes are determined. The reactions are used as a basis for the determination of the active component in the dye and a graphical method for the determination of reagent purity is described. Four absorption spectra covering the wave length region from 350 to 750 m?? are given, which completely define the color system associated with the reactions in solutions where the hydrochloric acid concentration ranges from 0.0064N to about 7N.

Fletcher, M.H.

1960-01-01

431

Review of Cernox™ (Zirconium Oxy-Nitride) Thin-Film Resistance Temperature Sensors  

NASA Astrophysics Data System (ADS)

Cernox™ resistance thermometers were commercially introduced in 1993. The Cernox™ temperature-sensing element is fabricated from zirconium reactively sputtered in a nitrogen-oxygen atmosphere. The resulting thin film is comprised of conducting zirconium nitride embedded within a zirconium oxide nonconducting matrix. This material has a negative temperature coefficient of resistance making it useful as a temperature sensor. The ratio of conducting to nonconducting material can be varied to tailor the sensor to a given temperature range. A single device can be fabricated for use from below 0.3 K to 420 K. Cernox™ temperature sensors possess many attributes desirable in a temperature sensor including high sensitivity, excellent short-term and long-term stability, small physical size, fast thermal response and small calibration shifts when exposed to magnetic fields or ionizing radiation. This paper presents a review of Cernox™ temperature sensors with regard to their physical, thermometric and operational properties and environmental effects.

Courts, S. Scott; Swinehart, Philip R.

2003-09-01

432

Simulating the corrosion of zirconium alloys in the water coolant of VVER reactors  

NASA Astrophysics Data System (ADS)

A model for predicting the corrosion of cladding zirconium alloys depending on their composition and operating conditions is proposed. Laws of thermodynamics and chemical kinetics of the reactions through which the multicomponent zirconium alloy is oxidized in the reactor coolant constitute the physicochemical heart of the model. The developed version of the model is verified against the results obtained from tests of fuel rod claddings made of commercial-grade and experimental zirconium alloys carried out by different researchers under autoclave and reactor conditions. It is shown that the proposed model adequately describes the corrosion of alloys in coolants used at nuclear power stations. It is determined that, owing to boiling of coolant and its acidification in a VVER-1200 reactor, Zr-1% Nb alloys with additions of iron and oxygen must be more resistant to corrosion than the commercial-grade alloy E110.

Kritskii, V. G.; Berezina, I. G.; Motkova, E. A.

2013-07-01

433

Determination of fluoride in water - A modified zirconium-alizarin method  

USGS Publications Warehouse

A convenient, rapid colorimetric procedure using the zirconium-alizarin indicator acidified with sulfuric acid for the determination of fluoride in water is described. Since this acid indicator is stable indefinitely, it is more useful than other zirconium-alizarin reagents previously reported. The use of sulfuric acid alone in acidifying the zirconium-alizarin reagent makes possible the maximum suppression of the interference of sulfate. Control of the pH of the samples eliminates errors due to the alkalinity of the samples. The fluoride content of waters containing less than 500 parts per million of sulfate and less than 1000 p.p.m. of chloride may be determined within a limit of 0.1 p.p.m. when a 100-ml. sample is used.

Lamar, W.L.

1945-01-01

434

Synthesis, Spectroscopic, and Biological Studies on New Zirconium(IV) Porphyrins with Axial Ligand  

PubMed Central

A series of parasubstituted tetraphenylporphyrin zirconium(IV) salicylate complexes (SA/5-SSAZr(IV)RTPP, R = p-H, p-CH3, p-NO2, p-Cl, SA = salicylate, and 5-SSA = 5-sulfosalicylate) have been synthesized, and the spectral properties of free base porphyrins, their corresponding metallated, and axially ligated zirconium(IV) porphyrin compounds were compared with each other. A detailed analysis of ultraviolet-visible (UV-vis), proton nulcear magnetic resonance (1H NMR) spectroscopy, infrared (IR) spectroscopy, and elemental analysis suggested the transformation from free base porphyrins to zirconium(IV) porphyrins. The ability of the metal in this complex for extra coordination of solvent molecules was confirmed by ESI-MS spectra. Besides the fluorescence, cyclic voltammetry, and thermogravimetric studies, the complexes were also screened for antimicrobial and anticancer activities. Among all the complexes, 5-SSAZr(p-NO2TPP) shows high antibacterial activity. PMID:24106455

Bajju, Gauri D.; Devi, Gita; Katoch, Sapna; Bhagat, Madhulika; Deepmala; Ashu; Kundan, Sujata; Anand, Sunil Kumar

2013-01-01

435

Myocardial postconditioning is lost in vascular nitrate tolerance.  

PubMed

Organic nitrates play an important role in the therapy of ischemic heart disease; however, their clinical application is limited by the development of vascular nitrate tolerance. We have previously shown attenuation of the cardioprotective effect of preconditioning in vascular nitrate tolerance. Here, we studied whether the development of vascular nitrate tolerance affects the infarct size, limiting effect of ischemic postconditioning (IPost) in the myocardium, and whether the activation of survival kinases plays a role in the molecular mechanism of postconditioning in the presence or absence of vascular nitrate tolerance. Male Wistar rats were treated with nitroglycerin/vehicle for 3 days to induce vascular nitrate tolerance. On the fourth day, isolated hearts were subjected to 30-minute coronary occlusion followed by 120-minute reperfusion with or without IPost. In nontolerant hearts, postconditioning significantly decreased infarct size as compared with ischemia/reperfusion; however, postconditioning failed to decrease infarct size in hearts of nitrate tolerant rats. Phosphorylation of ERK 1/2, Akt, or endothelial nitric oxide synthetase showed no significant differences between the groups at the 10th minute of reperfusion. Vascular nitrate tolerance interferes with the infarct size limiting effect of IPost. Activation of survival kinases is not crucial in the molecular mechanism of postconditioning, which remains unaffected in nitrate tolerance. PMID:23669719

Fekete, Veronika; Murlasits, Zsolt; Aypar, Eda; Bencsik, Péter; Sárközy, Márta; Szénási, Gábor; Ferdinandy, Péter; Csont, Tamás

2013-09-01

436

Nitrate Leaching from Intensive Fiber Production on Abandoned Agricultural Land  

SciTech Connect

Paper outlines nitrate leaching results of loblolly pine and sweet gum that were grown with irrigation, continuous fertilization and insect pest control on a year old abandoned peanut field. Wells and tension lysimeters were used to measure nitrate in soil moisture and groundwater on three replicate transects for two years. Groundwater nitrate concentration beneath the minimum treatment was much higher than the maximum treatment and old field. All three treatments often exceeded the drinking water standard. Forest and lake edge had low levels while the soil moisture nitrate concentrations in the two plantation treatments were much higher than the old field.

