Airborne Precursors Predict Maternal Serum Perfluoroalkyl Acid Concentrations.

Science.gov (United States)

Makey, Colleen M; Webster, Thomas F; Martin, Jonathan W; Shoeib, Mahiba; Harner, Tom; Dix-Cooper, Linda; Webster, Glenys M

2017-07-05

Human exposure to persistent perfluoroalkyl acids (PFAAs), including perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), and perfluorooctanesulfonate (PFOS), can occur directly from contaminated food, water, air, and dust. However, precursors to PFAAs (PreFAAs), such as dipolyfluoroalkyl phosphates (diPAPs), fluorotelomer alcohols (FTOHs), perfluorooctyl sulfonamides (FOSAs), and sulfonamidoethanols (FOSEs), which can be biotransformed to PFAAs, may also be a source of exposure. PFAAs were analyzed in 50 maternal sera samples collected in 2007-2008 from participants in Vancouver, Canada, while PFAAs and PreFAAs were measured in matching samples of residential bedroom air collected by passive sampler and in sieved vacuum dust (<150 μm). Concentrations of PreFAAs were higher than for PFAAs in air and dust. Positive associations were discovered between airborne 10:2 FTOH and serum PFOA and PFNA and between airborne MeFOSE and serum PFOS. On average, serum PFOS concentrations were 2.3 ng/mL (95%CI: 0.40, 4.3) higher in participants with airborne MeFOSE concentrations in the highest tertile relative to the lowest tertile. Among all PFAAs, only PFNA in air and vacuum dust predicted serum PFNA. Results suggest that airborne PFAA precursors were a source of PFOA, PFNA, and PFOS exposure in this population.

Acid precipitation; an annotated bibliography

Science.gov (United States)

Wiltshire, Denise A.; Evans, Margaret L.

1984-01-01

This collection of 1660 bibliographies references on the causes and environmental effects of acidic atmospheric deposition was compiled from computerized literature searches of earth-science and chemistry data bases. Categories of information are (1) atmospheric chemistry (gases and aerosols), (2) precipitation chemistry, (3) transport and deposition (wet and dry), (4) aquatic environments (biological and hydrological), (5) terrestrial environments, (6) effects on materials and structures, (7) air and precipitation monitoring and data collection, and (8) modeling studies. References date from the late 1800 's through December 1981. The bibliography includes short summaries of most documents. Omitted are unpublished manuscripts, publications in press, master 's theses and doctoral dissertations, newspaper articles, and book reviews. Coauthors and subject indexes are included. (USGS)

Acid precipitation and forest vegetation

Energy Technology Data Exchange (ETDEWEB)

Tamm, C O; Cowling, E B

1977-04-01

Effects of acidic precipitation on forest vegetation may be classified as being either direct or indirect. Among the most important direct effects are damage to protective cuticular layers, interference with normal functioning of guard cells, poisoning of plant cells after diffusion of acidic substances through stomata or cuticle and interference with reproductive processes. Indirect effects include accelerated leaching of substances from foliar organs, increased susceptibility to drought and other environmental stress factors, and alteration of symbiotic associations and host-parasite interactions. The potential importance of nutrient uptake through foliage and the need to understand atmosphere-plant-soil interactions are stressed.

Perfluoroalkyl acids and their precursors in Swedish food: The relative importance of direct and indirect dietary exposure

International Nuclear Information System (INIS)

Gebbink, Wouter A.; Glynn, Anders; Darnerud, Per Ola; Berger, Urs

2015-01-01

We analyzed food market basket samples obtained in Sweden from 1999, 2005, and 2010 for perfluoroalkyl acids (PFAAs) and a range of precursor compounds. Perfluorooctane sulfonic acid (PFOS) precursors were detected in all food year pools with the highest concentrations in 1999. Six polyfluoroalkyl phosphate diesters (diPAPs, 4:2/6:2, 6:2/6:2, 6:2/8:2, 8:2/8:2, 6:2/10:2, and 10:2/10:2) were detected in the year pools with the highest ∑diPAP concentrations in 1999 and 2005. All precursors were predominantly found in meat, fish, and/or eggs based on analysis of individual food groups from 1999. Based on year pools, PFOS precursors contributed between 4 and 1% as an indirect source to total dietary PFOS intakes between 1999 and 2010. Perfluorohexanoic acid (PFHxA) exposure originated entirely from diPAPs, whereas for perfluorooctanoic acid (PFOA) and perfluorodecanoic acid (PFDA), diPAPs contributed between 1 and 19% to total exposure. The lowest precursor contributions were generally seen in food samples from 2010. - Highlights: • Three PFOS precursors and six diPAPs were detected in food pools. • Precursor concentrations were highest in 1999 and 2005 food pools, and lowest in 2010. • The relative importance of precursors to total PFOS dietary intake was <4%. • The relative importance of diPAPs as an indirect dietary source of PFCAs was chain length dependent. - The relative contribution of precursors to PFOS dietary intakes is small, whereas the contribution of diPAPs to PFCA dietary intakes varies with the PFCA chain length

Impact of acid precipitation on recreation and tourism in Ontario: an overview

Energy Technology Data Exchange (ETDEWEB)

1984-01-01

The impacts of acid precipitation on fishing opportunities, waterfowl and moose hunting, water contact activities, and the perception of the environment in Ontario are analyzed. Economic effects and future research needs are also estimated and discussed. These questions have been examined by identifying the likely links between acidic precipitation and recreation and tourism, by developing estimates of the importance of aquatic-based recreation and tourism, by describing the current and estimated future effects of acid precipitation. 101 references, 9 figures, 19 tables.

Characteristics of a continuous denitration by formic acid - electrolytic trimming of residual acid with accompanying the precipitation of metal ions

International Nuclear Information System (INIS)

Kim, G. W.; Kim, S. H.; Lim, J. G.; Lee, I. H.

2003-01-01

This work has studied the characteristics of destruction of nitric acid and precipitation of several metal ions in a continuous denitration process combining a denitration by formic acid and a residual acid-electrolytic trimming system. The metal ions of Zr, Mo, Fe, and Nd did not affect the electrodes at the step of electrolytic trimming of the residual acid after denitration by formic acid. The Mo ion in electrolytic solution enhanced the generation of nitrite ion during the electrolytic reaction. The mole ratio of formic acid to nitric acid fed into the continuous denitration reactor using formic acid affected much the final acidity, the precipitation yields of metal ions, the precipitate morphology. At the ratio of 1.65, the process had the lowest final acidity of less than 0.1 M, and the precipitation yields of Zr and Mo reached 95% and 83%, respectively as the highest values

Indium sulfide precipitation from hydrochloric acid solutions of calcium and sodium chlorides

International Nuclear Information System (INIS)

Kochetkova, N.V.; Bayandina, Yu.E.; Toptygina, G.M.; Shepot'ko, A.O.

1988-01-01

The effect of precipitation duration, acid concentration, indium complexing with chloride ions on the process of indium sulfide chemical precipitation in hydrochloric acid solutions, precipitate composition and dispersity are studied. It is established that indium sulfide solubility increases in solutions with acid concentration exceeding 0.40-0.45 mol/l. Calcium and indium chloride addition to diluted hydrochloric solutions greatly increases the solubility of indium sulfide. The effect of calcium chloride on In 2 S 3 solubility is higher than that of sodium chloride

Acid Precipitation Awareness Curriculum Materials in the Life Sciences.

Science.gov (United States)

Stubbs, Harriett S.

1983-01-01

Provides an outline of course content for acid precipitation and two acid rain activities (introduction to pH and effects of acid rain on an organism). Information for obtaining 20 additional activities as well as an information packet containing booklets, pamphlets, and articles are also provided. (JN)

Estimating of precursors and behavior of acid precipitation wet and dry, in the north of Bogota

International Nuclear Information System (INIS)

Garcia Lozada, Hector; Natal, Angelica; Esquivel, Antolinez; Diaz Alvarez, Cristian Julian

2004-01-01

Measurements of pH of the wet deposition were made in the north sector of Bogota, in two manual stations located to the East (Sans Facon) and to the West (Agustiniano Norte) of the northern highway, which served as the axis of the studied area, with an approximated extension of 54 km 2 . By means of an algorithm based on the model CORINAIR, the emissions of the precursors of acid rain were obtained: NOx (7665 T/y) and SO 2 (109 T/y). Between December 2002 and April 2003, 35 rain events were evaluated and it was found that 70% of the 17 rain water samples in the eastern sector and 83% of the 18 ones in the western sector, as viewed from the northern highway, show a pH smaller than 5.6, considered to be the natural value of the pH in rain. In the settled dust, to the west of the highway, the pH reached a value of 7.47, that to the east reached 7.78, while along monitoring lines the pH ranged between 5.71 and 6.70

From iron(III) precursor to magnetite and vice versa

International Nuclear Information System (INIS)

Gotic, M.; Jurkin, T.; Music, S.

2009-01-01

The syntheses of nanosize magnetite particles by wet-chemical oxidation of Fe 2+ have been extensively investigated. In the present investigation the nanosize magnetite particles were synthesised without using the Fe(II) precursor. This was achieved by γ-irradiation of water-in-oil microemulsion containing only the Fe(III) precursor. The corresponding phase transformations were monitored. Microemulsions (pH ∼ 12.5) were γ-irradiated at a relatively high dose rate of ∼22 kGy/h. Upon 1 h of γ-irradiation the XRD pattern of the precipitate showed goethite and unidentified low-intensity peaks. Upon 6 h of γ-irradiation, reductive conditions were achieved and substoichiometric magnetite (∼Fe 2.71 O 4 ) particles with insignificant amount of goethite particles found in the precipitate. Hydrated electrons (e aq - ), organic radicals and hydrogen gas as radiolytic products were responsible for the reductive dissolution of iron oxide in the microemulsion and the reduction Fe 3+ → Fe 2+ . Upon 18 h of γ-irradiation the precipitate exhibited dual behaviour, it was a more oxidised product than the precipitate obtained after 6 h of γ-irradiation, but it contained magnetite particles in a more reduced form (∼Fe 2.93 O 4 ). It was presumed that the reduction and oxidation processes existed as concurrent competitive processes in the microemulsion. After 18 h of γ-irradiation the pH of the medium shifted from the alkaline to the acidic range. The high dose rate of ∼22 kGy/h was directly responsible for this shift to the acidic range. At a slightly acidic pH a further reduction of Fe 3+ → Fe 2+ resulted in the formation of more stoichiometric magnetite particles, whereas the oxidation conditions in the acidic medium permitted the oxidation Fe 2+ → Fe 3+ . The Fe 3+ was much less soluble in the acidic medium and it hydrolysed and recrystallised as goethite. The γ-irradiation of the microemulsion for 25 h at a lower dose rate of 16 kGy/h produced pure

Perfluoroalkyl acids and their precursors in Swedish food: The relative importance of direct and indirect dietary exposure.

Science.gov (United States)

Gebbink, Wouter A; Glynn, Anders; Darnerud, Per Ola; Berger, Urs

2015-03-01

We analyzed food market basket samples obtained in Sweden from 1999, 2005, and 2010 for perfluoroalkyl acids (PFAAs) and a range of precursor compounds. Perfluorooctane sulfonic acid (PFOS) precursors were detected in all food year pools with the highest concentrations in 1999. Six polyfluoroalkyl phosphate diesters (diPAPs, 4:2/6:2, 6:2/6:2, 6:2/8:2, 8:2/8:2, 6:2/10:2, and 10:2/10:2) were detected in the year pools with the highest ∑diPAP concentrations in 1999 and 2005. All precursors were predominantly found in meat, fish, and/or eggs based on analysis of individual food groups from 1999. Based on year pools, PFOS precursors contributed between 4 and 1% as an indirect source to total dietary PFOS intakes between 1999 and 2010. Perfluorohexanoic acid (PFHxA) exposure originated entirely from diPAPs, whereas for perfluorooctanoic acid (PFOA) and perfluorodecanoic acid (PFDA), diPAPs contributed between 1 and 19% to total exposure. The lowest precursor contributions were generally seen in food samples from 2010. Copyright © 2014 The Authors. Published by Elsevier Ltd.. All rights reserved.

Tracing of salicylic acid additive during precipitation of zirconium

International Nuclear Information System (INIS)

Bharati Misra, U.; Gopala Krishna, K.; Narasimha Murty, B.; Yadav, R.B.

2011-01-01

This paper presents the results of experimental study carried out to know whether the salicylic acid used as an additive during the precipitation of zirconium using ammonium hydroxide solution goes into the filtrate, remains in the hydrated zirconia or gets distributed between the both under the ambient conditions of precipitation. Keeping its simplicity and amenability to adopt on a routine basis, spectrophotometric method has been chosen for the purpose among the many methods available and the problems associated in determining salicylic acid in the presence of zirconium and the medial measures to circumvent the same have been brought out in detail. (author)

Precipitation stripping of neodymium from carboxylate extractant with aqueous oxalic acid solutions

International Nuclear Information System (INIS)

Konishi, Yasuhiro; Asai, Satoru; Murai, Tetuya

1993-01-01

This paper describes a precipitation stripping method in which neodymium ions are stripped from carboxylate extractant in organic solvent and simultaneously precipitated with aqueous oxalic acid solution. For the single-stage process, a quantitative criterion for precipitating oxalate powders was derived theoretically, and stripping experiments were done under the precipitation conditions. The resultant precipitates were neodymium oxalate, which is completely free from contamination by the carboxylate extractant and the organic solvent. The overall rate of stripping was controlled by the transfer of neodymium carboxylate in the organic solution, indicating that the presence of oxalic acid in the aqueous phase has no effect on the stripping rate. These findings demonstrate the feasibility of combining the conventional stripping and precipitation stages in a solvent extraction process for separation and purification of rare earths

Polymethacrylic acid as a new precursor of CuO nanoparticles

Science.gov (United States)

Hosny, Nasser Mohammed; Zoromba, Mohamed Shafick

2012-11-01

Polymethacrylic acid and its copper complexes have been synthesized and characterized. These complexes have been used as precursors to produce CuO nanoparticles by thermal decomposition in air. The stages of decompositions and the calcination temperature of the precursors have been determined from thermal analyses (TGA). The obtained CuO nanoparticles have been characterized by X-ray diffraction (XRD), scanning tunneling microscopy (STM) and transmission electron microscopy (TEM). XRD showed a monoclinic structure with particle size 8-20 nm for the synthesized copper oxide nanoparticles. These nanoparticles are catalytically active in decomposing hydrogen peroxide and a mechanism of decomposition has been suggested.

Acidic precipitation, Vol. 1: Case studies. Advances in environmental science

Energy Technology Data Exchange (ETDEWEB)

Adriano, D.C.; Havas, M. (eds.)

1989-01-01

As has been the case with many environmental issues of the twentieth century, acidic precipitation has its origin in emissions to the atmosphere of numerous compounds from both natural and man-made sources. This volume of the subseries Acidic precipitation emphasizes some of the classical interactions between acidic deposition and ecological effects. It covers the cycling, behavior, and effects of acidic components in nature. Included are the effects of acidic deposition on soil chemistry, soil solution chemistry, aquatic chemistry, forest productivity, and fish populations. Several major ecological consequences, such as a decline in forest productivity, soil and water acidification, depletion of fish populations, and slower litter decomposition are highlighted. A chapter is devoted to the comparative biogeochemistry of aluminum, encompassing several ecosystems in North America and Europe. Nine chapters have been processed separately for inclusion in the appropriate data bases.

Wet precipitators for sulphuric acid plants

International Nuclear Information System (INIS)

Ojanpera, R.O.