Williams, T.M.

1999-01-01

437

Aluminum nitrate recrystallization and recovery from liquid extraction raffinates  

SciTech Connect

The solid sludges resulting form biodenitrification of discarded aluminum nitrate are the largest Y-12 Plant process solid waste. Aluminum nitrate feedstocks also represent a major plant materials cost. The chemical constraints on aluminum nitrate recycle were investigated to determine the feasibility of increasing recycle while maintaining acceptable aluminum nitrate purity. Reported phase behavior of analogous systems, together with bench research, indicated that it would be possible to raise the recycle rate from 35% to between 70 and 90% by successive concentration and recrystallization of the mother liquor. A full scale pilot test successfully confirmed the ability to obtain 70% recycle in existing process equipment.

Griffith, W.L.; Compere, A.L.; Googin, J.M.; Huxtable, W.P.

1991-09-01

438

Identification and characterization of the Staphylococcus carnosus nitrate reductase operon.  

PubMed

Physiological and genetic characterization of Staphylococcus carnosus nitrate reductase-negative mutants led to the identification of the nitrate reductase operon, narGHJI. Transcription from the nar promoter was stimulated by anaerobiosis, nitrate, and nitrite. This is in accordance with the nitrate reductase activities determined with benzyl viologen as electron donor. However, in the presence of oxygen and nitrate, high transcriptional initiation but low nitrate reductase activity was observed. Since the alphabeta complex of the nitrate reductase formed during anaerobic growth was insensitive to oxygen, other oxygen-sensitive steps (e.g., post-transcriptional mechanisms, molybdenum cofactor biosynthesis) must be involved. The nitrate-reducing system in S. carnosus displays similarities to the dissimilatory nitrate reductases of Escherichia coli. However, in the S. carnosus nar promoter, no obvious Fnr and integration host factor recognition sites are present; only one site that is related to the E. coli NarL consensus sequence was found. Studies to determine whether the E. coli proteins NarL and Fnr are functional at the S. carnosus narGHJI promoter indicated that the promoter is not functional in E. coli. PMID:9738886

Pantel, I; Lindgren, P E; Neubauer, H; Götz, F

1998-07-01

439

Who is drinking nitrate in their well water?  

SciTech Connect

This study evaluated the health risks for a rural northeastern Oregon population which is exposed to high nitrate levels in well water. The study also identified possible sources of nitrate contamination, and investigated measures the resident had taken to reduce their nitrate exposure from well water. Three data sets were used in the study, including a telephone survey of the residents, existing information collected by the Oregon Department of Environmental Quality about well water nitrate concentrations, and demographic information from census records. Results revealed that 23% of the surveyed population was drinking well water that contained nitrate in excess of the 10 ppm nitrate-nitrogen maximum contaminant level adopted by the US Environmental Protection Agency for drinking water. Seventy-two percent of the households with nitrate levels exceeding the 10 ppm level did not use devices that effectively remove nitrates. The population included few women of childbearing age, and was generally older than other nearby urban or rural populations. Resident infants were not exposed to well water nitrate in excess of the 10 ppm level, and were therefore not at apparent risk for methemoglobinemia (blue-baby syndrome). Although the risk of infant methemoglobinemia was low in this area, it is recommended that alternative water sources be explored, and that follow-up monitoring be performed by state and/or local agencies.

Mitchell, T.J.; Harding, A.K. [Oregon State Univ., Corvallis, OR (United States). Dept. of Public Health

1996-10-01

440

Eutectic composite explosives containing ammonium nitrate  

SciTech Connect

The eutectic of ammonium nitrate (AN), the ammonium salt of 3,5-dinitro-1,2,4-triazole was prepared and its sensitivity and performance were studied. It was found that this AN formulation was unusual in that it performed ideally at small diameter, which indicated that it was a monomolecular explosive. Sensitivity tests included type 12 impact, Henkin thermal and wedge tests, and performance tests included rate stick/plate dent, cylinder, and aquarium tests. Results were compared with calculations, standard explosives, and another eutectic, ethylendiamine dinitrate (EDD)/AN.

Stinecipher, M.M.

1981-01-01

441

Combustion of transition-metal ethylenediamine nitrates  

SciTech Connect

This article examines the burning of the coordinated nitrates of Cu, Cr, Co, Ni and Zn, in which ethylenediamine is the burning part of the molecule. The burning rates of these compounds are determined at pressures up to 10 MPa produced by compressed nitrogen. Results from thermochemical calculations, the combustion rates, and the temperatures corresponding to the ignition delays are given. The burning rates of the ethylenediamine compounds are compared with those of ammonia compounds. It is determined that the ammonia compounds of Cu, Co, and Ni at 10 MPa burn 1.4-1.8 times more rapidly than the corresponding ethylenediamine compounds.

Gorbunov, V.V.; Shidlovskii, A.A.; Shmagin, L.F.

1983-09-01

442

Electrospun cellulose nitrate and polycaprolactone blended nanofibers  

NASA Astrophysics Data System (ADS)

Pure cellulose nitrate (CN) and blends of CN and polycaprolactone were electrospun to form nonwoven mats. Polymers were dissolved in a mixed solvent system of tetrahydrofuran and N,N-dimethylformamide. The concentrations were varied to obtain sub-micron and nanoscale fiber mats. Fiber mats were analyzed using scanning electron microscopy, contact angle analysis, Fourier transform infrared spectroscopy and thermal gravimetric analysis. The fiber morphology, surface chemistry and contact angle data show that these electrospun materials are suitable for applications including biosensing, biomedical and tissue engineering.

Nartker, Steven; Hassan, Mohamed; Stogsdill, Michael

2015-03-01

443

Bayesian model selection validates a biokinetic model for zirconium processing in humans  

PubMed Central

Background In radiation protection, biokinetic models for zirconium processing are of crucial importance in dose estimation and further risk analysis for humans exposed to this radioactive substance. They provide limiting values of detrimental effects and build the basis for applications in internal dosimetry, the prediction for radioactive zirconium retention in various organs as well as retrospective dosimetry. Multi-compartmental models are the tool of choice for simulating the processing of zirconium. Although easily interpretable, determining the exact compartment structure and interaction mechanisms is generally daunting. In the context of observing the dynamics of multiple compartments, Bayesian methods provide efficient tools for model inference and selection. Results We are the first to apply a Markov chain Monte Carlo approach to compute Bayes factors for the evaluation of two competing models for zirconium processing in the human body after ingestion. Based on in vivo measurements of human plasma and urine levels we were able to show that a recently published model is superior to the standard model of the International Commission on Radiological Protection. The Bayes factors were estimated by means of the numerically stable thermodynamic integration in combination with a recently developed copula-based Metropolis-Hastings sampler. Conclusions In contrast to the standard model the novel model predicts lower accretion of zirconium in bones. This results in lower levels of noxious doses for exposed individuals. Moreover, the Bayesian approach allows for retrospective dose assessment, including credible intervals for the initially ingested zirconium, in a significantly more reliable fashion than previously possible. All methods presented here are readily applicable to many modeling tasks in systems biology. PMID:22863152

2012-01-01

444

Solid-phase zirconium and fluoride species in alkaline zircaloy cladding waste at Hanford.  