1989-01-01

Both the service requirements and design construction details have changed considerably in recent years for wet electrostatic precipitators as used for gas cleaning ahead of metallurgical sulphuric acid plants. Increased concern over acid quality has resulted in more emphasis on dust efficiencies compared to collection of acid mist. Also, higher static operating pressures have caused large structural loads on casing and internal components. In this paper these two issues are addressed in the following ways: Recognition that all dusts do not collect similarly. The mechanism by which various dusts collect affect the design of the entire wet gas cleaning system. Use of both traditional and newer materials of construction to accommodate the higher design pressures while still maintaining corrosion resistance

Arsenic removal from acidic solutions with biogenic ferric precipitates

Energy Technology Data Exchange (ETDEWEB)

Ahoranta, Sarita H., E-mail: sarita.ahoranta@tut.fi [Department of Chemistry and Bioengineering, Tampere University of Technology, P.O. Box 541, FI-33101 Tampere (Finland); Kokko, Marika E., E-mail: marika.kokko@tut.fi [Department of Chemistry and Bioengineering, Tampere University of Technology, P.O. Box 541, FI-33101 Tampere (Finland); Papirio, Stefano, E-mail: stefano.papirio@unicas.it [Department of Chemistry and Bioengineering, Tampere University of Technology, P.O. Box 541, FI-33101 Tampere (Finland); Özkaya, Bestamin, E-mail: bozkaya@yildiz.edu.tr [Department of Chemistry and Bioengineering, Tampere University of Technology, P.O. Box 541, FI-33101 Tampere (Finland); Department of Environmental Engineering, Yildiz Technical University, Davutpasa Campus 34220, Esenler, Istanbul (Turkey); Puhakka, Jaakko A., E-mail: jaakko.puhakka@tut.fi [Department of Chemistry and Bioengineering, Tampere University of Technology, P.O. Box 541, FI-33101 Tampere (Finland)

2016-04-05

Highlights: • Continuous and rapid arsenic removal with biogenic jarosite was achieved at pH 3.0. • Arsenic removal was inefficient below pH 2.4 due to reduced Fe–As co-precipitation. • As(V) had better sorption characteristics than As(III). • Biogenic jarosite adsorbed arsenic more effectively than synthetic jarosite. - Abstract: Treatment of acidic solution containing 5 g/L of Fe(II) and 10 mg/L of As(III) was studied in a system consisting of a biological fluidized-bed reactor (FBR) for iron oxidation, and a gravity settler for iron precipitation and separation of the ferric precipitates. At pH 3.0 and FBR retention time of 5.7 h, 96–98% of the added Fe(II) precipitated (99.1% of which was jarosite). The highest iron oxidation and precipitation rates were 1070 and 28 mg/L/h, respectively, and were achieved at pH 3.0. Subsequently, the effect of pH on arsenic removal through sorption and/or co-precipitation was examined by gradually decreasing solution pH from 3.0 to 1.6 (feed pH). At pH 3.0, 2.4 and 1.6, the highest arsenic removal efficiencies obtained were 99.5%, 80.1% and 7.1%, respectively. As the system had ferric precipitates in excess, decreased arsenic removal was likely due to reduced co-precipitation at pH < 2.4. As(III) was partially oxidized to As(V) in the system. In shake flask experiments, As(V) sorbed onto jarosite better than As(III). Moreover, the sorption capacity of biogenic jarosite was significantly higher than that of synthetic jarosite. The developed bioprocess simultaneously and efficiently removes iron and arsenic from acidic solutions, indicating potential for mining wastewater treatment.

The effect of acid precipitation on tree growth in eastern North America

Science.gov (United States)

Charles V. Cogbill

1976-01-01

Detailed study of the history of forest tree growth by tree-ring analysis is used to assess the effect of acid precipitation. The pattern and historical trends of acid precipitation deposition are compared with growth trends from mature forest stands in New Hampshire and Tennessee. No clear indication of a regional, synchronized decrease in tree growth was found. The...

Homoserine as an Aspartic Acid Precursor for Synthesis of Proteoglycan Glycopeptide Containing Aspartic Acid and Sulfated Glycan Chain

OpenAIRE

Yang, Weizhun; Ramadan, Sherif; Yang, Bo; Yoshida, Keisuke; Huang, Xuefei

2016-01-01

Among many hurdles in synthesizing proteoglycan glycopeptides, one challenge is the incorporation of aspartic acid in the peptide backbone and acid sensitive O-sulfated glycan chains. To overcome this, a new strategy was developed utilizing homoserine as an aspartic acid precursor. The conversion of homoserine to aspartic acid in the glycopeptide was successfully accomplished by late stage oxidation using 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) and bis(acetoxy)iodobenzene (BAIB). This is...

Wet milling versus co-precipitation in magnetite ferrofluid preparation

Directory of Open Access Journals (Sweden)

Almásy László

2015-01-01

Full Text Available Various uses of ferrofluids for technical applications continuously raise the interest in improvement and optimization of preparation methods. This paper deals with preparation of finely granulated magnetite particles coated with oleic acid in hydrocarbon suspensions following either chemical co-precipitation from iron salt precursors or wet milling of micron size magnetite powder with the goal to compare the benefits and disadvantages of each method. Microstructural measurements showed that both methods gave similar magnetite particle size of 10-15 nm. Higher saturation magnetization was achieved for the wet-milled magnetite suspension compared to relatively rapid co-precipitation synthesis. Different efficacies of ferrophase incorporation into kerosene could be related to the different mechanisms of oleic acid bonding to nanoparticle surface. The comparative data show that wet milling represents a practicable alternative to the traditional co-precipitation since despite of longer processing time, chemicals impact on environment can be avoided as well as the remnant water in the final product.

The influence of different matrices on the nature and content of haloacetic acids precursors in ozonized water

Directory of Open Access Journals (Sweden)

Molnar Jelena J.

2012-01-01

Full Text Available This paper investigates the influence of different matrices (groundwater a realistic natural matrix and commercial humic acid solution a synthetic matrix on the nature and content of haloacetic acid (HAA precursors in ozonized water (0.4 to 3.0 mg O3/mg DOC; pH 6. Natural organic matter (NOM characterization of the natural matrix showed it was largely of hydrophobic character (65% fulvic and 14% humic acids, with the hydrophilic fractions HPIA and HPI-NA at 12% and 9%, respectively. At approximately the same dissolved organic carbon (DOC content of the investigated matrices (~10 mg /L, a greater degree of hydrophobicity was seen in the humic acid solution than in the natural matrix, resulting in a higher content of HAA precursors (559 ± 21 μg/L in the synthetic matrix compared to 309 ± 15 μg/L in the natural matrix. By applying different ozone doses (0.4 to 3.0 mg O3/mg DOC, the DOC content of the studied matrices was reduced by 6-22%, with a maximum process efficacy being achieved with 3.0 mg O3/mg DOC. Ozonation also lead to changes in the NOM structure, i.e. complete oxidation of the humic acid fractions in both investigated matrices. After oxidation, hydrophilic structures dominate the natural water matrix (65%, whereas the synthetic matrix has an equal distribution of hydrophobic and hydrophilic fractions (~50%. Changes in the content and structure of NOM during ozonation resulted in the reduction of the total HAA precursors content (63-85%, using 3.0 mg O3/mg DOC. Detailed analysis of the reactivity of the residual HAA precursor materials shows that ozonation using 3.0 mg O3/mg DOC reduced the reactivity of the NOM fractions in comparison to the raw water. By contrast, HAA precursor material present in the commercial HA solution was transformed after ozonation into other reactive compounds, i.e. precursors which originated from the fulvic acid and hydrophilic fractions. The results of the laboratory testing indicate that the

Co-precipitation synthesis and luminescence behavior of Ce-doped yttrium aluminum garnet (YAG:Ce) phosphor: The effect of precipitant

International Nuclear Information System (INIS)

Zhang Kai; Liu Hezhou; Wu Yating; Hu Wenbin

2008-01-01

YAG:Ce precursors were co-precipitated using ammonia water and ammonium hydrogen carbonate as precipitants, respectively. Phase transition of the precursors during sintering was compared between the two precipitants. The precursors synthesized with ammonia water transformed to YAG at about 1000 deg. C via YAlO 3 phase. The precursors synthesized with ammonium hydrogen carbonate directly converted to pure YAG at about 900 deg. C. Comparing the powders produced with the two precipitants, the powders produced with ammonia hydrogen carbonate showed good dispersity. When sintered at 1600 deg. C, aggregation of the powders synthesized with the two precipitants both became severe. With increase the sintering temperature, the maximum wavelength of excitation and emission spectra of the phosphors synthesized with ammonium water hardly varied. While the maximum wavelength of excitation spectra of the phosphors synthesized with ammonium hydrogen carbonate unchanged, and the emission spectra showed red shift. Because of size effect and higher loss of cerium content, the emission intensity of phosphors prepared with ammonium hydrogen carbonate was lower than the phosphors prepared with ammonium water, when sintered at the same temperature

Acid precipitation literature review

Energy Technology Data Exchange (ETDEWEB)

Seip, H M; Andersen, B; Andersson, G; Hov, Oe; Kucera, V; Moseholm, L

1986-01-01

There is an increasing number of publications on acid deposition and related phenomena. Interest in these topics has also been reflected in a considerable number of meetings and conferences in this field. The largest of these in 1985 was the ''International Symposium on Acidic Precipitation'' (Muskoka, Ontario). Most work so far has been carried out in North America and Europe. There is, however, an increasing interest in obtaining a better picture of sensitive areas and possible acidification in other parts of the world. Anthropogenic SO/sub 2/ emissions have been estimated to be (in TgSyr/sup -1/): 2.4 (Africa), 4.1 (South America), 0.7 (Ocenia), and 18.3 (Asia). The largest increase during the last decade has been in Asia. Based on Studies of precipitation in remote areas it has been suggested that the natural background concentration for sulphate in many areas should be about 6 ..mu..eq 1/sup -1/. A new study of sulphate and nitrate in Greenland snow showed that both ions increased by a factor of about 2 from 1895 to 1978. The concentrations of SO/sub 2/ at Norwegian rural sites show a decreasing trend since late 1970s, while concentrations of sulphate in air show no clear trend. More reliable models for transformation, transport and deposition of chemicals are being developed, including three-dimensional grid models to describe episodes of elevated pollution levels lasting for a few days. Model calculations indicate that control of hydrocarbon (HC) emissions is much more efficient in reducing the ozone level in southern Scandinavia in episodes influenced by long-range transported pollutants than NO/sub x/ control of combined NO/sub x/ and HC control. 36 refs. (EG).

Condensation of the isoprenoid and amino precursors in the biosynthesis of domoic acid.

Science.gov (United States)

Savage, Thomas J; Smith, G Jason; Clark, Amy T; Saucedo, Portia N

2012-01-01

Understanding how environmental signals regulate production of domoic acid in blooms of Pseudo-nitzschia spp. at a molecular level requires description of the biochemical pathway to this kainoid neurotoxin. Precursor feeding studies have suggested domoic acid arises from the condensation of the C(10) isoprenoid geranyl diphosphate with glutamate, but the specific reactions leading to domoic acid from these precursors remain undescribed. Here, we develop a method to derivatize domoic acid with propyl chloroformate that enables gas chromatography-mass spectrometry (GC-MS) analysis to measure incorporation of stable isotopes into domoic acid generated in cultures incubated with isotopically-labeled substrates. We apply this method to demonstrate that both (2)H from [1-(2)H(2)]geraniol are incorporated into domoic acid, suggesting that the condensation of geranyl diphosphate with an amino group occurs by nucleophilic substitution of the diphosphate rather than by oxidation of geraniol to the aldehyde before reaction with an amino group to form an imine. Ultimately, these and similar studies will facilitate the identification of DA biosynthetic enzymes and genes which will enable the study of how environmental factors regulate DA biosynthesis at the molecular level. Copyright © 2011 Elsevier Ltd. All rights reserved.

The Role of Poly(Aspartic Acid) in the Precipitation of Calcium Phosphate in Confinement.

Science.gov (United States)

Cantaert, Bram; Beniash, Elia; Meldrum, Fiona C

2013-12-28

Many questions remain regarding the formation of ultrathin hydroxapatite (HAP) crystals within the confines of collagen fibrils of bones. These structures form through the interplay of the collagen matrix and non-collagenous proteins, and in vitro mineralization studies employing poly(aspartic acid) (PAsp) as a mimic of the non-collagenous proteins have generated mineralized fibrils with structures comparable to their biogenic counterparts. In this article, we employ the nanoscale cylindrical pores perforating track-etch filtration membranes to investigate the role of PAsp in controlling the infiltration and crystallization of calcium phosphate (CaP) within confined volumes. Oriented polycrystalline HAP and non-oriented octacalcium phosphate (OCP) rods precipitated within the membrane pores via an amorphous calcium phosphate (ACP) precursor, where PAsp increased the proportion of OCP rods. Further, ACP crystallized faster within the membranes than in bulk solution when PAsp was present, suggesting that PAsp inhibits crystallization in solution, but promotes it when bound to a substrate. Finally, in contrast to the collagen system, PAsp reduced the yield of intra-membrane mineral and failed to enhance infiltration. This suggests that a specific interaction between the collagen matrix and ACP/PAsp precursor particles drives effective infiltration. Thus, while orientation of HAP crystals can be achieved by confinement alone, the chemistry of the collagen matrix is necessary for efficient mineralisation with CaP.

Long range transport of air pollutants in Europe and acid precipitation in Norway

Science.gov (United States)

Jack Nordo

1976-01-01

Observations show that pollutants from large emission sources may cause significant air concentrations 500 to 1000 miles away. Very acid precipitation occurs in such periods. The scavenging is often intensified by the topography. Case studies will be presented, with special emphasis on acid precipitation in Scandinavia. Large scale dispersion models have been developed...

Study of molybdenum (VI) complexation and precipitation by zirconium (IV) in strongly acid medium. Application to nuclear spent fuel dissolution; Etude de la complexation et de la precipitation du molybdene (VI) par le zirconium (IV) en milieu tres acide. Application a la dissolution du combustible nucleaire irradie

Energy Technology Data Exchange (ETDEWEB)

Esbelin, E

1999-07-01

These last years the formation of solid deposits has been observed in the dissolution workshops of the La Hague plant. A sample of the solid was withdrawn for expertise: molybdenum and zirconium are the two major components of the solid, identified as zirconium molybdate. This thesis consisted in the approach of the mechanisms in solution liable to induce precipitate formation. After a bibliographical overview on the chemistry of Mo(VI) in highly acidic solution, this system was studied by absorption spectrophotometry in perchloric medium. The implication of two major forms of Mo(VI) in a dimerization equilibrium was confirmed by this way and by {sup 95}Mo NMR. The principal parameters governing this equilibrium were identified. It is thus shown that the molybdenum dimerization reaction is exothermic. Disturbance of the Mo(VI) system in highly acidic solution by Zr(IV) was also studied. In a restricted experimental field, for which 'conventional' exploitation methodologies had to be adapted to the system, a main complex of stoichiometry 1:1 between Mo(VI) and Zr(IV) was found. The precipitation study of Mo(VI) by Zr(IV) under conditions close to those of the dissolution medium of nuclear spent fuel was undertaken. The main parameters which control precipitation kinetics were identified. The results obtained reveal that precipitation is controlled by a single macroscopic process and therefore can be described by a single equation. The solid obtained is composed of only one phase presenting a Mo:Zr non-stoichiometry when compared to the theoretical formula ZrMo{sub 2}O{sub 7}(OH){sub 2},2H{sub 2}O. At last, on the basis of the research results, a descriptive mechanism of the system is proposed in which intervenes a 1:1 intermediate complex, much more soluble than a probable 2:1 precipitation precursor. (author)

Acidic precipitation. Volume 4: Soils, aquatic processes, and lake acidification. Advances in environmental science

Energy Technology Data Exchange (ETDEWEB)

Norton, S.A.; Lindberg, S.E.; Page, A.L. (eds.)

1990-01-01

Acidic precipitation and its effects have been the focus of intense research for over two decades. Recently, research has focused on a greater understanding of dose-response relationships between atmospheric loading of acidifying material and lake acidity. This volume of the subseries Acidic Precipitation emphasizes acid neutralizing processes and the capacity of terrestrial and aquatic systems to assimilate acidifying substances and, conversely, the ability of systems to recover after acid loading diminishes. Eight chapters have been processed separately for inclusion in the appropriate data bases.

Amphibian recovery after a decrease in acidic precipitation.

Science.gov (United States)

Dolmen, Dag; Finstad, Anders Gravbrøt; Skei, Jon Kristian

2018-04-01

We here report the first sign of amphibian recovery after a strong decline due to acidic precipitation over many decades and peaking around 1980-90. In 2010, the pH level of ponds and small lakes in two heavily acidified areas in southwestern Scandinavia (Aust-Agder and Østfold in Norway) had risen significantly at an (arithmetic) average of 0.14 since 1988-89. Parallel with the general rise in pH, amphibians (Rana temporaria, R. arvalis, Bufo bufo, Lissotriton vulgaris, and Triturus cristatus) had become significantly more common: the frequency of amphibian localities rose from 33% to 49% (n = 115), and the average number of amphibian species per locality had risen from 0.51 to 0.88. In two other (reference) areas, one with better buffering capacity (Telemark, n = 21) and the other with much less input of acidic precipitation (Nord-Trøndelag, n = 106), there were no significant changes in pH or amphibians.