PubMed

The United States Department of Energy Hanford Site, near Richland, Washington, USA, processed plutonium between 1944 and 1987. Fifty-six million gallons of waste of various origins remain, including waste from removing zircaloy fuel cladding using the so-called Zirflex process. The speciation of zirconium and fluoride in this waste is important because of the corrosivity and reactivity of fluoride as well as the (potentially) high density of Zr-phases. This study evaluates the solid-phase speciation of zirconium and fluoride using X-ray diffraction (XRD) and scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS). Two waste samples were analyzed: one waste sample that is relatively pure zirconium cladding waste from tank 241-AW-105 and another that is a blend of zirconium cladding wastes and other high-level wastes from tank 241-C-104. Villiaumite (NaF) was found to be the dominant fluoride species in the cladding waste and natrophosphate (Na7F[PO4]2 · 19H2O) was the dominant species in the blended waste. Most zirconium was present as a sub-micron amorphous Na-Zr-O phase in the cladding waste and a Na-Al-Zr-O phase in the blended waste. Some zirconium was present in both tanks as either rounded or elongated crystalline needles of Na-bearing ZrO2 that are up to 200 ?m in length. These results provide waste process planners the speciation data needed to develop disposal processes for this waste. PMID:24976128

Reynolds, Jacob G; Huber, Heinz J; Cooke, Gary A; Pestovich, John A

2014-08-15

445

The development of nitrate reductase in Chlorella and its repression by ammonium  

Microsoft Academic Search

Chlorella vulgaris, grown with ammonium sulphate as nitrogen source, contains very little nitrate reductase activity in contrast to cells grown with potassium nitrate. When ammonium-grown cells are transferred to a nitrate medium, nitrate reductase activity increases rapidly and the increase is partially prevented by chloramphenicol and by p-fluorophenylalanine, suggesting that protein synthesis is involved. The increase in nitrate reductase activity

I. Morris; P. J. Syrett

1963-01-01

446

STUDIES ON THE PREPARATION AND PROPERTIES OF URANIUM(IV) NITRATE  

Microsoft Academic Search

Uranium(IV) nitrate was prepared by photochemical reduction of uranyl ; nitrate in the presence of ethanol and by reacting uraniun(IV) sulfate and barium ; nitrate or uranium(IV) chloride with silver nitrate. Hexavalent uranium was ; separated from the tetravalent uranium by, solvent extraction with 5 to 10% ; tributyl phosphate (TBP) solution in kerosene and later uranium(IV) nitrate was ;

T. R. Bhat; B. S. Mathur

1963-01-01

447

Molecular basis of nitrate uptake by the plant nitrate transporter NRT1.1  

PubMed Central

Summary The NRT1/PTR family of proton-coupled transporters are responsible for nitrogen assimilation in eukaryotes and bacteria through the uptake of peptides. However, in the majority of plant species members of this family have evolved to transport nitrate as well as additional secondary metabolites and hormones. In response to falling nitrate levels, NRT1.1 is phosphorylated on an intracellular threonine that switches the transporter from a low to high affinity state. Here we present both the apo and nitrate bound crystal structures of Arabidopsis thaliana NRT1.1, which together with in vitro binding and transport data identify a key role for His356 in nitrate binding. Our data support a model whereby phosphorylation increases structural flexibility and in turn the rate of transport. Comparison with peptide transporters further reveals how the NRT1/PTR family has evolved to recognize diverse nitrogenous ligands, whilst maintaining elements of a conserved coupling mechanism within this superfamily of nutrient transporters. PMID:24572366

Parker, Joanne L.; Newstead, Simon

2014-01-01

448

Developmental stage-specific and nitrate-independent regulation of nitrate reductase gene expression in rapeseed.  

PubMed Central

cDNA clones for two isogenes of nitrate reductase (NR) have been isolated from rapeseed (Brassica napus L.) androgenetic haploid embryos induced by microspore culture. NR mRNA accumulation can be detected by northern hybridization at 14 d after culture initiation when embryos develop to the heart/torpedo-shaped stage. Whole-mount in situ hybridization experiments demonstrate that the mRNA accumulation is developmental stage specific. In addition, even when cultured in media containing no nitrate, embryos accumulated NR mRNA to almost the same level as the control. This indicates the unique regulation of NR in embryogenesis in which NR mRNA transcription is activated in a developmental stage-specific manner that is independent of nitrate induction. In zygotic embryogenesis, a stage-specific accumulation of NR mRNA was also observed. By contrast, the obvious effect of nitrate on NR expression that has been reported in many plant species was also confirmed in rapeseed leaf. Quantitative combined reverse transcription-polymerase chain reaction analysis suggests that the flexible and variable regulation of NR expression, which is organ specific, nitrogen metabolite specific, and developmental stage specific, is caused principally by regulation of one major structural gene. PMID:8685274

Fukuoka, H; Ogawa, T; Minami, H; Yano, H; Ohkawa, Y

1996-01-01

449

A comparative study between two citrus rootstocks: Effect of nitrate on the root morpho-topology and net nitrate uptake  

Microsoft Academic Search

Root morpho-topology and net nitrate uptake of two citrus seedlings, Volkamer Lemon and Carrizo Citrange, grown at two nitrogen supplies (NO3-N 5 µM and 1000 µM, respectively) were studied. Root morphological and topological parameters were gauged by an image-specific analysis system (WinRHIZO). Net nitrate uptake was estimated using the nitrate depletion method. The main findings showed that Carrizo seedlings had a dichotomous

Agostino Sorgonà; Maria Rosa Abenavoli; Giovanni Cacco

2005-01-01

450

Mutation of the Arabidopsis NRT1.5 Nitrate Transporter Causes Defective Root-to-Shoot Nitrate Transport  

Microsoft Academic Search

Little is known about the molecular and regulatory mechanisms of long-distance nitrate transport in higher plants. NRT1.5 is one of the 53 Arabidopsis thaliana nitrate transporter NRT1 (Peptide Transporter PTR) genes, of which two members, NRT1.1 (CHL1 for Chlorate resistant 1) and NRT1.2, have been shown to be involved in nitrate uptake. Functional analysis of cRNA-injected Xenopus laevis oocytes showed

Shan-Hua Lin; H.-F. Kuo; G. Canivenc; C.-S. Lin; M. Lepetit; P.-K. Hsu; P. Tillard; H.-L. Lin; Y.-Y. Wang; C.-B. Tsai; A. Gojon; Y.-F. Tsay

2008-01-01

451

Bonding of sapphire to sapphire by eutectic mixture of aluminum oxide and zirconium oxide  

NASA Technical Reports Server (NTRS)

An element comprising sapphire, ruby or blue sapphire can be bonded to another element of such material with a eutectic mixture of aluminum oxide and zirconium oxide. The bonding mixture may be applied in the form of a distilled water slurry or by electron beam vapor deposition. In one embodiment the eutectic is formed in situ by applying a layer of zirconium oxide and then heating the assembly to a temperature above the eutectic temperature and below the melting point of the material from which the elements are formed. The formation of a sapphire rubidium maser cell utilizing eutectic bonding is shown.