Homoserine as an Aspartic Acid Precursor for Synthesis of Proteoglycan Glycopeptide Containing Aspartic Acid and a Sulfated Glycan Chain.

Science.gov (United States)

Yang, Weizhun; Ramadan, Sherif; Yang, Bo; Yoshida, Keisuke; Huang, Xuefei

2016-12-02

Among many hurdles in synthesizing proteoglycan glycopeptides, one challenge is the incorporation of aspartic acid in the peptide backbone and acid sensitive O-sulfated glycan chains. To overcome this, a new strategy was developed utilizing homoserine as an aspartic acid precursor. The conversion of homoserine to aspartic acid in the glycopeptide was successfully accomplished by late stage oxidation using (2,2,6,6-tetramethyl-piperidin-1-yl)oxyl (TEMPO) and bis(acetoxy)iodobenzene (BAIB). This is the first time that a glycopeptide containing aspartic acid and an O-sulfated glycan was synthesized.

Ten-year study on acid precipitation nears conclusion

International Nuclear Information System (INIS)

Olem, H.

1990-01-01

Results from the National Acid Precipitation Assessment Program (NAPAP) are discussed. Final results are contained in 26 state of the science reports. Seven of the reports provide information on acid rain and aquatic ecosystems. They describe the current state of acidic surface waters, watershed processes affecting surface water chemistry, historical evidence for surface water acidification, methods for forecasting future changes, and the response of acidic surface water to liming. Six areas of the country were found to be of special interest: southwest Adirondacks, New England, forested areas of the mid-Atlantic highlands, the Atlantic coastal plain, the northern Florida highlands, parts of northeastern Wisconsin and the Upper Peninsula of Michigan. Environmental effects, mitigation efforts and possible legislation are briefly discussed

Generation, Release, and Uptake of the NAD Precursor Nicotinic Acid Riboside by Human Cells.

Science.gov (United States)

Kulikova, Veronika; Shabalin, Konstantin; Nerinovski, Kirill; Dölle, Christian; Niere, Marc; Yakimov, Alexander; Redpath, Philip; Khodorkovskiy, Mikhail; Migaud, Marie E; Ziegler, Mathias; Nikiforov, Andrey

2015-11-06

NAD is essential for cellular metabolism and has a key role in various signaling pathways in human cells. To ensure proper control of vital reactions, NAD must be permanently resynthesized. Nicotinamide and nicotinic acid as well as nicotinamide riboside (NR) and nicotinic acid riboside (NAR) are the major precursors for NAD biosynthesis in humans. In this study, we explored whether the ribosides NR and NAR can be generated in human cells. We demonstrate that purified, recombinant human cytosolic 5'-nucleotidases (5'-NTs) CN-II and CN-III, but not CN-IA, can dephosphorylate the mononucleotides nicotinamide mononucleotide and nicotinic acid mononucleotide (NAMN) and thus catalyze NR and NAR formation in vitro. Similar to their counterpart from yeast, Sdt1, the human 5'-NTs require high (millimolar) concentrations of nicotinamide mononucleotide or NAMN for efficient catalysis. Overexpression of FLAG-tagged CN-II and CN-III in HEK293 and HepG2 cells resulted in the formation and release of NAR. However, NAR accumulation in the culture medium of these cells was only detectable under conditions that led to increased NAMN production from nicotinic acid. The amount of NAR released from cells engineered for increased NAMN production was sufficient to maintain viability of surrounding cells unable to use any other NAD precursor. Moreover, we found that untransfected HeLa cells produce and release sufficient amounts of NAR and NR under normal culture conditions. Collectively, our results indicate that cytosolic 5'-NTs participate in the conversion of NAD precursors and establish NR and NAR as integral constituents of human NAD metabolism. In addition, they point to the possibility that different cell types might facilitate each other's NAD supply by providing alternative precursors. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

Lichenysin production is improved in codY null Bacillus licheniformis by addition of precursor amino acids.

Science.gov (United States)

Zhu, Chengjun; Xiao, Fang; Qiu, Yimin; Wang, Qin; He, Zhili; Chen, Shouwen

2017-08-01

Lichenysin is categorized into the family of lipopeptide biosurfactants and has a variety of applications in the petroleum industry, bioremediation, pharmaceuticals, and the food industry. Currently, large-scale production is limited due to the low yield. This study found that lichenysin production was repressed by supplementation of extracellular amino acids. The global transcriptional factor CodY was hypothesized to prevent lichenysin biosynthesis under an amino acid-rich condition in Bacillus licheniformis. Thus, the codY null strain was constructed, and lichenysin production was increased by 31.0% to 2356 mg/L with the addition of precursor amino acids, and the lichenysin production efficiency was improved by 42.8% to 98.2 mg/L• h. Correspondingly, the transcription levels of the lichenysin synthetase gene lchAA, and its corresponding regulator genes comA, degQ, and degU, were upregulated. Also, the codY deletion enhanced biosynthesis of lichenysin precursor amino acids (Gln, Ile, Leu, and Val) and reduced the formation of byproducts, acetate, acetoin, and 2,3-butanediol. This study firstly reported that lichenysin biosynthesis was negatively regulated by CodY and lichenysin production could be further improved with the precursor amino acid amendment in the codY null strain.

Glycation inhibits trichloroacetic acid (TCA)-induced whey protein precipitation

Science.gov (United States)

Four different WPI saccharide conjugates were successfully prepared to test whether glycation could inhibit WPI precipitation induced by trichloroacetic acid (TCA). Conjugates molecular weights after glycation were analyzed with SDS-PAGE. No significant secondary structure change due to glycation wa...

Application of a precipitation method for uranium recovery from abu-zaabal phosphoric acid plant, Egypt

International Nuclear Information System (INIS)

El-hazek, N.M.T.; Hussein, E.M.

1995-01-01

Current industrial recovery of uranium from 30% phosphoric acid-produced by the dihydrate process-is based on solvent extraction method. Uranium recovery from concentrated phosphoric acid (45-52% p o5 ) produced by evaporation of the 30% acid or directly produced by the hemihydrate process, by solvent extraction is difficult to apply in practice. In addition to possible contamination of the acid by the organic solvents and/or their deterioration. This paper investigates the possibility of applying a precipitation method (Weterings and Janssen, 1985) for uranium recovery from both low (28% P 2 O 5 ) and high (48% P 2 O 5 ) concentration phosphoric acids produced by abu-zaabal phosphoric acid plant (Abuzaabal fertilizers and chemicals Co., Egypt). The 28% acid produced by H 2 SO 4 dihydrate method and the 48% acid produced by evaporation of the 28% acid The applied precipitation method depends on using NH 4 F as a uranium precipitant from both low and high concentration phosphoric acids in presence of acetone as a dispersing agent. All the relevant factors have been studied

One-pot synthesis of amino acid precursors with insoluble organic matter in planetesimals with aqueous activity

Science.gov (United States)

Kebukawa, Yoko; Chan, Queenie H. S.; Tachibana, Shogo; Kobayashi, Kensei; Zolensky, Michael E.

2017-01-01

The exogenous delivery of organic molecules could have played an important role in the emergence of life on the early Earth. Carbonaceous chondrites are known to contain indigenous amino acids as well as various organic compounds and complex macromolecular materials, such as the so-called insoluble organic matter (IOM), but the origins of the organic matter are still subject to debate. We report that the water-soluble amino acid precursors are synthesized from formaldehyde, glycolaldehyde, and ammonia with the presence of liquid water, simultaneously with macromolecular organic solids similar to the chondritic IOM. Amino acid products from hydrothermal experiments after acid hydrolysis include α-, β-, and γ-amino acids up to five carbons, for which relative abundances are similar to those extracted from carbonaceous chondrites. One-pot aqueous processing from simple ubiquitous molecules can thus produce a wide variety of meteoritic organic matter from amino acid precursors to macromolecular IOM in chondrite parent bodies. PMID:28345041

Precipitation of plutonium from acidic solutions using magnesium oxide

International Nuclear Information System (INIS)

Jones, S.A.

1994-01-01

Plutonium (IV) is only marginally soluble in alkaline solution. Precipitation of plutonium using sodium or potassium hydroxide to neutralize acidic solutions produces a gelatinous solid that is difficult to filter and an endpoint that is difficult to control. If the pH of the solution is too high, additional species precipitate producing an increased volume of solids separated. The use of magnesium oxide as a reagent has advantages. It is added as a solid (volume of liquid waste produced is minimized), the pH is self-limiting (pH does not exceed about 8.5), and the solids precipitated are more granular (larger particle size) than those produced using KOH or NaOH. Following precipitation, the raffinate is expected to meet criteria for disposal to tank farms. The solid will be heated in a furnace to dry it and convert any hydroxide salts to the oxide form. The material will be cooled in a desiccator. The material is expected to meet vault storage criteria

Probing Coagulation Behavior of Individual Aluminum Species for Removing Corresponding Disinfection Byproduct Precursors: The Role of Specific Ultraviolet Absorbance.

Directory of Open Access Journals (Sweden)

He Zhao

Full Text Available Coagulation behavior of aluminum chloride and polyaluminum chloride (PACl for removing corresponding disinfection byproduct (DBP precursors was discussed in this paper. CHCl3, bromine trihalomethanes (THM-Br, dichloroacetic acid (DCAA and trichloroacetic acid (TCAA formation potential yields were correlated with specific ultraviolet absorbance (SUVA values in different molecular weight (MW fractions of humic substances (HS, respectively. Correlation analyses and principal component analysis were performed to examine the relationships between SUVA and different DBP precursors. To acquire more structural characters of DBP precursors and aluminum speciation, freeze-dried precipitates were analyzed by fourier transform infrared (FTIR and C 1s, Al 2p X-ray photoelectron spectroscopy (XPS. The results indicated that TCAA precursors (no MW limits, DCAA and CHCl3 precursors in low MW fractions (MW30 kDa were preferentially removed by PACl coagulation with preformed Al13 species at pH 5.0. Additionally, for DCAA precursors in high MW fractions (MW>30 kDa with relatively low aromatic content and more carboxylic structures, the greatest removal occurred at pH 6.0 through PACl coagulation with aggregated Al13 species.

Aerosol and precipitation chemistry in the southwestern United States: spatiotemporal trends and interrelationships

Science.gov (United States)

Sorooshian, A.; Shingler, T.; Harpold, A.; Feagles, C. W.; Meixner, T.; Brooks, P. D.

2013-08-01

This study characterizes the spatial and temporal patterns of aerosol and precipitation composition at six sites across the United States Southwest between 1995 and 2010. Precipitation accumulation occurs mostly during the wintertime (December-February) and during the monsoon season (July-September). Rain and snow pH levels are usually between 5-6, with crustal-derived species playing a major role in acid neutralization. These species (Ca2+, Mg2+, K+, Na+) exhibit their highest concentrations between March and June in both PM2.5 and precipitation due mostly to dust. Crustal-derived species concentrations in precipitation exhibit positive relationships with SO42-, NO3-, and Cl-, suggesting that acidic gases likely react with and partition to either crustal particles or hydrometeors enriched with crustal constituents. Concentrations of particulate SO42- show a statistically significant correlation with rain SO42- unlike snow SO42-, which may be related to some combination of the vertical distribution of SO42- (and precursors) and the varying degree to which SO42--enriched particles act as cloud condensation nuclei versus ice nuclei in the region. The coarse : fine aerosol mass ratio was correlated with crustal species concentrations in snow unlike rain, suggestive of a preferential role of coarse particles (mainly dust) as ice nuclei in the region. Precipitation NO3- : SO42- ratios exhibit the following features with potential explanations discussed: (i) they are higher in precipitation as compared to PM2.5; (ii) they exhibit the opposite annual cycle compared to particulate NO3- : SO42- ratios; and (iii) they are higher in snow relative to rain during the wintertime. Long-term trend analysis for the monsoon season shows that the NO3- : SO42- ratio in rain increased at the majority of sites due mostly to air pollution regulations of SO42- precursors.

Synthesis of InGaZnO4 nanoparticles using low temperature multistep co-precipitation method

International Nuclear Information System (INIS)

Wu, Ming-Chung; Hsiao, Kai-Chi; Lu, Hsin-Chun

2015-01-01

Indium gallium zinc oxide (InGaZnO 4 , IGZO) has attracted explosive growth in investigations over the last decades as an important material in the thin-film transistor. In this study, the various nitrate precursors, including indium nitrate, gallium nitrate, and zinc nitrate, were prepared from the various metals dissolved in nitric acid. Then, we used these nitrate precursors to synthesize the IGZO precursor powder by the multistep co-precipitation method. The synthesis parameters of the co-precipitation method, such as reaction temperature, pH value and reaction time, were controlled precisely to prepare the high quality IGZO precursor powder. Finally, IGZO precursor powder was calcined at 900 °C. Then, the microstructure, the crystalline structure, the particle size distribution and specific surface area of calcined IGZO precursor powder were characterized by electron transmission microscopy, X-ray diffraction technique, dynamic light scattering method and the surface area and porosimetry analyzer, respectively. The relative density of IGZO tablet sintered at 1200 °C for 12 h is as high as 97.30%, and it showed highly InGaZnO 4 crystalline structure and the large grain size. The IGZO nanoparticles developed in our study has the potential for the high quality target materials used in the application of electronic devices. - Graphical abstract: Display Omitted - Highlights: • InGaZnO 4 (IGZO) nanoparticle was synthesized by multistep co-precipitation method. • The synthesis parameters were controlled precisely to prepare high quality powder. • The relative density of highly crystalline IGZO tablet is as high as 97.30%. • IGZO tablet exhibited highly crystalline structure and the large grain size

Precursor Amino Acids Inhibit Polymyxin E Biosynthesis in Paenibacillus polymyxa, Probably by Affecting the Expression of Polymyxin E Biosynthesis-Associated Genes

Directory of Open Access Journals (Sweden)

Zhiliang Yu

2015-01-01

Full Text Available Polymyxin E belongs to cationic polypeptide antibiotic bearing four types of direct precursor amino acids including L-2,4-diaminobutyric acid (L-Dab, L-Leu, D-Leu, and L-Thr. The objective of this study is to evaluate the effect of addition of precursor amino acids during fermentation on polymyxin E biosynthesis in Paenibacillus polymyxa. The results showed that, after 35 h fermentation, addition of direct precursor amino acids to certain concentration significantly inhibited polymyxin E production and affected the expression of genes involved in its biosynthesis. L-Dab repressed the expression of polymyxin synthetase genes pmxA and pmxE, as well as 2,4-diaminobutyrate aminotransferase gene ectB; both L-Leu and D-Leu repressed the pmxA expression. In addition, L-Thr affected the expression of not only pmxA, but also regulatory genes spo0A and abrB. As L-Dab precursor, L-Asp repressed the expression of ectB, pmxA, and pmxE. Moreover, it affected the expression of spo0A and abrB. In contrast, L-Phe, a nonprecursor amino acid, had no obvious effect on polymyxin E biosynthesis and those biosynthesis-related genes expression. Taken together, our data demonstrated that addition of precursor amino acids during fermentation will inhibit polymyxin E production probably by affecting the expression of its biosynthesis-related genes.