Deluca, J. J. (inventor)

1979-01-01

452

Bonding of sapphire to sapphire by eutectic mixture of aluminum oxide and zirconium oxide  

NASA Technical Reports Server (NTRS)

Bonding of an element comprising sapphire, ruby or blue sapphire to another element of such material with a eutectic mixture of aluminum oxide and zirconium oxide is discussed. The bonding mixture may be applied in the form of a distilled water slurry or by electron beam vapor deposition. In one embodiment the eutectic is formed in situ by applying a layer of zirconium oxide and then heating the assembly to a temperature above the eutectic temperature and below the melting point of the material from which the elements are formed. The formation of a sapphire rubidium maser cell utilizing eutectic bonding is shown.

Deluca, J. J. (inventor)

1975-01-01

453

Thermal Decomposition and Desorption of Diethylamido of Tetrakis (Diethylamido)Zirconium (TDEAZr) on Si(100)  

Microsoft Academic Search

The thermal decomposition pathway and desorption of diethylamido of tetrakis (diethylamido)zirconium [TDEAZr, Zr(N(C2H5)2) 4] on Si(100) were studied using temperature-programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS). During TPD experiments, ethylethyleneimine (C2H5N=CHCH3), diethylamine [NH(C2H5)2], acetonitrile (CH3CN), ethylene (C2H4) and hydrogen (H2) desorbed as the main decomposition products of diethylamido, which was chemisorbed on Si(100) through the scission of the zirconium-diethylamido

Joonhee Jeong; Sungwon Lim; Kijung Yong

2003-01-01

454

Methyl iodide as a promoter of the SCC of zirconium alloys in iodine vapour  

NASA Astrophysics Data System (ADS)

The presence of organic-iodine contaminants, or specifically methyl iodide, in the iodine environment during stress corrosion tests leads to an increased frequency of crack nucleation, and possibly a more rapid crack propagation process. The unusual fractographic features associated with these impurities suggest that they enhance the reduction in the surface energy of zirconium, cause an instability in the propagating crack front, and possibly enhance the rate of reaction to form zirconium iodides. These impurities are the most potent catalysts of iodine-induced cracking so far identified, although methyl iodide alone cannot initiate cracking.

Cox, B.; Haddad, R.

1986-01-01

455

Stress corrosion cracking of zirconium cladding tubes: I. Proximate local SCC testing method  

NASA Astrophysics Data System (ADS)

The stress corrosion cracking (SCC) methods of testing zirconium cladding tubes are analyzed. A proximate method is proposed for estimating SCC of fuel claddings claddings in a iodine-containing environment with a limited contact zone between a metal and corrosive medium and simultaneous measurement of acoustic emission (AE) from forming corrosion defects. Criteria of estimating the SCC resistance of the tubes are proposed from measured AE and corrosion damage of the tube material. The results of local SCC tests of cladding tubes of E110 and E635 zirconium alloys are presented.

Rozhnov, A. B.; Belov, V. A.; Nikulin, S. A.; Khanzhin, V. G.

2010-10-01

456

Zirconium-modified materials for selective adsorption and removal of aqueous arsenic  

DOEpatents

A method, composition, and apparatus for removing contaminant species from an aqueous medium comprising: providing a material to which zirconium has been added, the material selected from one or more of zeolites, cation-exchangeable clay minerals, fly ash, mesostructured materials, activated carbons, cellulose acetate, and like porous and/or fibrous materials; and contacting the aqueous medium with the material to which zirconium has been added. The invention operates on all arsenic species in the form of arsenate, arsenite and organometallic arsenic, with no pretreatment necessary (e.g., oxidative conversion of arsenite to arsenate).

Zhao, Hongting; Moore, Robert C.

2004-11-30

457

Normal Zirconium Isotopic Composition in Murchison Hibonite 13-13  

NASA Astrophysics Data System (ADS)

Murchison hibonite 13-13 has a special place in isotopic astronomy because it has the largest isotopic anomalies in Ca and Ti as yet measured with delta ^48Ca at +105 per mil and delta ^50Ti at +273 per mil [1]. It has been suggested that these anomalies are the result of nucleosynthesis in neutron-rich supernova ejecta [2] and Ca and Ti in this hibonite grain have been the least diluted by normal solar system material. It would be expected that the isotopic compositions of the other Fe peak elements would also show the effects of the same nucleosynthetic process(es), but the abundances of the other elements are quite low. This is because of the refractory composition of hibonite and the relatively high volatilities of the other Fe peak elements. Zirconium is another refractory element that has recently been examined for its isotopic composition. Harper and coworkers [3] found a small ^96Zr enhancement (~2 epsilon) in Allende CAIs, and it was suggested that the ^96Zr anomaly was correlated with the ^50Ti enhancements (~10 epsilon) in the same inclusions and that both isotopes were produced by the same process [4]. The purpose of this report is to test whether a ^96Zr anomaly can be resolved in 13-13. If present at the same level as in the Allende CAIs relative to the ^50Ti anomaly, a ^96Zr enhancement of the order of 60 per mil should be observed. Zirconium isotopic compositions were measured by ion microprobe mass spectrometry. A mass resolution of 8000 (1% valley) was found to be sufficient to resolve molecular interferences as well as hydrides. However, in some hibonite analyses, tailing from ^40Ca(sub)2^160^+ became unacceptably large. Terrestrial zircon and Zr metal standards were also measured, and good agreement was found with terrestrial Zr isotopic compositions [5] after normalization to the ^94Zr/^90Zr ratio. The Zr isotopic composition of 13-13 is normal within expenmental uncertainty and the maximum anomaly at the 2- sigma level is well below 10 per mil (Fig. 1). No ^96Zr anomaly is associated with the large ^50Ti anomaly in this Murchison hibonite, and so it is unlikely that the nucleosynthetic model of Harper and coworkers for coproduction of ^96Zr and ^50Ti is valid. References: [1] Ireland T. R. (1990) GCA, 54, 3219-3237. [2] Hartmann D. et al.(1985) Astrophys. J., 297, 837-845. [3] Harper C. L. et al. (1990) Meteoritics, 25, 369. [4] Harper C. L. et al. (1991) LPSC XXII, 517-518. [5] Minster J. and Ricard L. P. (1981) Int. J. Mass Spec. Ion Phys., 37, 259-272. Fig. 1 appears in the hard copy here.