Transcriptome analysis of bitter acid biosynthesis and precursor pathways in hop (Humulus lupulus

Directory of Open Access Journals (Sweden)

Clark Shawn M

2013-01-01

Full Text Available Abstract Background Bitter acids (e.g. humulone are prenylated polyketides synthesized in lupulin glands of the hop plant (Humulus lupulus which are important contributors to the bitter flavour and stability of beer. Bitter acids are formed from acyl-CoA precursors derived from branched-chain amino acid (BCAA degradation and C5 prenyl diphosphates from the methyl-D-erythritol 4-phosphate (MEP pathway. We used RNA sequencing (RNA-seq to obtain the transcriptomes of isolated lupulin glands, cones with glands removed and leaves from high α-acid hop cultivars, and analyzed these datasets for genes involved in bitter acid biosynthesis including the supply of major precursors. We also measured the levels of BCAAs, acyl-CoA intermediates, and bitter acids in glands, cones and leaves. Results Transcripts encoding all the enzymes of BCAA metabolism were significantly more abundant in lupulin glands, indicating that BCAA biosynthesis and subsequent degradation occurs in these specialized cells. Branched-chain acyl-CoAs and bitter acids were present at higher levels in glands compared with leaves and cones. RNA-seq analysis showed the gland-specific expression of the MEP pathway, enzymes of sucrose degradation and several transcription factors that may regulate bitter acid biosynthesis in glands. Two branched-chain aminotransferase (BCAT enzymes, HlBCAT1 and HlBCAT2, were abundant, with gene expression quantification by RNA-seq and qRT-PCR indicating that HlBCAT1 was specific to glands while HlBCAT2 was present in glands, cones and leaves. Recombinant HlBCAT1 and HlBCAT2 catalyzed forward (biosynthetic and reverse (catabolic reactions with similar kinetic parameters. HlBCAT1 is targeted to mitochondria where it likely plays a role in BCAA catabolism. HlBCAT2 is a plastidial enzyme likely involved in BCAA biosynthesis. Phylogenetic analysis of the hop BCATs and those from other plants showed that they group into distinct biosynthetic (plastidial and

Synthesis of Amino Acid Precursors with Organic Solids in Planetesimals with Liquid Water

Science.gov (United States)

Kebukawa, Y; Misawa, S.; Matsukuma, J.; Chan, Q. H. S.; Kobayashi, J.; Tachibana, S.; Zolensky, M. E.

2017-01-01

Amino acids are important ingredients of life that would have been delivered to Earth by extraterrestrial sources, e.g., comets and meteorites. Amino acids are found in aqueously altered carbonaceous chondrites in good part in the form of precursors that release amino acids after acid hydrolysis. Meanwhile, most of the organic carbon (greater than 70 weight %) in carbonaceous chondrites exists in the form of solvent insoluble organic matter (IOM) with complex macromolecular structures. Complex macromolecular organic matter can be produced by either photolysis of interstellar ices or aqueous chemistry in planetesimals. We focused on the synthesis of amino acids during aqueous alteration, and demonstrated one-pot synthesis of a complex suite of amino acids simultaneously with IOM via hydrothermal experiments simulating the aqueous processing

One-step routes from di- and triblock copolymer precursors to hydrophilic nanoporous poly(acrylic acid)-b-polystyrene

DEFF Research Database (Denmark)

Guo, Fengxiao; Jankova Atanasova, Katja; Schulte, Lars

2008-01-01

Nanoporous polystyrene with hydrophilic pores was prepared from di- and triblock copolymer precursors. The precursor material was either a poly(tert-butyl acryl ate)-b-polystyrene (PtBA-b-PS) diblock copolymer synthesized by atom transfer radical polymerization (ATRP) or a polydimethylsiloxane......-b-poly(tertbutyl acrylate)-b-polystyrene (PDMS-b-PtBA-b-PS) triblock copolymer synthesized by a combination of living anionic polymerization and ATRP. In the latter copolymer, PS was the matrix and mechanically stable component, PtBA was converted by acidic deprotection to hydrophilic poly(acrylic acid) (PAA) providing...

Synthesis of InGaZnO{sub 4} nanoparticles using low temperature multistep co-precipitation method

Energy Technology Data Exchange (ETDEWEB)

Wu, Ming-Chung, E-mail: mingchungwu@mail.cgu.edu.tw; Hsiao, Kai-Chi; Lu, Hsin-Chun

2015-07-15

Indium gallium zinc oxide (InGaZnO{sub 4}, IGZO) has attracted explosive growth in investigations over the last decades as an important material in the thin-film transistor. In this study, the various nitrate precursors, including indium nitrate, gallium nitrate, and zinc nitrate, were prepared from the various metals dissolved in nitric acid. Then, we used these nitrate precursors to synthesize the IGZO precursor powder by the multistep co-precipitation method. The synthesis parameters of the co-precipitation method, such as reaction temperature, pH value and reaction time, were controlled precisely to prepare the high quality IGZO precursor powder. Finally, IGZO precursor powder was calcined at 900 °C. Then, the microstructure, the crystalline structure, the particle size distribution and specific surface area of calcined IGZO precursor powder were characterized by electron transmission microscopy, X-ray diffraction technique, dynamic light scattering method and the surface area and porosimetry analyzer, respectively. The relative density of IGZO tablet sintered at 1200 °C for 12 h is as high as 97.30%, and it showed highly InGaZnO{sub 4} crystalline structure and the large grain size. The IGZO nanoparticles developed in our study has the potential for the high quality target materials used in the application of electronic devices. - Graphical abstract: Display Omitted - Highlights: • InGaZnO{sub 4} (IGZO) nanoparticle was synthesized by multistep co-precipitation method. • The synthesis parameters were controlled precisely to prepare high quality powder. • The relative density of highly crystalline IGZO tablet is as high as 97.30%. • IGZO tablet exhibited highly crystalline structure and the large grain size.

Effects of a combination of elicitation and precursor feeding on grape amino acid composition through foliar applications to Garnacha vineyard.

Science.gov (United States)

Gutiérrez-Gamboa, Gastón; Portu, Javier; López, Rosa; Santamaría, Pilar; Garde-Cerdán, Teresa

2018-04-01

Vine foliar applications of phenylalanine (Phe) or methyl jasmonate (MeJ) could improve the synthesis of secondary metabolites. However, there are no reports focusing on the effects of elicitation supported by precursor feeding on must amino acid composition in grapevines. The aim of this research was to study the effect of the elicitation of methyl jasmonate (MeJ) supported by phenylalanine (Phe) as a precursor feeding (MeJ+Phe) and its application individually on must amino acid composition. Results showed that foliar Phe and MeJ treatments decreased the concentration of most of the studied amino acids with respect to the control (p≤0.05). MeJ+Phe treatment did not affect must nitrogen content. Musts obtained from MeJ+Phe showed higher concentration of several amino acids than samples from Phe and MeJ applications. Therefore, other sources of precursor feeding could support elicitation, to improve amino acid composition and be considered as a tool for viticulture. Copyright © 2017 Elsevier Ltd. All rights reserved.

Third generation capture system: precipitating amino acid solvent systems

NARCIS (Netherlands)

Sanchez Fernandez, E.; Misiak, K.; Ham, L. van der; Goetheer, E.L.V.

2013-01-01

This work summarises the results of the design of novel separation processes for CO2 removal from flue gas based on precipitating amino acid solvents. The processes here described (DECAB, DECAB Plus and pH-swing) use a combination of enhanced CO2 absorption (based on the Le Chatelier’s principle)

Effect of amino acids on the precipitation kinetics and Ca isotopic composition of gypsum

Science.gov (United States)

Harouaka, Khadouja; Kubicki, James D.; Fantle, Matthew S.

2017-12-01

Stirred gypsum (CaSO4 · 2H2O) precipitation experiments (initial Ωgypsum = 2.4 ± 0.14, duration ≈ 1.0-1.5 h) were conducted in the presence of the amino acids glycine (190 μM), L-alanine (190 μM), D- and L-arginine (45 μM), and L-tyrosine (200 μM) to investigate the effect of simple organic compounds on both the precipitation kinetics and Ca isotopic composition of gypsum. Relative to abiotic controls, glycine, tyrosine, and alanine inhibited precipitation rates by ∼22%, 27%, and 29%, respectively, while L- and D-arginine accelerated crystal growth by ∼8% and 48%, respectively. With the exception of tyrosine, amino acid induced inhibition resulted in fractionation factors (αs-f) associated with precipitation that were no more than 0.3‰ lower than amino acid-free controls. In contrast, the tyrosine and D- and L-arginine experiments had αs-f values associated with precipitation that were similar to the controls. Our experimental results indicate that Ca isotopic fractionation associated with gypsum precipitation is impacted by growth inhibition in the presence of amino acids. Specifically, we propose that the surface-specific binding of amino acids to gypsum can change the equilibrium fractionation factor of the bulk mineral. We investigate the hypothesis that amino acids can influence the growth of gypsum at specific crystal faces via adsorption and that different faces have distinct fractionation factors (αface-fluid). Accordingly, preferential sorption of amino acids at particular faces changes the relative, face-specific mass fluxes of Ca during growth, which influences the bulk isotopic composition of the mineral. Density functional theory (DFT) calculations suggest that the energetic favorability of glycine sorption onto gypsum crystal faces occurs in the order: (1 1 0) > (0 1 0) > (1 2 0) > (0 1 1), while glycine sorption onto the (-1 1 1) face was found to be energetically unfavorable. Face-specific fractionation factors constrained by

Studies on Pu(IV)/(III)-oxalate precipitation from nitric acid containing high concentration of calcium and fluoride ions

International Nuclear Information System (INIS)

Kalsi, P.K.; Pawar, S.M.; Ghadse, D.R.; Joshi, A.R.; Ramakrishna, V.V.; Vaidya, V.N.; Venugopal, V.

2003-01-01

Plutonium (IV)/(III) oxalate precipitation from nitric acid solution, containing large amount of calcium and fluoride ions was investigated. It was observed that direct precipitation of Pu (IV) oxalate from nitric acid containing large amount of calcium and fluoride ions did not give good decontamination of Pu from calcium and fluoride impurities. However, incorporation of hydroxide precipitation using ammonium hydroxide prior to Pu (IV) oxalate precipitation results into PuO 2 with much less calcium and fluoride impurities. Whereas, good decontamination from calcium and fluoride impurities could be obtained by employing Pu (III) oxalate precipitation directly from nitric acid containing large amount of calcium and fluoride ions. A method was also developed to recover Pu from the oxalate waste containing calcium and fluoride ions. (author)

Optimization of precipitation conditions of thorium oxalate precipitate

International Nuclear Information System (INIS)

Pazukhin, Eh.M.; Smirnova, E.A.; Krivokhatskij, A.S.; Pazukhina, Yu.L.; Kiselev, P.P.

1986-01-01

Thorium precipitation in the form of difficultly soluble oxalate has been investigated. The equation binding the concentration of metal with the nitric acid in the initial solution and quantity of a precipitator necessary for minimization of desired product losses is derived. The graphical solution of this equation for a case, when the oxalic acid with 0.78 mol/l concentration is the precipitator, is presented

Precipitation of plutonium from acidic solutions using magnesium oxide

International Nuclear Information System (INIS)

Jones, S.A.

1994-01-01

Magnesium oxide will be used as a neutralizing agent for acidic plutonium-containing solutions. It is expected that as the magnesium oxide dissolves, the pH of the solution will rise, and plutonium will precipitate. The resulting solid will be tested for suitability to storage. The liquid is expected to contain plutonium levels that meet disposal limit requirements

Treatment of attention deficit hyperactivity disorder with monoamine amino acid precursors and organic cation transporter assay interpretation

Directory of Open Access Journals (Sweden)

Marty Hinz

2011-01-01

Full Text Available Marty Hinz1, Alvin Stein2, Robert Neff3, Robert Weinberg4, Thomas Uncini51NeuroResearch Clinics Inc, Cape Coral, FL; 2Stein Orthopedic Associates, Plantation, FL; 3Mental Training Inc, Dallas, TX; 4Department of Kinesiology and Health, Miami University, Oxford, OH; 5Laboratory, Fairview Regional Medical Center-Mesabi, Hibbing, MN, USABackground: This paper documents a retrospective pilot study of a novel approach for treating attention deficit hyperactivity disorder (ADHD with amino acid precursors of serotonin and dopamine in conjunction with urinary monoamine assays subjected to organic cation transporter (OCT functional status determination. The goal of this research was to document the findings and related considerations of a retrospective chart review study designed to identify issues and areas of concern that will define parameters for a prospective controlled study.Methods: This study included 85 patients, aged 4–18 years, who were treated with a novel amino acid precursor protocol. Their clinical course during the first 8–10 weeks of treatment was analyzed retrospectively. The study team consisted of PhD clinical psychologists, individuals compiling clinical data from records, and a statistician. The patients had been treated with a predefined protocol for administering amino acid precursors of serotonin and dopamine, along with OCT assay interpretation as indicated.Results: In total, 67% of participants achieved significant improvement with only amino acid precursors of serotonin and dopamine. In patients who achieved no significant relief of symptoms with only amino acid precursors, OCT assay interpretation was utilized. In this subgroup, 30.3% achieved significant relief following two or three urine assays and dosage changes as recommended by the assay results. The total percentage of patients showing significant improvement was 77%.Conclusion: The efficacy of this novel protocol appears superior to some ADHD prescription drugs

Aerosol and precipitation chemistry in the southwestern United States: spatiotemporal trends and interrelationships

Science.gov (United States)

Sorooshian, A.; Shingler, T.; Harpold, A.; Feagles, C. W.; Meixner, T.; Brooks, P. D.

2013-01-01

This study characterizes the spatial and temporal patterns of aerosol and precipitation composition at six sites across the United States Southwest between 1995 and 2010. Precipitation accumulation occurs mostly during the wintertime (December–February) and during the monsoon season (July–September). Rain and snow pH levels are usually between 5–6, with crustal-derived species playing a major role in acid neutralization. These species (Ca2+, Mg2+, K+, Na+) exhibit their highest concentrations between March and June in both PM2.5 and precipitation due mostly to dust. Crustal-derived species concentrations in precipitation exhibit positive relationships with SO42−, NO3−, and Cl–, suggesting that acidic gases likely react with and partition to either crustal particles or hydrometeors enriched with crustal constituents. Concentrations of particulate SO42− show a statistically significant correlation with rain SO42− unlike snow SO42−, which may be related to some combination of the vertical distribution of SO42− (and precursors) and the varying degree to which SO42−-enriched particles act as cloud condensation nuclei versus ice nuclei in the region. The coarse : fine aerosol mass ratio was correlated with crustal species concentrations in snow unlike rain, suggestive of a preferential role of coarse particles (mainly dust) as ice nuclei in the region. Precipitation NO3− : SO42− ratios exhibit the following features with potential explanations discussed: (i) they are higher in precipitation as compared to PM2.5; (ii) they exhibit the opposite annual cycle compared to particulate NO3− : SO42− ratios; and (iii) they are higher in snow relative to rain during the wintertime. Long-term trend analysis for the monsoon season shows that the NO3− : SO42− ratio in rain increased at the majority of sites due mostly to air pollution regulations of SO42− precursors. PMID:24432030

Aerosol and precipitation chemistry in the southwestern United States: spatiotemporal trends and interrelationships

Directory of Open Access Journals (Sweden)

A. Sorooshian

2013-08-01

Full Text Available This study characterizes the spatial and temporal patterns of aerosol and precipitation composition at six sites across the United States Southwest between 1995 and 2010. Precipitation accumulation occurs mostly during the wintertime (December–February and during the monsoon season (July–September. Rain and snow pH levels are usually between 5–6, with crustal-derived species playing a major role in acid neutralization. These species (Ca2+, Mg2+, K+, Na+ exhibit their highest concentrations between March and June in both PM2.5 and precipitation due mostly to dust. Crustal-derived species concentrations in precipitation exhibit positive relationships with SO42−, NO3−, and Cl−, suggesting that acidic gases likely react with and partition to either crustal particles or hydrometeors enriched with crustal constituents. Concentrations of particulate SO42− show a statistically significant correlation with rain SO42− unlike snow SO42−, which may be related to some combination of the vertical distribution of SO42− (and precursors and the varying degree to which SO42−-enriched particles act as cloud condensation nuclei versus ice nuclei in the region. The coarse : fine aerosol mass ratio was correlated with crustal species concentrations in snow unlike rain, suggestive of a preferential role of coarse particles (mainly dust as ice nuclei in the region. Precipitation NO3− : SO42− ratios exhibit the following features with potential explanations discussed: (i they are higher in precipitation as compared to PM2.5; (ii they exhibit the opposite annual cycle compared to particulate NO3− : SO42− ratios; and (iii they are higher in snow relative to rain during the wintertime. Long-term trend analysis for the monsoon season shows that the NO3− : SO42− ratio in rain increased at the majority of sites due mostly to air pollution regulations of SO42− precursors.