Ireland, T. R.

1993-07-01

458

Ultrasonic texture characterization of aluminum, zirconium and titanium alloys  

SciTech Connect

This work attempts to show the feasibility of nondestructive characterization of non-ferrous alloys. Aluminum alloys have a small single crystal anisotropy which requires very precise ultrasonic velocity measurements for derivation of orientation distribution coefficients (ODCs); the precision in the ultrasonic velocity measurement required for aluminum alloys is much greater than is necessary for iron alloys or other alloys with a large single crystal anisotropy. To provide greater precision, some signal processing corrections need to be applied to account for the inherent, half-bandwidth offset in triggered pulses when using a zero-crossing technique for determining ultrasonic velocity. In addition, alloys with small single crystal anisotropy show a larger dependence on the single crystal elastic constants (SCECs) when predicting ODCs which require absolute velocity measurements. Attempts were made to independently determine these elastics constants in an effort to improve correlation between ultrasonically derived ODCs and diffraction derived ODCs. The greater precision required to accurately derive ODCs in aluminum alloys using ultrasonic nondestructive techniques is easily attainable. Ultrasonically derived ODCs show good correlation with derivations made by Bragg diffraction techniques, both neutron and X-ray. The best correlation was shown when relative velocity measurements could be used in the derivations of the ODCs. Calculation of ODCs in materials with hexagonal crystallites can also be done. Because of the crystallite symmetries, more information can be extracted using ultrasonic techniques, but at a cost of requiring more physical measurements. Some industries which use materials with hexagonal crystallites, e.g. zirconium alloys and titanium, have traditionally used texture parameters which provide some specialized measure of the texture. These texture parameters, called Kearns factors, can be directly related to ODCs.

Anderson, A.J.

1997-10-08

459

Mechanical behaviour of excimer laser irradiated polycrystalline zirconium  

NASA Astrophysics Data System (ADS)

The effects of laser irradiation on the mechanical response of polycrystalline zirconium (Zr) have been investigated. Zr samples were irradiated with an excimer (KrF) laser (? ? 248 nm, ? ? 18 ns and repetition rate ?30 Hz). The irradiation was performed in the ambient environment of a gas mixture containing (CO2:N2:He) under a filling pressure of 20 Torr by varying laser fluences ranging from 3.8 to 5.1 J cm-2. The surface and structural modification of the irradiated targets were investigated using a scanning electron microscope (SEM) and x-ray diffractometer (XRD). In order to explore the mechanical properties of the irradiated Zr, the tensile testing and Vickers microhardness testing techniques were employed. SEM analysis reveals the grain growth on the irradiated Zr surfaces; however, for increasing fluence up to 4.7 J cm-2, the appearance of the grains becomes more distinct with an increase in their number density and decrease in size. For the maximum fluence of 5.1 J cm-2, the grains completely vanish and the surface becomes diffusive. XRD analysis reveals the appearance of new phases of ZrN and ZrO2. The variation in the peak intensity is observed to be anomalous, whereas the decreasing trend in the crystallite size and residual stresses is observed with increasing fluence. The microhardness analysis reveals the increasing trend in surface hardness with increasing fluence. The tensile testing demonstrates the anomalous behaviour of the yield stress and ultimate tensile strength with increasing fluence.

Jelani, Mohsan; Bashir, Shazia; Akram, Mahreen; Yousaf, Daniel; Afzal, Naveed; Ahmad, Sajjad

2014-02-01

460

Assessing the Role of Sewers and Atmospheric Deposition as Nitrate Contamination Sources to Urban Surface Waters using Stable Nitrate Isotopes  

NASA Astrophysics Data System (ADS)

Excess nitrate (NO3-) contributes to the overall degraded quality of streams in many urban areas. These systems are often dominated by impervious surfaces and storm sewers that can route atmospherically deposited nitrogen, from both wet and dry deposition, to waterways. Moreover, in densely populated watersheds there is the potential for interaction between urban waterways and sewer systems. The affects of accumulated nitrate in riverine and estuary systems include low dissolved oxygen, loss of species diversity, increased mortality of aquatic species, and general eutrophication of the waterbody. However, the dynamics of nitrate pollution from each source and it’s affect on urban waterways is poorly constrained. The isotopes of nitrogen and oxygen in nitrate have been proven effective in helping to distinguish contamination sources to ground and surface waters. In order to improve our understanding of urban nitrate pollution sources and dynamics, we examined nitrate isotopes (?15N and ?18O) in base- and stormflow samples collected over a two-year period from a restored urban stream in Pittsburgh, Pennsylvania (USA). Nine Mile Run drains a 1,600 hectare urban watershed characterized by 38% impervious surface cover. Prior work has documented high nitrate export from the watershed (~19 kg NO3- ha-1 yr-1). Potential nitrate sources to the watershed include observed sewer overflows draining directly to the stream, as well as atmospheric deposition (~23 kg NO3- ha-1 yr-1). In this and other urban systems with high percentages of impervious surfaces, there is likely minimal input from nitrate derived from soil or fertilizer. In this presentation, we examine spatial and temporal patterns in nitrate isotopic composition collected at five locations along Nine Mile Run characterized by both sanitary and combined-sewer cross-connections. Preliminary isotopic analysis of low-flow winter streamwater samples suggest nitrate export from Nine Mile Run is primarily influenced by inputs of human waste despite high rates of atmospheric nitrate deposition. Further isotopic analysis of nitrate will examine seasonal variations in nitrate sources; compare nitrate dynamics and sources during low- versus high-flows, and the influence of interannual climatic variability on nitrate export.

Sikora, M. T.; Elliott, E. M.