Dose-response functions for effects of acidic precipitation on vegetation

Energy Technology Data Exchange (ETDEWEB)

Jacobson, J S; Troiano, J J

1983-01-01

Research on the effect of sulfuric and nitric acids, as well as other substances, in rain on plant growth has focused on quantifying the relationship between doses of acids in precipitation and plant response. After eight years, there has been no direct demonstration of harmful effects to plants by ambient acidic rain in North America, and there remains considerable uncertainty about the potential risk to cultivated and native plants. Current efforts to describe the relationships between dose of acidity and effects on plants need better experimental approaches if the results are to be more relevant to actual field situations. Mechanistic models that describe the physiological and biochemical basis for effects of acidic rain on plants will be needed to provide confidence in the predictions of plant response. 34 references, 1 figure.

Biomediated Precipitation of Calcium Carbonate in a Slightly Acidic Hot Spring

Science.gov (United States)

Jiang, L.

2015-12-01

A slightly acidic hot spring named "Female Tower" (T=73.5 °C, pH=6.64) is located in the Jifei Geothermal Field, Yunnan Province, Southwest China. The precipitates in the hot spring are composed of large amounts of calcite, aragonite, and sulfur. Scanning electron microscopy (SEM) analyses revealed that the microbial mats were formed of various coccoid, rod-shaped, and filamentous microbes. Transmission electron microscopy (TEM) showed that the intracellular sulfur granules were commonly associated with these microbes. A culture-independent molecular phylogenetic analysis demonstrated that the majority of the bacteria in the spring were sulfur-oxidizing bacteria. In the spring water, H2S concentration was up to 60 ppm, while SO42- concentration was only about 10 ppm. We speculated that H2S might be utilized by sulfur-oxidizing bacteria in this hot spring water, leading to the intracellular formation of sulfur granules. In the meantime, this reaction increased the pH in the micron-scale microdomains, which fostered the precipitation of calcium carbonate in the microbial mats. The results of this study indicated that the sulfur-oxidizing bacteria could play an important role in calcium carbonate precipitation in slightly acidic hot spring environments.

On the Relation between Natural and Enforced Syneresis of Acidic Precipitated Silica

Directory of Open Access Journals (Sweden)

Sebastian Wilhelm

2014-11-01

Full Text Available Silica in industrial production processes is precipitated by mixing an acid and an inorganic precursor. In this aqueous solution, silica particles form due to a polymerization reaction and agglomeration and, finally, build a gel. Thereafter, the reaction continues, and the gel network shrinks with the expulsion of the enclosed pore liquid. This slow process is known as “natural syneresis” and strongly affects the product properties, such as the agglomerate size, specific surface or porosity of the silica produced. In order to investigate the influence of process parameters, such as temperature, pH or ionic strength, on the shrinkage in shorter time-scales, we propose an acceleration of this process and define it as “enforced syneresis”. The acceleration is performed by applying a mechanical external force to the gel by means of a plunger and measuring the shrinkage behavior under these conditions. Thereby, the conceptual idea is the prediction of the shrinkage due to natural syneresis based on the results of enforced syneresis. We are now able to predict the natural syneresis behavior from enforced syneresis data by the development of a correlative model. Using this prediction model, we can show the influence of temperature on the maximum shrinkage and on its rate in a significantly shorter time of about 12 h instead of several days.

Ceria powders by homogeneous precipitation technique

International Nuclear Information System (INIS)

Ramanathan, S.; Roy, S.K.

2003-01-01

Formation of precursors for ceria by two homogeneous precipitation reactions - (cerium chloride + urea at 95 degC - called reaction A and cerium chloride + hexamethylenetetramine at 85 degC - called reaction B) - has been studied. The variation of size of the colloidal particles formed and the zeta potential of the suspensions with progress of reactions exhibited similar trends for both the precipitation processes. Particle size increased from 100 to 300 nm with increasing temperature and extent of reaction. The zeta potential was found to decrease with increasing extent of precipitation in the pH range of 5 to 7. Filtration and drying led to agglomeration of the fine particles in case of the precursor from reaction B. The as-formed precursors were crystalline - a basic carbonate in case of reaction A and hydrous oxide in case of reaction B. It was found that nano-crystalline ceria powders (average crystallite size -10 nm) formed above 400 degC from both these precursors. The agglomerate size (D50) of the precursors and ceria powders formed after calcination at 600 degC varied from 0.7 to 3 μm. Increasing calcination temperature up to 800 degC, increased the crystallite size (50 nm). The zeta potential variation with pH and concentration of an anionic dispersant (Calgon) for the ceria powders formed was studied to determine the ideal conditions for suspension stability. It was found to be maximum (i.e., the suspensions stable) in the pH range of 3 to 4 or Calgon concentration of 0.01 to 0.1 weight percent. (author)

Detection and formation scenario of citric acid, pyruvic acid, and other possible metabolism precursors in carbonaceous meteorites

Science.gov (United States)

Cooper, George; Reed, Chris; Nguyen, Dang; Carter, Malika; Wang, Yi

2011-01-01

Carbonaceous meteorites deliver a variety of organic compounds to Earth that may have played a role in the origin and/or evolution of biochemical pathways. Some apparently ancient and critical metabolic processes require several compounds, some of which are relatively labile such as keto acids. Therefore, a prebiotic setting for any such individual process would have required either a continuous distant source for the entire suite of intact precursor molecules and/or an energetic and compact local synthesis, particularly of the more fragile members. To date, compounds such as pyruvic acid, oxaloacetic acid, citric acid, isocitric acid, and α-ketoglutaric acid (all members of the citric acid cycle) have not been identified in extraterrestrial sources or, as a group, as part of a “one pot” suite of compounds synthesized under plausibly prebiotic conditions. We have identified these compounds and others in carbonaceous meteorites and/or as low temperature (laboratory) reaction products of pyruvic acid. In meteorites, we observe many as part of three newly reported classes of compounds: keto acids (pyruvic acid and homologs), hydroxy tricarboxylic acids (citric acid and homologs), and tricarboxylic acids. Laboratory syntheses using 13C-labeled reactants demonstrate that one compound alone, pyruvic acid, can produce several (nonenzymatic) members of the citric acid cycle including oxaloacetic acid. The isotopic composition of some of the meteoritic keto acids points to interstellar or presolar origins, indicating that such compounds might also exist in other planetary systems. PMID:21825143

An integrated scheme for the simultaneous determination of biogenic amines, precursor amino acids, and related metabolites by liquid chromatography with electrochemical detection.

Science.gov (United States)

Oka, K; Kojima, K; Togari, A; Nagatsu, T; Kiss, B

1984-06-08

A new method using high-performance liquid chromatography with electrochemical detection (HPLC-ED) for the simultaneous determination of monoamines, their precursor amino acids, and related major metabolites in small samples of brain tissue weighing from 0.5 to 50 mg is described. The method is based on the preliminary isolation of monoamines (dopamine, norepinephrine, epinephrine, and serotonin), their precursor amino acids (tyrosine, 3,4-dihydroxyphenylalanine, tryptophan and 5-hydroxytryptophan), and their major metabolites (3-methoxytyramine, normetanephrine, 3,4-dihydroxyphenylacetic acid, homovanillic acid, vanillylmandelic acid, 3-methoxy-4-hydroxyphenylethyleneglycol, and 5-hydroxyindoleacetic acid) by chromatography on small columns of Amberlite CG-50 and Dowex 50W, and by ethyl acetate extraction. All the compounds in the four isolated fractions were measured by HPLC-ED on a reversed-phase column under four different conditions. The sensitivity was from 0.1 to 40 pmol, depending on the substances analysed. This newly established method was applied to the study of the effects of an aromatic L-amino acid decarboxylase inhibitor (NSD-1015) and a monoamine oxidase inhibitor (pargyline) on the levels of monoamines, their precursor amino acids and their major metabolites in brain regions of mice.

Polyfluorinated and perfluorinated chemicals in precipitation and runoff from cities across eastern and central China.

Science.gov (United States)

Zhao, Lijie; Zhou, Meng; Zhang, Tao; Sun, Hongwen

2013-02-01

Twenty-three polychlorinated and perfluorinated compounds (PFCs) were investigated in water phase and particulate matters of 19 precipitation samples (18 snow samples and 1 rain sample) from different cities across eastern and central China collected in February 2010. The PFCs in samples of 9e precipitation events during more than half a year at 1 site in Tianjin and 6 successive samples during 1 precipitation event were measured to elucidate the change of PFC in precipitation. In addition, PFCs in 3 runoffs at different kinds of sites in Tianjin were compared with those in the corresponding precipitation. The results showed that the particulate matters separated from the precipitation contained undetectable PFCs. The total PFC concentration ranged between 4.7 and 152 ng L(-1) in water phase of the precipitation samples, with perfluorooctanoic acid (PFOA) being detected at all of the sampling sites and the dominant PFC at most of the sampling sites. Some potential precursors of environmentally concerned PFCs and their degradation intermediates were measured simultaneously, among which 6:2 fluorotelomer unsaturated carboxylic acid (6:2 FTUCA), 8:2 FTUCA, and  × (3, 4, 5, 7):3 acid [F(CF(2))xCH(2)CH(2)COOH] were measured for the first time in Chinese precipitations; however, their concentrations were all lower than the limits of detection except that 6:2 FTUCA and 8:2 FTUCA could be detected in 3 and 8 precipitation samples, respectively. No clear seasonal variation in PFC concentrations in precipitation was observed during half a year; however, a relatively greater average concentration of total PFCs was observed during winter and summer compared with spring. The concentration of individual PFCs showed an obvious descending trend in the successive samples of the precipitation event. PFOA and perfluorononanoic acid in runoffs collected from different sites showed the following similar pattern-gas station > highway > university campus-whereas the other

Participation of the Pennsylvania State University in the MAP3S precipitation chemistry network

International Nuclear Information System (INIS)

Lamb, D.; de Pena, R.G.

1991-04-01

The Meteorology Department of the Pennsylvania State University collected precipitation in central Pennsylvania for more than 14 years on behalf of the Multistate Atmospheric Power Production Pollution Study (MAP3S). The MAP3S protocol, based on the sampling of precipitation from individual meteorological events over a long period of time, has allowed both for the development of a chemical climatology of precipitation in the eastern region of the United States and for a vastly improved understanding of the atmospheric processes responsible for wet acidic deposition. The precipitation chemistry data from the Penn State MAP3S site provide evidence of links to the anthropogenic emissions of sulfur dioxide and oxidant precursors. There is now little doubt that the free acidity in the precipitation of the region is due to the presence of unneutralized sulfate in the aqueous phase. In the absence of significant sources of this sulfur species and in view of supplemental enrichment studies, it is concluded that the sulfate enters cloud and rain water primarily through the aqueous-phase oxidation of sulfur dioxide emitted into the air within the geographical region of deposition. Within the source region the local abundances of sulfur dioxide often exceed those of the oxidants, so the depositions of sulfate and free acidity tend to be modulated by the availability of the strong oxidants. As a consequence, the deposition of sulfate exhibits a very strong seasonal dependence and little response to changes in the emissions of sulfur dioxide

OCHRE PRECIPITATES AND ACID MINE DRAINAGE IN A MINE ENVIRONMENT

Directory of Open Access Journals (Sweden)

BRANISLAV MÁŠA

2012-03-01

Full Text Available This paper is focused to characterize the ochre precipitates and the mine water effluents of some old mine adits and settling pits after mining of polymetallic ores in Slovakia. It was shown that the mine water effluents from two different types of deposits (adits; settling pits have similar composition and represent slightly acidic sulphate water (pH in range 5.60-6.05, sulphate concentration from 1160 to 1905 g.dm-3. The ochreous precipitates were characterized by methods of X-ray diffraction analysis (XRD, scanning electron microscopy (SEM and B.E.T. method for measuring the specific surface area and porosity. The dominant phases were ferrihydrite with goethite or goethite with lepidocrocide.

Improved method for measuring transparent exopolymer particles (TEP) and their precursors infresh and saline water

KAUST Repository

Villacorte, Loreen O.

2015-03-01

Transparent exopolymer particles (TEP) and their precursors produced by phyto-/bacterio-planktons in fresh and marine aquatic environments are increasingly considered as a major contributor to organic/particulate and biological fouling in micro-/ultra-filtration and reverse osmosis membrane (RO) systems. However, currently established methods which are based on Alcian blue (AB) staining and spectrophotometric techniques do not measure TEP-precursors and have the tendency to overestimate concentration in brackish/saline water samples due to interference of salinity on AB staining. Here we propose a new semi-quantitative method which allows measurement of both TEP and their colloidal precursors without the interference of salinity. TEP and their precursors are first retained on 10kDa membrane, rinsed with ultra-pure water, and re-suspended in ultra-pure water by sonication and stained with AB, followed by exclusion of TEP-AB precipitates by filtration and absorbance measurement of residual AB. The concentration is then determined based on the reduction of AB absorbance due to reaction with acidic polysaccharides, blank correction and calibration with Xanthan gum standard. The extraction procedure allows concentration of TEP and their pre-cursors which makes it possible to analyse samples with a wide range of concentrations (down to <0.1mg Xeq/L). This was demonstrated through application of the method for monitoring these compounds in algal cultures and a full-scale RO plant. The monitoring also revealed that concentrations of the colloidal precursors were substantially higher than the concentration of TEP themselves. In the RO plant, complete TEP removal was observed over the pre-treatment processes (coagulation-sedimentation-filtration and ultrafiltration) but the TEP precursors were not completely removed, emphasising the importance of measuring this colloidal component to better understand the role of TEP and acidic polysaccharides in RO membrane fouling.

Nanostructured barium titanate thin films from nanoparticles obtained by an emulsion precipitation method

NARCIS (Netherlands)

Woudenberg, F.C.M.; Sager, W.F.C.; ten Elshof, Johan E.; Verweij, H.

2005-01-01

Spherical non-agglomerated BaTiO3 precursor particles of 3–5 nm size were prepared by an emulsion precipitation method that consisted of the complexation of Ba- and Ti-precursors in separate water-in-decane emulsions, followed by mixing and controlled precipitation upon reactive decomposition of

Sol-gel precursors and products thereof

Science.gov (United States)

Warren, Scott C.; DiSalvo, Jr., Francis J.; Weisner, Ulrich B.

2017-02-14

The present invention provides a generalizable single-source sol-gel precursor capable of introducing a wide range of functionalities to metal oxides such as silica. The sol-gel precursor facilitates a one-molecule, one-step approach to the synthesis of metal-silica hybrids with combinations of biological, catalytic, magnetic, and optical functionalities. The single-source precursor also provides a flexible route for simultaneously incorporating functional species of many different types. The ligands employed for functionalizing the metal oxides are derived from a library of amino acids, hydroxy acids, or peptides and a silicon alkoxide, allowing many biological functionalities to be built into silica hybrids. The ligands can coordinate with a wide range of metals via a carboxylic acid, thereby allowing direct incorporation of inorganic functionalities from across the periodic table. Using the single-source precursor a wide range of functionalized nanostructures such as monolith structures, mesostructures, multiple metal gradient mesostructures and Stober-type nanoparticles can be synthesized. ##STR00001##

Dissolution of oxalate precipitate and destruction of oxalate ion by hydrogen peroxide in nitric acid solution

International Nuclear Information System (INIS)

Kim, Eung-Ho; Chung, Dong-Yong; Park, Jin-Ho; Yoo, Jae-Hyung

2000-01-01

This study aims at developing an oxalate precipitation process, which is applicable to a partitioning of long-lived radionuclides from the high-level radioactive liquid waste. In order to achieve this, a study for decomposition-reaction of oxalic acid by hydrogen peroxide was first carried out. The decomposition rates of H 2 O 2 and oxalic acid increased with an increase of nitric acid concentration, and especially those decomposition rates steeply increased at more than 2 M HNO 3 . Based on this result, the decomposition kinetics of H 2 O 2 and oxalic acid were suggested in this work. Then, the dissolution of oxalate precipitate and the destruction of oxalate ion in the solution were examined. Oxalate precipitates were prepared by adding oxalic acid into a simulated radioactive waste containing 8 metallic elements. The precipitates obtained thereby were dissolved in various nitric acid concentrations and reacted with H 2 O 2 at 90degC. When the oxalates were completely dissolved, most of the oxalates were decomposed by adding H 2 O 2 , but in a slurry state the decomposition yield of the oxalate decreased with an increase of the slurry density in the solution. Such phenomenon was considered to be due to a catalytic decomposition of H 2 O 2 on a solid surface of oxalate and the decomposition mechanism was explained by a charge transfer from a surface of oxalate solid to H 2 O 2 , producing OH radicals which can destruct H 2 O 2 explosively. Accordingly, the experimental condition for the decomposition of the oxalate precipitates was found to be most favorable at 3 M HNO 3 under the initial concentrations of 0.2 M oxalate and 1 M H 2 O 2 . At 3M HNO 3 , oxalate precipitates could be safely and completely dissolved, and almost decomposed. Additionally, it was observed that the presence of ferric ion in the solution largely affects the decomposition rate of H 2 O 2 . This could be explained by a chain reaction of hydrogen peroxide with ferric ion in the solution

Synthesis of hydroxyapatite with the use of calcium carbonate as of the biological precursor

International Nuclear Information System (INIS)

Aguilar, M.S.; Di Lello, B.C.; Queiroz, F.; Campos, N.C.; Campos, J.B.