2009-12-01

461

The atmospheric chemistry of isoprene- and other multifunctional-nitrates  

NASA Astrophysics Data System (ADS)

Formation of alkyl and multifunctional nitrates significantly reduces ozone production rates in their source regions, their transport and subsequent chemistry can impact secondary organic aerosol formation and NOy removal rates and they may lead to the re-release of NOx in regions far-removed from the original source. In this dissertation, the atmospheric chemistry of alkyl and multifunctional nitrates is investigated through a combination of laboratory and field measurements. In contrast to many previous studies that have focused on observations of specific individual nitrate compounds, the work described here uses a technique (Thermal Dissociation-Laser Induced Fluorescence or TD-LIF) that allows for measurements of the sum of all alkyl and multifunctional nitrates. These observations show that alkyl and multifunctional nitrates are a significant fraction of NOy in a number of different chemical regimes representing diverse hydrocarbon mixtures. In what follows, I show that their formation impacts both ozone 1 formation and NOy transport in ways that are not accounted for by currently accepted chemical mechanisms. Aircraft measurements are used to constrain nitrate yields following isoprene oxidation by OH, the atmospheric lifetimes of these nitrates, and the retention rate of the nitrate functional group upon oxidation of the initial isoprene nitrates. It is found that nitrate functionality is maintained upon further oxidation at least 75% of the time indicating that the lifetime of isoprene nitrates as a pool of compounds is considerably longer than the lifetime of the individual isoprene nitrates with respect to reaction with OH. We examine the products of NO3-initiated oxidation of isoprene in a smog-chamber, propose a detailed reaction scheme, and find that nitrates are produced with a yield of 65+/-12%, the majority of which are carbonyl nitrates. We investigate the role of alkyl and multifunctional nitrates in the Mexico City plume where they are observed to be more abundant than expected given currently accepted chemical mechanisms. We investigate several possible explanations for the unexpectedly high abundances and calculate that their formation depresses ozone production in the near-field of Mexico City by as much as 30%.

Perring, Anne Elizabeth

462

A modified procedure for measuring oxygen-18 content of nitrate  

NASA Astrophysics Data System (ADS)

SummaryMass spectrometric analysis of O-isotopic composition of nitrate has many potential applications in studies of environmental processes. Through this work, rapid, reliable, precise, broadly applicable, catalyst-free, low-priced and less labor intensive procedure for measuring ?18O of nitrate using Isotope Ratio Mass Spectrometer has been developed and implemented. The conditions necessary to effect complete nitrate recovery and complete removal of other oxygen containing anions and dissolved organic carbon (DOC) without scarifying the isotopic signature of nitrate were investigated. The developed procedure consists of two main parts: (1) wet chemistry train for extraction and purification of nitrate from the liquid matrix; (2) off-line pyrolysis of extracted nitrate salt with activated graphite at 550 °C for 30 min. The conditions necessary to effect complete nitrate recovery and complete removal of other oxygen containing compounds were investigated. Dramatic reduction in processing times needed for analysis of ?18O of nitrate at natural abundance level was achieved. Preservation experiments revealed that chloroform (99.8%) is an effective preservative. Isotopic contents of some selected nitrate salts were measured using the modified procedure and some other well established methods at two laboratories in Egypt and Germany. Performance assessment of the whole developed analytical train was made using internationally distributed nitrate isotopes reference materials and real world sample of initial zero-nitrate content. The uncertainty budget was evaluated using the graphical nested hierarchal approach. The obtained results proved the suitability for handling samples of complicated matrices. Reduction of consumables cost by about 80% was achieved.

Ahmed, M. A.; Aly, A. I. M.; Abdel Monem, N.; Hanafy, M.; Gomaa, H. E.

2012-11-01

463

Corrosion of aluminides by molten nitrate salt  

SciTech Connect

The corrosion of titanium-, iron-, and nickel-based aluminides by a highly aggressive, oxidizing NaNO{sub 3}(-KNO{sub 3})-Na{sub 2}O{sub 2} has been studied at 650{degree}C. It was shown that weight changes could be used to effectively evaluate corrosion behavior in the subject nitrate salt environments provided these data were combined with salt analyses and microstructural examinations. The studies indicated that the corrosion of relatively resistant aluminides by these nitrate salts proceeded by oxidation and a slow release from an aluminum-rich product layer into the salt at rates lower than that associated with many other types of metallic materials. The overall corrosion process and resulting rate depended on the particular aluminide being exposed. In order to minimize corrosion of nickel or iron aluminides, it was necessary to have aluminum concentrations in excess of 30 at. %. However, even at a concentration of 50 at. % Al, the corrosion resistance of TiAl was inferior to that of Ni{sub 3}Al and Fe{sub 3}Al. At higher aluminum concentrations, iron, nickel, and iron-nickel aluminides exhibited quite similar weight changes, indicative of the principal role of aluminum in controlling the corrosion process in NaNO{sub 3}(-KNO{sub 3})-Na{sub 2}O{sub 2} salts. 20 refs., 5 figs., 3 tabs.

Tortorelli, P.F.; Bishop, P.S.

1990-01-01

464

Electrochemical processing of nitrate waste solutions  

SciTech Connect

The second phase of research performed at The Electrosynthesis Co., Inc. has demonstrated the successful removal of nitrite and nitrate from a synthetic effluent stream via a direct electrochemical reduction at a cathode. It was shown that direct reduction occurs at good current efficiencies in 1,000 hour studies. The membrane separation process is not readily achievable for the removal of nitrites and nitrates due to poor current efficiencies and membrane stability problems. A direct reduction process was studied at various cathode materials in a flow cell using the complete synthetic mix. Lead was found to be the cathode material of choice, displaying good current efficiencies and stability in short and long term tests under conditions of high temperature and high current density. Several anode materials were studied in both undivided and divided cell configurations. A divided cell configuration was preferable because it would prevent re-oxidation of nitrite by the anode. The technical objective of eliminating electrode fouling and solids formation was achieved although anode materials which had demonstrated good stability in short term divided cell tests corroded in 1,000 hour experiments. The cause for corrosion is thought to be F[sup [minus

Genders, D.; Weinberg, N.; Hartsough, D. (Electrosynthesis Co., Inc., Cheektowaga, NY (United States))

1992-10-07

465

Effect of nitrate ions on the oxidation of iodide ions during the dissolution of ?-irradiated NaCl in aqueous binary mixture of iodide and nitrate  

Microsoft Academic Search

It is now well established that the oxidation of iodide ions and the reduction of nitrate ions take place when -irradiated sodium chloride is dissolved in aqueous iodide and nitrate solutions, respectively. The yield of iodine decreases and that of nitrite increases with increasing concentration of nitrate in a binary mixture of iodide and nitrate when the irradiated salt is

C. D. Kalkar; S. V. Doshi

1988-01-01

466

78 FR 35258 - Solid Agricultural Grade Ammonium Nitrate from Ukraine: Continuation of Antidumping Duty Order  

Federal Register 2010, 2011, 2012, 2013, 2014

...Trade Administration [A-823-810] Solid Agricultural Grade Ammonium Nitrate from...of the antidumping duty order \\1\\ on solid agricultural grade ammonium nitrate from...1\\ See Antidumping Duty Order: Solid Agricultural Grade Ammonium Nitrate...