2014-01-01

This work describes the synthesis of hydroxyapatite from calcium from biological materials such as shells carbonate. In the syntheses performed, the calcium carbonate of biological origin was used as the precursor and through a precipitation reaction with phosphoric acid, was converted into calcium hydroxide. Sequentially, the precipitate was aged, filtered, washed, dried and calcined, and then transformed into hydroxyapatite. The characterization of the powders was performed by X-DR (X-ray diffraction) and SEM (scanning electron microscopy). DR-X as determined hydroxyapatite calcium phosphate phase calcium. SEM revealed a morphology of finely divided particles. The method B.E.T. showed values of specific area and volume of micropores consistent with the literature. The results of the characterizations proved feasible to use for obtaining biological hydroxyapatite materials used in the reaction conditions.(author)

Thermal decomposition behavior of the co-precipitated carbonate precursor for La0.84Sr0.16MnO3

International Nuclear Information System (INIS)

Sankaranarayanan, A.; Kalekar, B.B.; Ramanathan, S.

2004-01-01

A carbonate precursor for lanthanum strontium manganite powder (La 0.84 Sr 0.16 MnO 3 - LSM) was obtained by addition of an aqueous solution of nitrates of lanthanum, strontium and manganese into a bath of ammonium carbonate solution. The precipitate was filtered, washed, dried and dry ground for homogenization. The thermal decomposition behavior of the precursor was studied by simultaneous TG-DTA-EGA technique while the precursor and intermediates formed at different temperatures were characterized by FTIR and XRD techniques for decomposition of carbonate and compound formation. It exhibited a loss in weight and endotherms in stages in the temperature ranges of 20 to 260 deg C, 260 deg to 500 deg C, 500 deg to 600 deg C, 600 deg to 900 deg C. The loss of carbon dioxide was exhibited in the EGA data and FTIR spectra while phase formation was confirmed by XRD. A comparative study of all these results showed that the processes occurring at various temperature ranges (20 deg to 260 deg C, 260 deg to 500 deg C, 500 deg to 600 deg C, 600 deg to 900 deg C) are dehydration of adsorbed moisture and water of crystallization, decomposition of manganese hydroxycarbonate to manganese dioxide, lanthanum carbonate to lanthanum oxy-carbonate and interaction between lanthanum oxy-carbonate, manganese dioxide and strontium carbonate to form finally LSM. Even though decomposition of carbonates into oxides was complete at 900 deg C, phase pure compound formation occurred at 1100 deg C, under the conditions used. (author)

Phase pure synthesis of BiFeO3 nanopowders using diverse precursor via co-precipitation method

International Nuclear Information System (INIS)

Shami, M. Yasin; Awan, M.S.; Anis-ur-Rehman, M.

2011-01-01

Highlights: → Synthesized phase pure BiFeO 3 using diverse precursor by co-precipitation method. → Optimized synthesis and processing parameters. → Thermal behavior, structure and microstructure were analyzed. → Resistivity vs temperature and dielectric constant vs frequency were measured. → Multiferroicity at room temperature was confirmed by M-H and P-E loops. - Abstract: Amorphous powder of BiFeO 3 (BFO) was synthesized at low-temperature (80 deg. C) by co-precipitation method. Optimal synthesis conditions for phase pure BFO were obtained. Powders were calcined in the temperature range from 400 to 600 deg. C for 1 h. Iso-statically pressed powder was sintered at 500 deg. C for 2 h. Differential scanning calorimetric thermo-gram guided for phase transition, crystallization and melting temperatures. X-ray diffraction confirmed the amorphous nature of as synthesized powder and phase formation of calcined powders. Calcination at temperature ≥400 deg. C resulted in nano crystalline powders with perovskite structure. Average crystallite size increased with the increase in calcination temperature. Scanning electron microscopic studies revealed dense granular microstructure of the sintered samples. The sintered samples exhibited high dc resistivity at room temperature which decreased with the increase in temperature. Dielectric constant, dielectric loss tangent and ac conductivity measurements were carried out in the frequency range (10 Hz to 2 MHz). The samples responded weak electric and magnetic polarization at room temperature with unsaturated and hysteresis free loops, respectively.

Formation of complex precursors of amino acids by irradiation of simulated interstellar media with heavy ions

Science.gov (United States)

Kobayashi, K.; Suzuki, N.; Taniuchi, T.; Kaneko, T.; Yoshida, S.

A wide variety of organic compounds have been detected in such extraterrestrial bodies as meteorites and comets Amino acids were identified in the extracts from Murchison meteorite and other carbonaceous chondrites It is hypothesized that these compounds are originally formed in ice mantles of interstellar dusts ISDs in molecular clouds by cosmic rays and ultraviolet light UV Formation of amino acid precursors by high energy protons or UV irradiation of simulated ISDs was reported by several groups The amino acid precursors were however not well-characterized We irradiated a frozen mixture of methanol ammonia and water with heavy ions to study possible organic compounds abiotically formed in molecular clouds by cosmic rays A mixture of methanol ammonia and water was irradiated with carbon beams 290 MeV u from a heavy ion accelerator HIMAC of National Institute of Radiological Sciences Japan Irradiation was performed either at room temperature liquid phase or at 77 K solid phase The products were characterized by gel filtration chromatography GFC FT-IR pyrolysis PY -GC MS etc Amino acids were analyzed by HPLC and GC MS after acid hydrolysis or the products Amino acids such as glycine and alanine were identified in the products in both the cases of liquid phase and solid phase irradiation Energy yields G-values of glycine were 0 014 liquid phase and 0 007 solid phase respectively Average molecular weights of the products were estimated as to 2300 in both the case Aromatic hydrocarbons N-containing heterocyclic

Acid precipitation and reproductive success of Ambystoma salamanders

Energy Technology Data Exchange (ETDEWEB)

Pough, R H; Wilson, R E

1976-01-01

The two species of mole salamander that occur in the Ithaca, New York, region (Ambystoma maculatum and A. jeffersonianum) breed in temporary ponds that are formed by accumulation of melted snow and spring rains. Water in many of these pools during the breeding season is acid; pH values as low as 3.5 have been measured. In laboratory experiments A. maculatum tolerated pHs from 6 to 10 and had greatest hatching success at pH 7 to 9. Ambystoma Jeffersonianum tolerated pH 4 to 8 and was most successful at pH 5 to 6. Mortality rose abruptly beyond the tolerance limits. The pH optimum shifted upward with increasing temperature for A. jeffersonianum and downward for A. maculatum. Judging from our laboratory studies, the acidity measured in breeding ponds should cause mortality in A. maculatum and permit normal development in A. jeffersonianum. In a four-year study of a large acidic vernal pond, 938 adult A. maculatum produced 486 metamorphosed juveniles (0.52 juvenile/adult), while 686 adult A. jeffersonianum produced 2157 juveniles (3.14 juveniles/adult). Because the effects of acid precipitation on the salamanders' breeding ponds are cumulative from year to year, profound changes in the salamander populations can be anticipated.

Acid precipitation and reproductive success of Ambystoma salamanders

Energy Technology Data Exchange (ETDEWEB)

Pough, F H; Wilson, R E

1977-03-01

The two species of mole salamander that occur in the Ithaca, New York, region (Ambystoma maculatum and A. jeffersonianum) breed in temporary ponds that are formed by accumulation of melted snow and spring rains. Water in many of these pools during the breeding season is acid; pH values as low as 3.5 have been measured. In laboratory experiments A. maculatum tolerated pHs from 6 to 10 and had greatest hatching success at pH 7 to 9. Ambystoma jeffersonianum tolerated pH 4 to 8 and was most successful at pH 5 to 6. Mortality rose abruptly beyond the tolerance limits. The pH optimum shifted upward with increasing temperature for A. jeffersonianum and downward for A. maculatum. Judging from our laboratory studies, the acidity measured in breeding ponds should cause mortality in A. maculatum and permit normal development in A. jeffersonianum. In a 4 yr study of a large, acidic vernal pond, 938 adult A. maculatum produced 486 metamorphosed juveniles (0.52 juvenile/adult), while 686 adult A. jeffersonianum produced 2157 juveniles (3.14 juveniles/adult). Because the effects of acid precipitation on the salamanders' breeding ponds are cumulative from year to year, profound changes in the salamander populations can be anticipated.

Formation of Amino Acid Precursors by Bombardment of Interstellar Ice Analogs with High Energy Heavy Ions

Science.gov (United States)

Kobayashi, Kensei; Mita, Hajime; Yoshida, Satoshi; Shibata, Hiromi; Enomoto, Shingo; Matsuda, Tomoyuki; Fukuda, Hitoshi; Kondo, Kotaro; Oguri, Yoshiyuki; Kebukawa, Yoko

2016-07-01

A wide variety of organic compounds have been detected in extraterrestrial bodies. It has been recognized that carbonaceous chondrites contain pristine amino acids [1]. There are several scenarios of the formation of such extraterrestrial amino acids or their precursors. Greenberg proposed a scenario that complex organic compounds were formed in interstellar ices in dense clouds, which were brought into solar system small bodies when the solar system was formed [2]. The ice mantles of interstellar dust particles (ISDs) in dense clouds are composed of H2O, CO, CH3OH, CH4, CO2, NH3, etc. In order to verify the scenario, a number of laboratory experiments have been conducted where interstellar ice analogs were irradiated with high-energy particles [3,4] or UV [5,6], and formation of complex organic compounds including amino acid precursors were detected in the products. Though ion-molecular reactions in gaseous phase and surface reactions on the ice mantles have been studied intensively, much less works on cosmic rays-induced reaction have been reported. In order to study possible formation of complex molecules in interstellar ices, frozen mixtures of water, methanol and ammonia with various mixing ratios were irradiated with high-energy heavy ions such as carbon ions (290 MeV/u) and neon ions (400 MeV/u) from HIMAC, NIRS, Japan. For comparison, gaseous mixtures of water, ammonia, carbon monoxide, carbon dioxide, and/or methane were irradiated with protons (2.5 MeV) from a Tandem accelerator, Tokyo Tech, Japan. Amino acids in the products were determined by cation exchange HPLC after acid hydrolysis. Products, both before and after acid hydrolysis, were also characterized by FT-IR and other techniques. Amino acids were detected in the hydrolyzed products after mixture of CH3OH, NH3 and H2O with various mixing ratios were irradiated with heavy ions, including when their mixing ratio was set close to the reported value of the interstellar ices (10:1:37). In the HIMAC

Thin HTSC films produced by a polymer metal precursor technique

Science.gov (United States)

Lampe, L. v.; Zygalsky, F.; Hinrichsen, G.

In precursors the metal ions are combined with acid groups of polymethacrylic acid (PMAA), polyacrylic acid (PAA) or novolac. Compared to thermal degradation temperature of pure polymers those of precursors are low. Precursors films were patterned by UV lithography. Diffractometric investigations showed that the c-axis oriented epitaxial films of YBa 2Cu 3O x and Bi 2Sr 2CaCu 2O x originated from amorphous metal oxide films, which were received after thermal degradation of the precursor. Transition temperatures and current densities were determined by electric resistivity measurements.

Effects of initial supersaturation on spontaneous precipitation of calcium carbonate in the presence of charged poly-L-amino acids.

Science.gov (United States)

Njegić-Dzakula, Branka; Falini, Giuseppe; Brecević, Ljerka; Skoko, Zeljko; Kralj, Damir

2010-03-15

Spontaneous precipitation of calcium carbonate was investigated in two precipitation systems: (1) with initial supersaturation lower than that corresponding to the solubility of amorphous calcium carbonate (ACC), at which vaterite precipitated, and (2) with initial supersaturation higher than that of ACC solubility, at which a mixture of calcite and vaterite was formed. After the addition of an acidic polypeptide, poly-L-glutamic acid (pGlu) or poly-L-aspartic acid (pAsp), into (1) a significant inhibition of nucleation, expressed as an increase in induction time, and growth of vaterite, perceived as a dead zone, was observed. Extent of inhibition decreased in the order: Inh(pAps)>Inh(pGlu)>Inh(pLys). The addition of a polypeptide into (2) caused the inhibition of precipitation and changed the morphology and polymorphic composition of the precipitate; only vaterite appeared at approximately c(pAsp)=3 ppm, c(pGlu)=6 ppm, or c(pLys)=7 ppm. This finding is explained as a consequence of kinetic constraints through the inhibition of calcite nucleation and stronger binding of acidic polypeptide by the calcite surfaces than by the vaterite surfaces. Laboratory precipitation studies using conditions that resemble those in living organism should be run at an initial supersaturation corresponding to the solubility of ACC as a limiting condition. 2009 Elsevier Inc. All rights reserved.

pH and its frequency distribution patterns of Acid Precipitation in Japan

International Nuclear Information System (INIS)

Kitamura, Moritsugu; Katou, Takunori; Sekiguchi, Kyoichi

1991-01-01

The pH data was collected at the 29 stations in Phase-I study of Acid Precipitation Survey over Japan by Japan Environment Agency in terms of frequency distribution patterns. This study was undertaken from April 1984 to March 1988, which was the first survey of acid precipitation over Japan with identical sampling procedures and subsequent chemical analyses. While the annual mean pH at each station ranged from 4.4 to 5.5, the monthly mean varied more widely, from 4.0 to 7.1. Its frequency distribution pattern was obtained for each station, and further grouped into four classes: class I; a mode at the rank of pH 4.5∼4.9, class II; bimodes above and below this pH region, class III; a mode at a higher pH region, class IV; a mode at a lower pH region. The bimodal pattern was suggestive of precipitation with and without incorporation of significant amounts of basic aerosol of anthropogenic origin during descent of rain droplet. The patterns of the stations were also classified on a basis of summer-winter difference into another four classes. Winter pH values were appreciably lower than summer pHs in western parts of Japan and on Japan Sea coast, we attribute the winter pH to probable contribution of acidic pollutants transported by strong winter monsoon from Eurasian Continent. At most stations in northern and eastern Japan, the pH was higher in winter months reflecting more incorporation of basic materials, e.g., NH 4 + and Ca 2+ . (author)

Oleic-acid-coated CoFe2O4 nanoparticles synthesized by co-precipitation and hydrothermal synthesis

International Nuclear Information System (INIS)

Gyergyek, Sašo; Drofenik, Miha; Makovec, Darko

2012-01-01

Highlights: ► Synthesis of oleic-acid-coated CoFe 2 O 4 nanoparticles from an aqueous solution. ► During the co-precipitation of Co 2+ /Fe 3+ single-phase spinel forms. ► During the co-precipitation of Co 2+ /Fe 2+ , feroxyhyte forms in addition to spinel. ► Oleic acid increases the spinel formation temperature and limits particle growth. ► Colloidal suspensions of ferrimagnetic CoFe 2 O 4 were prepared. - Abstract: Oleic-acid-coated CoFe 2 O 4 nanoparticles were synthesized by co-precipitation and hydrothermal synthesis. The coprecipitation of the nanoparticles was achieved by the rapid addition of a strong base to an aqueous solution of cations in the presence of the oleic acid surfactant, or without this additive. The nanoparticles were also synthesized by a hydrothermal treatment of suspensions of the precipitates, coprecipitated at room temperature in the presence of the oleic acid, or without it. The influence of the synthesis conditions, such as the valence state of the iron cation in the starting aqueous solution, the temperature of the treatment and the presence of oleic acid, on the particles size was systematically studied. X-ray powder diffractometry (XRD) and transmission electron microscopy (TEM) coupled with energy-dispersive X-ray spectroscopy (EDS) revealed that, although spinel forms at room temperature, a substantial amount of Co was incorporated within the secondary, feroxyhyte-like phase when the iron cation was in the 2+ state. In contrast, when iron was in the 3+ state, the spinel forms at elevated temperatures of approximately 60 °C. The presence of the oleic acid further increased the formation temperature for the stoichiometric spinel. Moreover, the oleic acid impeded the particles’ growth and enabled the preparation of colloidal suspensions of the nanoparticles in non-polar organic solvents. The nanoparticles’ size was successfully controlled by the temperature of the synthesis in the region where superparamagnetism

Activities and results of the terrestrial effects program: acid precipitation in Ontario study (Apios)

Energy Technology Data Exchange (ETDEWEB)

Linzon, S N

1986-11-01

Studies on the terrestrial effects of acidic precipitation in Ontario involve determining the effects on soils, crops, forests, lichens, mosses and biogeochemical systems. In the soils program, a baseline study was started in 1980 to establish a reliable and uniform data base for soils across the province, in order to identify future trends. Soil sensitivity criteria are being derived for mapping purposes. Starting in 1982, a complex, sophisticated mobile rain exclusion canopy system was constructed outdoors for controlled acid rain studies to determine the dose-response relationships of field crops. In response to numerous complaints a program was designed to determine the role that acidic precipitation is playing in the decline of sugar maple trees in Ontario. At 8 sites, tree conditions were noted, samples of foliage, bark, roots and soil were collected for chemical analysis, and increment cores and discs (from felled trees) were taken for radial growth patterns. Results from this study indicated that acidic precipitation was an additional stress to insect outbreaks and spring droughts. Intensive surveys have been conducted in selected areas in Ontario to identify the current viability and distribution of common denominator lichens and mosses. Biogeochemical studies are being conducted at four watersheds in Ontario. The different watersheds are located in progressively decreasing atmospheric deposition loadings from east to west across the province. The studies are attempting to document the role of contrasting terrestrial ecosystems in the process of lake acidification by atmospheric deposition. 9 references.

N-nitrosamine formation by monochloramine, free chlorine, and peracetic acid disinfection with presence of amine precursors in drinking water system.

Science.gov (United States)

West, Danielle M; Wu, Qihua; Donovan, Ariel; Shi, Honglan; Ma, Yinfa; Jiang, Hua; Wang, Jianmin

2016-06-01

In this study, the formation of eight N-nitrosamines, N-nitrosodimethylamine (NDMA), N-nitrosodiethylamine, N-nitrosomethylamine, N-nitrosodi-n-propylamine, N-nitrosodi-n-butylamine, N-Nitrosopiperidine, N-Nitrosopyrrolidine, N-Nitrosomorpholine, were systematically evaluated with respect to seven N-nitrosamine precursors (dimethylamine, trimethylamine, 3-(dimethylaminomethyl)indole, 4-dimethylaminoantipyrine, ethylmethylamine, diethylamine, dipropylamine) and three disinfectants (monochloramine, free chlorine, peracetic acid) under variable dosages, exposure times, and pH in a drinking water system. Without the presence of the seven selected N-nitrosamine precursors N-nitrosamine formation was not observed under any tested condition except very low levels of N-Nitrosopyrrolidine under some conditions. With selected N-nitrosamine precursors present N-nitrosamines formed at different levels under different conditions. The highest N-nitrosamine formation was NDMA with a maximum concentration of 1180 ng/L by monochloramine disinfection with precursors present; much lower levels of N-nitrosamines were formed by free chlorine disinfection; and no detectable level of N-nitrosamines were observed by peracetic acid disinfection except low level of N-Nitrosodi-n-propylamine under some conditions. NDMA formation was not affected by pH while four other N-nitrosamine formations were slightly affected by sample pH tested between 7 and 9, with formation decreasing with increasing pH. Monochloramine exposure time study displayed fast formation of N-nitrosamines, largely formed in four hours of exposure and maximized after seven days. This was a systematic study on the N-nitrosamine formation with the seven major N-nitrosamine precursors presence and absence under different conditions, including peracetic acid disinfection which has not been studied elsewhere. Copyright © 2016 Elsevier Ltd. All rights reserved.

Effects of precursors on the crystal structure and photoluminescence of CdS nanocrystalline

International Nuclear Information System (INIS)

Fu Zuoling; Zhou Shihong; Shi Jinsheng; Zhang Siyuan

2005-01-01

A series of cadmium sulfide (CdS) nanocrystalline were synthesized by precipitation from a mixture of aqueous solutions of cadmium salts and sulfur salts without adding any surface-termination agent. Their crystal structures and particle sizes were determined by X-ray diffraction (XRD). The CdS nanocrystalline precipitated from different precursors exhibited three cases: cubic phase, hexagonal phase and a hybrid of cubic and hexagonal phases. The photoluminescence (PL) of cadmium salt precursors and CdS nanocrystalline is also analyzed. Similar spectral band structure of cadmium salt precursors and CdS nanocrystalline is found. The PL of 3.4, 2.4 and 2.0 nm sized CdS nanocrystalline with the same crystal structure indicated quantum confinement effect

Phosphate recovery through struvite-family crystals precipitated in the presence of citric acid: mineralogical phase and morphology evaluation.

Science.gov (United States)

Perwitasari, D S; Edahwati, L; Sutiyono, S; Muryanto, S; Jamari, J; Bayuseno, A P

2017-11-01

Precipitation strategy of struvite-family crystals is presented in this paper to recover phosphate and potassium from a synthetic wastewater in the presence of citric acid at elevated temperature. The crystal-forming solutions were prepared from crystals of MgCl 2 and NH 4 H 2 PO 4 with a molar ratio of 1:1:1 for Mg +2 , [Formula: see text], and [Formula: see text], and the citric acid (C 6 H 8 O 7 ) was prepared (1.00 and 20.00 ppm) from citric acid crystals. The Rietveld analysis of X-ray powder diffraction pattern confirmed a mixed product of struvite, struvite-(K), and newberyite crystallized at 30°C in the absence of citric acid. In the presence of citric acid at 30° and 40°C, an abundance of struvite and struvite-(K) were observed. A minute impurity of sylvite and potassium peroxide was unexpectedly found in certain precipitates. The crystal solids have irregular flake-shaped morphology, as shown by scanning electron microscopy micrograph. All parameters (citric acid, temperature, pH, Mg/P, and N/P) were deliberately arranged to control struvite-family crystals precipitation.

Ochre precipitates and Acid Mine Drainage in a mine environment

Czech Academy of Sciences Publication Activity Database

Máša, B.; Pulišová, Petra; Bezdička, Petr; Michalková, E.; Šubrt, Jan

2012-01-01

Roč. 56, č. 1 (2012), s. 9-14 ISSN 0862-5468 R&D Projects: GA MŠk(CZ) MEB0810136 Grant - others:Ministry of Education of the Slovak Republic(SK) VEGA 1/0529/09 Institutional research plan: CEZ:AV0Z40320502 Keywords : ochre precipitate * Acid Mine Drainage (AMD) * X-ray diffraction analysis (XRD) * Scanning electron microscopy (SEM) * specific surface area and porosity Subject RIV: CA - Inorganic Chemistry Impact factor: 0.418, year: 2012

Conceptual design of a novel CO2 capture process based on precipitating amino acid solvents

NARCIS (Netherlands)

Sanchez Fernandez, E.; Heffernan, K.; Ham, L.V. van der; Linders, M.J.G.; Eggink, E.; Schrama, F.N.H.; Brilman, D.W.F.; Goetheer, E.L.V.; Vlugt, T.J.H.

2013-01-01

Amino acid salt based solvents can be used for CO2 removal from flue gas in a conventional absorption-thermal desorption process. Recently, new process concepts have been developed based on the precipitation of the amino acid zwitterion species during the absorption of CO2. In this work, a new

Nitric acid adduct formation during crystallization of barium and strontium nitrates and their co-precipitation from nitric acid media

International Nuclear Information System (INIS)

Mishina, N.E.; Zilberman, B.Ya.; Lumpov, A.A.; Koltsova, T.I.; Puzikov, E.A.; Ryabkov, D.V.

2015-01-01

The molar solubilities of Ba, Sr and Pb nitrates in nitric acid as a function of total nitrate concentration is presented and described by the mass action law, indicating on formation of the adducts with nitric acid. Precipitates of Ba(NO 3 ) 2 and Sr(NO 3 ) 2 crystallized from nitric acid were studied by ISP OES and IR spectroscopy. The data obtained confirmed formation of metastable adducts with nitric acid. IR and X-ray diffraction studies of the mixed salt systems indicated conversion of the mixed salts into (Ba,Sr)(NO 3 ) 2 solid solution of discrete structure in range of total nitrate ion concentration ∼6 mol/L. (author)

Radiochemical Means of Investigating Delayed Neutron Precursors

International Nuclear Information System (INIS)

Marmol, P. del

1968-01-01

Fast radiochemical methods used now for the determination of delayed neutron precursors are classified and reviewed: precipitations, solvent extractions, range experiments, milking, gas sweeping, isotopic and ion exchange, hot atom reactions and diffusion loss. Advantages and limitations of irradiation systems with respect to fast separations are discussed: external beams which allow faster separations only have low neutron fluxes, internal beams which are mostly fit for gaseous reactions; and rabbits for solution irradiations. Future prospects of radiochemical procedures are presented; among these, studies should be mostly oriented towards gaseous reactions which offer possibilities of isolating very short-lived delayed neutron precursors. Chemical procedures for delayed neutron precursor detection are compared with mass spectrometric and isotope separator techniques; it is concluded that the methods are complementary. (author)

Radiochemical Means of Investigating Delayed Neutron Precursors

International Nuclear Information System (INIS)

Marmol, P. del

1968-01-01

Fast radiochemical methods used now for the determination of delayed neutron precursors are classified and reviewed: precipitations, solvent extractions, range experiments, milking, gas sweeping, isotopic and ion exchange, hot-atom reactions and diffusion loss. Advantages and limitations of irradiation systems with respect to fast separations are discussed: external beams which allow faster separations only have low neutron fluxes, internal beams which are mostly fit for gaseous reactions; and rabbits for solution irradiations. Future prospects of radiochemical procedures are presented; among these, studies should be mostly oriented towards gaseous reactions which offer possibilities of isolating very short-lived delayed neutron precursors. Chemical procedures for delayed neutron precursor detection are compared with mass spectrometric and isotope-separator techniques; it is concluded that the methods are complementary. (author)

Comparison of Four Strong Acids on the Precipitation Potential of Gypsum in Brines During Distillation of Pretreated, Augmented Urine

Science.gov (United States)

Muirhead, Dean; Carrier, Christopher

2012-01-01

In this study, three different mineral acids were substituted for sulfuric acid (H2SO4) in the urine stabilizer solution to eliminate the excess of sulfate ions in pretreated urine and assess the impact on maximum water recovery to avoid precipitation of minerals during distillation. The study evaluated replacing 98% sulfuric acid with 85% phosphoric acid (H3PO4), 37% hydrochloric acid (HCl), or 70% nitric acid (HNO3). The effect of lowering the oxidizer concentration in the pretreatment formulation also was studied. This paper summarizes the test results, defines candidate formulations for further study, and specifies the injection masses required to stabilize urine and minimize the risk of mineral precipitation during distillation. In the first test with a brine ersatz acidified with different acids, the solubility of calcium in gypsum saturated solutions was measured. The solubility of gypsum was doubled in the brines acidified with the alternative acids compared to sulfuric acid. In a second series of tests, the alternative acid pretreatment concentrations were effective at preventing precipitation of gypsum and other minerals up to 85% water recovery from 95th-percentile pretreated, augmented urine. Based on test results, phosphoric acid is recommended as the safest alternative to sulfuric acid. It also is recommended that the injected mass concentration of chromium trioxide solution be reduced by 75% to minimize liquid resupply mass by about 50%, reduce toxicity of brines, and reduce the concentration of organic acids in distillate. The new stabilizer solution formulations and required doses to stabilize urine and prevent precipitation of minerals up to 85% water recovery are given. The formulations in this study were tested on a limited number of artificially augmented urine batches collected from employees at the Johnson Space Center (JSC). This study successfully demonstrated that the desired physical and chemical stability of pretreated urine and brines

Fermentation and purification strategies for the production of betulinic acid and its lupane-type precursors in Saccharomyces cerevisiae

DEFF Research Database (Denmark)

Czarnotta, Eik; Dianat, Mariam; Korf, Marcel

2017-01-01

from the bark of plane tree or birch. Here, we reengineered the reported betulinic acid pathway into S. cerevisiae and used this novel strain to develop efficient fermentation and product purification methods. Fed-batch cultivations with ethanol excess, using either an ethanol-pulse feed or controlling...... a constant ethanol concentration in the fermentation medium, significantly enhanced production of betulinic acid and its triterpenoid precursors. The beneficial effect of excess ethanol was further exploited in nitrogen-limited resting cell fermentations, yielding betulinic acid concentrations of 182 mg...

Calcium in milk products precipitates intestinal fatty acids and secondary bile acids and thus inhibits colonic cytotoxicity in humans

NARCIS (Netherlands)

Govers, MJAP; Termont, DSML; Lapre, JA; Kleibeuker, JH; Vonk, RJ; VanderMeer, R

1996-01-01

Dietary calcium may reduce the risk of colon cancer, probably by precipitating cytotoxic surfactants, such as secondary bile acids, in the colonic lumen. We previously showed that milk mineral, an important source of calcium, decreases metabolic risk factors and colonic proliferation in rats, We non

Mechanism of calcium phosphates precipitation in liquid crystals; Mecanisme de precipitation de phosphates de calcium dans des cristaux liquides

Energy Technology Data Exchange (ETDEWEB)

Prelot, B.; Zemb, T

2004-04-01

The possibility of using as a precursor an easily wet meso-porous powder would be a breakthrough in the preparation of nuclear waste storage ceramics. A concentrated solution containing ions to be stored would wet a dry powder and then, subjected to mild compression, lead to a micro-crystalline matrix of calcium phosphate at acceptable temperatures. Since no porous calcium phosphate different from calcined bone (patented) is described as porous precursor, we have compared the different synthesis routes towards meso-porous ceramics. First, we considered homogeneous precipitation of slats in water: using initially off-stoichiometry in reaction, micron-sized hydroxyapatite particles are produced with a specific surface up to 100 m{sup 2}/g. Then, we consider the classical route of precipitation of an hybrid material in the miscibility gap of a phase diagram, when an hexagonal liquid crystal is used a matrix for precipitation. The surfactant family consists in single chain surfactants containing phosphates as head-group to poison the growing surface of calcium phosphate nano-domains. Since the reaction is still too brutal, we considered using a cat-anionic precursor material of controllable surface charge. For certain concentrations and molar ratios, a new structure not yet described in surfactant precipitation literature is observed: since the periodicity is lower than twice the chain length, a disordered constant curvature monolayer (instead of the classical cylinder of twice chain length diameter) of surfactant is implied. Finally, we have investigated synthesis routes implying slow dissolution of pre-formed calcium phosphate in an already existing hexagonal matrix. For all these routes of synthesis, micro-structural determinations using SAXS, WARS and BET are performed, with a special attention to comparison of the precipitation material, the matrix obtained with all elements present, and also the material obtained after calcinations. (authors)

Bulk and Surface Structures of Palladium-Modified Copper-Zinc Oxides ex Hydroxycarbonate Precursors

NARCIS (Netherlands)

López Granados, M.; Melián-Cabrera, I.; Fierro, J.L.G.

2002-01-01

(Pd)-Cu-Zn ex hydroxycarbonate precursors were prepared and characterized by several bulk and surface techniques. A palladium-free Cu-Zn precursor (CZ) was prepared by coprecipitation. Two Pd-Cu-Zn samples were prepared by coprecipitation (PCZ-CP) and sequential precipitation (PCZ-SP). It is shown

Fatty acid cosubstrates provide β-oxidation precursors for rhamnolipid biosynthesis in Pseudomonas aeruginosa, as evidenced by isotope tracing and gene expression assays.