2013-06-12

467

40 CFR 415.530 - Applicability; description of the silver nitrate production subcategory.  

Code of Federal Regulations, 2010 CFR

...true Applicability; description of the silver nitrate production subcategory. 415...CHEMICALS MANUFACTURING POINT SOURCE CATEGORY Silver Nitrate Production Subcategory § 415.530 Applicability; description of the silver nitrate production subcategory....

2010-07-01

468

76 FR 49449 - Continuation of Antidumping Duty Order on Solid Fertilizer Grade Ammonium Nitrate From the...  

Federal Register 2010, 2011, 2012, 2013, 2014

...Fertilizer Grade Ammonium Nitrate From the Russian Federation AGENCY: Import Administration...ammonium nitrate'') from the Russian Federation (``Russia'') would likely...Fertilizer Grade Ammonium Nitrate From the Russian Federation and Notice of Antidumping...

2011-08-10

469

76 FR 39847 - Solid Fertilizer Grade Ammonium Nitrate From the Russian Federation; Final Results of the...  

Federal Register 2010, 2011, 2012, 2013, 2014

...Fertilizer Grade Ammonium Nitrate From the Russian Federation; Final Results of the Expedited...ammonium nitrate'') from the Russian Federation (``Russia'').\\1...Fertilizer Grade Ammonium Nitrate From the Russian Federation, 64 FR 45236 (August...

2011-07-07

470

21 CFR 172.167 - Silver nitrate and hydrogen peroxide solution.  

Code of Federal Regulations, 2010 CFR

... true Silver nitrate and hydrogen peroxide solution. 172.167 Section...172.167 Silver nitrate and hydrogen peroxide solution. An aqueous solution...mixture of silver nitrate and hydrogen peroxide may be safely used in...

2010-04-01

471

21 CFR 172.167 - Silver nitrate and hydrogen peroxide solution.  

Code of Federal Regulations, 2011 CFR

... false Silver nitrate and hydrogen peroxide solution. 172.167 Section...172.167 Silver nitrate and hydrogen peroxide solution. An aqueous solution...mixture of silver nitrate and hydrogen peroxide may be safely used in...

2011-04-01

472

21 CFR 172.167 - Silver nitrate and hydrogen peroxide solution.  

Code of Federal Regulations, 2014 CFR

... false Silver nitrate and hydrogen peroxide solution. 172.167 Section...172.167 Silver nitrate and hydrogen peroxide solution. An aqueous solution...mixture of silver nitrate and hydrogen peroxide may be safely used in...

2014-04-01

473

21 CFR 172.167 - Silver nitrate and hydrogen peroxide solution.  

Code of Federal Regulations, 2012 CFR

... false Silver nitrate and hydrogen peroxide solution. 172.167 Section...172.167 Silver nitrate and hydrogen peroxide solution. An aqueous solution...mixture of silver nitrate and hydrogen peroxide may be safely used in...

2012-04-01

474

21 CFR 172.167 - Silver nitrate and hydrogen peroxide solution.  

Code of Federal Regulations, 2013 CFR

... false Silver nitrate and hydrogen peroxide solution. 172.167 Section...172.167 Silver nitrate and hydrogen peroxide solution. An aqueous solution...mixture of silver nitrate and hydrogen peroxide may be safely used in...

2013-04-01

475

Royal Swedish Academy of Sciences Assessing Groundwater Nitrate Contamination for Resource and Landscape Management  

E-print Network

Groundwater nitrate concentrations increased and some- times exceeded public health standards during the last nitrate concentration increased where excess nitrogen loads in soils were greatest, soils rated highestRoyal Swedish Academy of Sciences Assessing Groundwater Nitrate Contamination for Resource

Zhang, Minghua

476

Effects of arsenic on nitrate metabolism in arsenic hyperaccumulating and non-hyperaccumulating ferns  

E-print Network

Effects of arsenic on nitrate metabolism in arsenic hyperaccumulating and non Arsenic reduced the activity of nitrate and nitrite reductase more in Pteris ensiformis than Pteris March 2009 Accepted 26 March 2009 Keywords: Arsenic Nitrate metabolism Pteris vittata Arsenic

Ma, Lena

477

40 CFR 418.40 - Applicability; description of the ammonium nitrate subcategory.  

Code of Federal Regulations, 2010 CFR

...description of the ammonium nitrate subcategory. The provisions...the manufacture of ammonium nitrate. Discharges attributable...battery limits of the ammonium nitrate manufacturing operations...306(b), Federal Water Pollution Control Act, as...

2010-07-01

478

VOCs, Pesticides, Nitrate, and Their Mixtures in Groundwater Used for  

E-print Network

VOCs, Pesticides, Nitrate, and Their Mixtures in Groundwater Used for Drinking Water in the United areas. For each sample, as many as 60 volatile organic compounds (VOCs), 83 pesticides, and nitrate were to have an anthropogenic origin. VOCs were detected more frequently (44%) than pesticides (38

479

Nitrate formation in acid forest soils from the Adirondacks  

SciTech Connect

Nitrate formation in three forest soils from the Adirondacks region of New York was studied in the laboratory. The organic and surface mineral layers of the soils has pH values ranging from 3.6 to 4.1. Nitrate was formed when the soils were treated with artificial rain at pH 3.5, 4.1, or 5.6. Compared to simulated rain at pH 5.6, simulated rain at pH 3.5 enhanced nitrate formation in one soil and inhibited it in two other soils. The rate of nitrate accumulation was about 10 times higher in the organic horizon than in the mineral horizon, and nitrate formation was not enhanced by ammonium additions. Nitrate formation in soil suspensions was dependent on the amount of soil in the suspension, and none was formed if little soil was present. Ammonium did not enhance nitrate production in the suspensions. It is suggested that nitrate formation in these acid soils is not limited by the ammonium supply. 19 references, 2 figures, 2 tables.

Klein, T.M.; Kreitinger, J.P.; Alexander, M.

1983-01-01

480

NITRATE REMOVAL FROM WATER SUPPLIES BY ION EXCHANGE - EXECUTIVE SUMMARY  

EPA Science Inventory

Anion exchange using synthetic organic resins is a proven and practical technology for the removal of nitrate from water supplies. However, disposal of the spent regenerant brime solution containing nitrate is a potential problem. Two processes were examined in detail in this rep...

481

Method for improved decomposition of metal nitrate solutions  

DOEpatents

A method for co-conversion of aqueous solutions of one or more heavy metal nitrates is described, wherein thermal decomposition within a temperature range of about 300 to 800/sup 0/C is carried out in the presence of about 50 to 500% molar concentration of ammonium nitrate to total metal.

Haas, P.A.; Stines, W.B.

1981-01-21

482

Molybdenum and Iron Requirements for Nitrate Reductase in Photobacterium sepia  

Microsoft Academic Search

Sadana and McElroy1 showed that nitrate reductase from, the halophytic bacterium, Achromobacter fischeri, required iron for its activity, but a deficiency of other micronutrients including molybdenum did not appear to affeot the enzyme. In addition, they found that the bacterium would not grow with nitrate as the sole nitrogen source. We now report that this bacterium (kindly supplied by Dr.

D. J. D. Nicholas; W. J. Redmond; M. A. Wright

1963-01-01

483

Thorium Nitrate Stockpile--From Here to Eternity  

Microsoft Academic Search

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 million lb) of thorium nitrate crystals (hydrate form) stored at two depot locations in the United States. DNSC

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

2003-01-01

484

Potential Radon222 Emissions from the Thorium Nitrate Stockpile  

Microsoft Academic Search

The Defense National Stockpile Center (DNSC), a field level activity of the Defense Logistics Agency, has stewardship of a stockpile of thorium nitrate that has been in storage for decades. The thorium nitrate stockpile was produced from 1959 to 1964 for the Atomic Energy Commission and previously has been under the control of several federal agencies. The stockpile consists of

2003-01-01

485

SULFATE AND NITRATE COATINGS ON MINERAL DUSTS: CRYSTALLINE OR AQUEOUS?  

E-print Network

02138, USA Keywords: Phase transition; Atmospheric Aerosols; Ammonium sulfate; Ammonium nitrate and are in aqueous form. For example, the deliquescence relative humidity of ammonium sulfate is 80% at 298 K while relative humidity; D = diameter (nm) of mineral core particle; AS = ammonium sulfate; AN = ammonium nitrate

486

Research Indicates Sprinkler Irrigation Use Could Reduce Groundwater Nitrate Levels  

E-print Network

researcher said. "The U.S. Environmental Protection Agency's safe drinking water standard for nitrates is 10 averaging 30 ppm, three times the EPA's safe drinking water limit. Nitrate levels were generally highest of irrigation systems on three corn test fields near Shelton, Neb., leave little doubt that if more center pivot

Nebraska-Lincoln, University of

487

Phytoremediation of Nitrate-Contaminated Groundwater by Desert Phreatophytes  

Microsoft Academic Search

Two native halophytic shrubs were evaluated for phytoremediation of a nitrate- contaminated aquifer at a former uranium mill site. The shrubs, Sarcobatus vermiculatus and Atriplex canescens, obligate and facultative phreatophytes, respectively, dominate the desert plant community. Stable isotope signatures suggested that both species are rooted into the nitrate plume, a depth averaging more than 10 meters. Aerial photography and ground

Casey McKeon; Edward P. Glenn; David Moore; W. Jody Waugh

488

Spatial assessment of animal manure spreading and groundwater nitrate pollution.  

PubMed

Nitrate concentration in groundwater has frequently been linked to non-point pollution. At the same time the existence of intensive agriculture and extremely intensive livestock activity increases the potential for nitrate pollution in shallow groundwater. Nitrate used in agriculture could cause adverse effects on human and animal health. In order to evaluate the groundwater nitrate pollution, and how it might evolve in time, it is essential to develop control systems and to improve policies and incentives aimed at controlling the amount of nitrate entering downstream water systems. The province of Caserta in southern Italy is characterized by high levels of animal manure loading. A comparison between manure nitrogen production and nitrate concentration in groundwater was carried out in this area, using geostatistical tools and spatial statistics. The results show a discrepancy between modelling of nitrate leaching and monitoring of the groundwater and, moreover, no spatial correlation between nitrogen production in livestock farms and nitrate concentration in groundwater, suggesting that producers are not following the regulatory procedures for the agronomic use of manure. The methodology developed in this paper could be applied also in other regions in which European Union fertilization plans are not adequately followed. PMID:19908188

Infascelli, Roberta; Pelorosso, Raffaele; Boccia, Lorenzo

2009-11-01

489

Proposed nitrate binding by hemoglobin in Riftia pachyptila blood  

NASA Astrophysics Data System (ADS)

Riftia pachyptila lives in the unstable environment at hydrothermal vent sites along oceanic spreading zones in the Eastern Pacific. The tubeworm has a symbiosis with intracellular carbon-fixing and sulfide-oxidizing bacteria. Nitrate is the main source of nitrogen available from their habitat. This compound serves as a substrate either for nitrate respiration or for biosynthesis after transformation into ammonia. Very high nitrate (up to 3.2 mM) and nitrite (up to 0.8 mM) concentrations in vascular blood of R. pachyptila indicate a novel uptake mechanism. The dialysis experiments reported here demonstrate the binding and transport of nitrate to the symbionts by high molecular weight components in the blood, most likely hemoglobin. The extent to which nitrate is bound differed markedly between blood from different animals. In addition, a strong inverse correlation was found between the concentrations of sulfide and nitrate in vascular blood, as well as between the sulfur content of trophosome and the nitrate content of vascular blood. Specimens with low sulfur stores showed much lower nitrate levels than those with pale green trophosome due to high levels of elemental sulfur.

Hahlbeck, Edda; Pospesel, Mark A.; Zal, Franck; Childress, James J.; Felbeck, Horst

2005-10-01

490

Nitrate Water Activities, Science Study Aid No. 4.  

ERIC Educational Resources Information Center

Intended to supplement a regular program, this pamphlet provides background information, related activities, and suggestions for other activities on the subject of nitrate as a water pollutant. Two activities related to plant nutrient pollution, nitrate filtration and measuring mitrate used by plants, are explained in detail, outlining objectives,…

Agricultural Research Service (USDA), Washington, DC.

491

Reversible inactivation of nitrate reductase in Chlorella vulgaris in vivo  

Microsoft Academic Search

The NADH-nitrate oxidoreductase of Chlorella vulgaris has an inactive form which has previously been shown to be a cyanide complex of the reduced enzyme. This inactive enzyme can be reactivated by treatment with ferricyanide in vitro. In the present study, the activation state of the enzyme was determined after different prior in vivo programs involving environmental variations. Oxygen, nitrate, light

Elfriede K. Pistorius; Hans-Siegfried Gewitz; Helga Voss; Birgit Vennesland

1976-01-01

492

Nitrate leaching as influenced by soil tillage and catch crop  

Microsoft Academic Search

Because of public and political concern for the quality of surface and ground water, leaching of nitrate is of special concern in many countries. To evaluate the effects of tillage and growth of a catch crop on nitrate leaching, two field trials were conducted in spring barley (Hordeum vulgare L.) under temperate coastal climate conditions. On a coarse sand (1987–1992),

E. Møller Hansen; J. Djurhuus

1997-01-01

493