Science.gov (United States)

Zhang, Lin; Veres-Schalnat, Tracey A; Somogyi, Arpad; Pemberton, Jeanne E; Maier, Raina M

2012-12-01

Rhamnolipids have multiple potential applications as "green" surfactants for industry, remediation, and medicine. As a result, they have been intensively investigated to add to our understanding of their biosynthesis and improve yields. Several studies have noted that the addition of a fatty acid cosubstrate increases rhamnolipid yields, but a metabolic explanation has not been offered, partly because biosynthesis studies to date have used sugar or sugar derivatives as the carbon source. The objective of this study was to investigate the role of fatty acid cosubstrates in improving rhamnolipid biosynthesis. A combination of stable isotope tracing and gene expression assays was used to identify lipid precursors and potential lipid metabolic pathways used in rhamnolipid synthesis when fatty acid cosubstrates are present. To this end, we compared the rhamnolipids produced and their yields using either glucose alone or glucose and octadecanoic acid-d(35) as cosubstrates. Using a combination of sugar and fatty acids, the rhamnolipid yield was significantly higher (i.e., doubled) than when glucose was used alone. Two patterns of deuterium incorporation (either 1 or 15 deuterium atoms) in a single Rha-C(10) lipid chain were observed for octadecanoic acid-d(35) treatment, indicating that in the presence of a fatty acid cosubstrate, both de novo fatty acid synthesis and β-oxidation are used to provide lipid precursors for rhamnolipids. Gene expression assays showed a 200- to 600-fold increase in the expression of rhlA and rhlB rhamnolipid biosynthesis genes and a more modest increase of 3- to 4-fold of the fadA β-oxidation pathway gene when octadecanoic acid was present. Taken together, these results suggest that the simultaneous use of de novo fatty acid synthesis and β-oxidation pathways allows for higher production of lipid precursors, resulting in increased rhamnolipid yields.

Aroma Precursors in Grapes and Wine: Flavor Release during Wine Production and Consumption.

Science.gov (United States)

Parker, Mango; Capone, Dimitra L; Francis, I Leigh; Herderich, Markus J

2018-03-14

Pioneering investigations into precursors of fruity and floral flavors established the importance of terpenoid and C 13 -norisoprenoid glycosides to the flavor of aromatic wines. Nowadays flavor precursors in grapes and wine are known to be structurally diverse, encompassing glycosides, amino acid conjugates, odorless volatiles, hydroxycinnamic acids, and many others. Flavor precursors mainly originate in the grape berry but also from oak or other materials involved in winemaking. Flavors are released from precursors during crushing and subsequent production steps by enzymatic and nonenzymatic transformations, via microbial glycosidases, esterases, C-S lyases, and decarboxylases, and through acid-catalyzed hydrolysis and chemical rearrangements. Flavors can also be liberated from glycosides and amino acid conjugates by oral microbiota. Hence, it is increasingly likely that flavor precursors contribute to retronasal aroma formation through in-mouth release during consumption, prompting a shift in focus from identifying aroma precursors in grapes to understanding aroma precursors present in bottled wine.

Study of lithium extraction from brine water, Bledug Kuwu, Indonesia by the precipitation series of oxalic acid and carbonate sodium

Science.gov (United States)

Sulistiyono, Eko; Lalasari, Latifa Hanum; Mayangsari, W.; Prasetyo, A. B.

2018-05-01

Lithium is one of the key elements in the development of batteries for electric car applications. Currently, the resources of the world's lithium are derived from brine water and lithium mineral based on spodumene rock. Indonesia which is located in the area of the ring of fire, has potential brine water resources in some area, such as brine water from Bledug Kuwu, Central Java that used in this research. The purposes of this research are to characterize brine water, Bledug Kuwu and to investigate the influence of chemical solvents on Li, Na, K, Ca, Mg, Al, B ion precipitation from brine water. This research was done with 2 times the process of chemical precipitation that runs series as follows: 5 liters of brine water were chemically precipitated using 400 ml of 12.43 N oxalic acid and followed by chemical precipitation using 400 mL of 7.07 N sodium carbonate solutions. Evaporation and filtration processes were also done twice in an effort to separate white precipitate and filtrate. The filtrate was analyzed by ICP-OES and white precipitates (salts) were analyzed by SEM, XRD, and XRF. The result shows that oxalate precipitation process extracted 32.24% Al, 23.42% B, 22.43% Ca, 14.26% Fe, 3.21 % K, 9.86% Na and 14.26% Li, the following process by carbonate precipitation process extracted 98.86% Mg, 73% Ca, 22.53% Li, 82.04% Al, 14.38% B, 12.50% K, 2.27% Na. There is 63.21% lithium is not extracted from the series process. The SEM analysis shows that the structure of granules on the precipitated salts by oxalic acid form gentle cubic-shaped solid. In the other hand, oxalate precipitation followed by sodium carbonate has various particle sizes and the shape of crystals is fragments, prism and cube look like magnesium carbonate, calcium chloride, and calcite's crystal respectively. This is in accordance with XRD analysis that phases of whewellite (CaC2O4.H2O), disodium oxalate (Na2C2O4), magnesite (MgCO3), calcium lithium aluminum (Al1.19 Ca1Li0.81), dolomite (CaCO3

Sustained release of nucleic acids from polymeric nanoparticles using microemulsion precipitation in supercritical carbon dioxide.

Science.gov (United States)

Ge, Jun; Jacobson, Gunilla B; Lobovkina, Tatsiana; Holmberg, Krister; Zare, Richard N

2010-12-21

A general approach for producing biodegradable nanoparticles for sustained nucleic acid release is presented. The nanoparticles are produced by precipitating a water-in-oil microemulsion in supercritical CO(2). The microemulsion consists of a transfer RNA aqueous solution (water phase), dichloromethane containing poly(l-lactic acid)-poly(ethylene glycol) (oil phase), the surfactant n-octyl β-D-glucopyranoside, and the cosurfactant n-butanol.

Thermal behavior and phase transformation of ZrO2–10%SiO2 precursor powder prepared by a co-precipitation route without adding stability agent

International Nuclear Information System (INIS)

Chu, Hsueh-Liang; Hwang, Weng-Sing; Wang, Cheng-Li; Wang, Moo-Chin; Lee, Kuen-Chan; Huang, Hong-Hsin; Lee, Huey-Er

2014-01-01

Highlights: • The precursor powders contained about 68.3 wt% ZrO 2 , which corresponds to ZrO 2 ·1/8 H 2 O. • The exothermic peak temperature of tetragonal ZrO 2 formation occurred at 1014 K. • The activation energy of ZrO 2 –10%SiO 2 precursors crystallization is 993.7 kJ/mol. • Only the tetragonal ZrO 2 formed when the precursor calcined at 1173–1373 K for 2 h. • As calcined at 1473 K for 2 h, tetragonal ZrO 2 fully converted to monoclinic ZrO 2 . - Abstract: Thermal behavior and phase transformation of ZrO 2 –10%SiO 2 precursor powder prepared by a co-precipitation route without adding stability agent has been studied using different thermal analysis/thermogravimetry (DTA/TG), X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), nano beam electron diffraction (NBED), high-resolution TEM (HRTEM) and energy-dispersive X-ray spectrometer (EDS). The TG results show that four weight loss regions were from 298 to 443 K, 443 to 743 K, 743 to 793 K and 793 to 1400 K. The DTA result shows that the ZrO 2 freeze-dried precursor powders crystallization at 1014 K. The activation energy of 993.7 kJ/mol was obtained for tetragonal ZrO 2 crystallization using a non-isothermal process. The XRD result shows that only a single phase of tetragonal ZrO 2 appears when the freeze-dried precursor powders after calcination between 1173 and 1373 K for 2 h. Moreover, when calcined at 1473 K for 2 h, the phase transformation from tetragonal ZrO 2 fully converted to monoclinic ZrO 2 occurred

Preparation and Sintering Behaviour of Alumina Powder by Ammonia Precipitation Method

Directory of Open Access Journals (Sweden)

Wang Liuyan

2017-01-01

Full Text Available In this paper, alumina precursor was prepared by the ammonia precipitation method which used Al (NO3 3 9H2O as aluminum source and NH4OH as a precipitator, adding a small amount of PEG4000 as the surface active agent. Finally γ-Al2O3 was obtained at 900° for 2h. The stable alumina crystal form of α-Al2O3 was got at 1100° for 2h. The influence of precipitation agent on the precursor was studied by means of TG / DTA and Tem, XRD etc. The effects of the synthesis temperature and time on the phase composition and morphology of the alumina powder were also analysed.

The impacts of temperature, alcoholic degree and amino acids content on biogenic amines and their precursor amino acids content in red wine.

Science.gov (United States)

Lorenzo, C; Bordiga, M; Pérez-Álvarez, E P; Travaglia, F; Arlorio, M; Salinas, M R; Coïsson, J D; Garde-Cerdán, T

2017-09-01

The aim was to study how factors such as temperature, alcoholic degree, and amino acids supplementation are able to influence the content of tyramine, histamine, 2-phenylethylamine, tryptamine and their precursor amino acids in winemaking process. Biogenic amines and amino acids were quantified at the beginning, middle and end of alcoholic fermentation, and at the end of malolactic fermentation. In general, samples produced with amino acid supplementation did not show the highest concentrations of biogenic amines, except for histamine, which content increased with the addition of the four amino acids. The synthesis of tyramine was mainly affected by the temperature and alcoholic degree, the formation of phenylethylamine was largely influenced by alcoholic degree, and tryptamine synthesis principally depended on temperature. Interestingly, there was interaction between these three factors for the biogenic amines studied. In conclusion, winemaking conditions should be established depending on the biogenic amine which synthesis is required to be controlled. Copyright © 2017 Elsevier Ltd. All rights reserved.

A non-classical view of the modulation of mineral precipitation by organic additives

Science.gov (United States)

Ruiz-Agudo, Encarnacion; Ruiz-Agudo, Cristina; Burgos-Cara, Alejandro; Putnis, Christine; Rodriguez-Navarro, Carlos; Putnis, Andrew

2016-04-01

Questions persist on the mechanisms of crystallization of sparingly soluble minerals such as calcium carbonate, calcium oxalate or barium sulphate. Compared to CaCO3, the mechanisms of nucleation and growth in the CaC2O4-H2O or BaSO4-H2O systems have received less attention. These phases are important due to their relevance as biominerals and/or unwanted mineral deposits in technological applications. Growing evidence suggests that sparingly soluble salts form by non-classical nucleation and growth pathways, where pre-nucleation ion associates and amorphous (solid or liquid) precursor phase(s) play a critical role (e.g. Rodríguez-Navarro et al. (2015), Ruiz-Agudo et al. (2015)). Indeed the identification of pre-nucleation species in these systems and their strong interactions with organic compounds (Verch et al. 2011) raises the possibility that the control of organics on biomineralization may begin even earlier than previously thought. A sound knowledge of the physical mechanisms by which acidic macromolecules affect nucleation and early growth may offer general insights concerning the molecular control of biomineralization, as well as being critical for improving strategies to control unwanted mineral deposition or for the synthesis of biomimetic materials. Here we present investigations on the initial stages of the precipitation of these relevant minerals in organic-free solutions to identify the precipitation pathway and to look for any potential precursor phase(s) to the final, crystalline polymorph. As well, we explore the effects that several acidic organic compounds have on the different precipitation stages identified. We find that organic additives such as citric acid, polyacrilic acid or a commercial copolymer of maleic acid/allyl sulfonic acid with phosphonate groups can be active at modifying pre-nucleation stages (destabilizing of pre-nucleation species or hampering the aggregation and growth of pre-nucleation associates) and subsequently strongly

Mechanism of calcium phosphates precipitation in liquid crystals

International Nuclear Information System (INIS)

Prelot, B.; Zemb, T.

2004-04-01

The possibility of using as a precursor an easily wet meso-porous powder would be a breakthrough in the preparation of nuclear waste storage ceramics. A concentrated solution containing ions to be stored would wet a dry powder and then, subjected to mild compression, lead to a micro-crystalline matrix of calcium phosphate at acceptable temperatures. Since no porous calcium phosphate different from calcined bone (patented) is described as porous precursor, we have compared the different synthesis routes towards meso-porous ceramics. First, we considered homogeneous precipitation of slats in water: using initially off-stoichiometry in reaction, micron-sized hydroxyapatite particles are produced with a specific surface up to 100 m 2 /g. Then, we consider the classical route of precipitation of an hybrid material in the miscibility gap of a phase diagram, when an hexagonal liquid crystal is used a matrix for precipitation. The surfactant family consists in single chain surfactants containing phosphates as head-group to poison the growing surface of calcium phosphate nano-domains. Since the reaction is still too brutal, we considered using a cat-anionic precursor material of controllable surface charge. For certain concentrations and molar ratios, a new structure not yet described in surfactant precipitation literature is observed: since the periodicity is lower than twice the chain length, a disordered constant curvature monolayer (instead of the classical cylinder of twice chain length diameter) of surfactant is implied. Finally, we have investigated synthesis routes implying slow dissolution of pre-formed calcium phosphate in an already existing hexagonal matrix. For all these routes of synthesis, micro-structural determinations using SAXS, WARS and BET are performed, with a special attention to comparison of the precipitation material, the matrix obtained with all elements present, and also the material obtained after calcinations. (authors)

Acid deposition: State of science and technology. Summary report of the U.S. National Acid Precipitation Assessment Program

International Nuclear Information System (INIS)

Irving, P.M.; Smith, E.

1991-09-01

The twenty-seven State-of-Science and State-of-Technology (SOS/T) Reports, published in 1990 as the definitive scientific and technical synthesis of information obtained during the first decade of the U.S. national Acid Precipitation Assessment Program (NAPAP), are summarized in the document. In most cases, these summaries were the final chapter of the complete SOS/T Report

The production of rare earth elements group via tributyl phosphate extraction and precipitation stripping using oxalic acid

Directory of Open Access Journals (Sweden)

Esmaeil Jorjani

2016-11-01

Full Text Available In this study, solvent extraction and precipitation stripping were used to produce rare earth elements (REEs. Tributyl phosphate (TBP was used to extract yttrium, lanthanum, cerium, and neodymium from an aqueous solution produced by nitric acid leaching of apatite concentrate. In the extraction stage, the effects of TBP concentration, pH, contact time, temperature, and phase ratio were investigated. The results show that about 95%, 90%, 87% and 80% of neodymium, cerium, lanthanum, and yttrium, respectively, can be extracted in optimum conditions of extraction. Hot, deionized water was used to scrub the impurities from the loaded organic phase. The results showed that three stages of scrubbing with a phase ratio (Va/Vo of five removed about 80%, 30%, 27%, and 15% of Ca, Mg, Fe, and P, respectively, from loaded TBP, while less than 9% of total REEs was lost. The effects on precipitation stripping of oxalic acid concentration, contact time, and phase ratio were investigated. The results showed that precipitation stripping is a viable alternative to traditional acid stripping in the REEs production process. Mixed REEs oxide with an assay of about 90% can be achieved as a final product.

Formation of amino acid precursors in the Solar System small bodies using Aluminium-26 as an energy source

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Kebukawa, Yoko; Kobayashi, Kensei; Kawai, Jun; Mita, Hajime; Tachibana, Shogo; Yoda, Isao; Misawa, Shusuke

2016-07-01

Carbonaceous chondrites contain various organic matter including amino acids that may have played an important role for origin of life on the early Earth. The parent bodies of the chondritic meteorites likely formed from silicate dust grains containing some water ice and organic compounds. These planetesimals are known to contain short-lived radio isotopes such as ^{26}Al, and the heat generated from the decay of ^{26}Al was considered to be used for melting ice. The liquid water, for example, changed anhydrous silicates into hydrous silicates, i.e., aqueous alteration. The liquid water would act also as an ideal reaction medium for various organic chemistry. Cody et al. [1] proposed IOM formation via formose reaction starting with formaldehyde and glycolaldehyde during aqueous activity in the small bodies. Additional hydrothermal experiments showed that ammonia enhanced the yields of IOM like organic solids [2]. Formaldehyde and ammonia are ubiquitous in the Solar System and beyond, e.g., comets contain H _{2}CO : NH _{3} : H _{2}O = 0.4-4 : 0.5-1.5 : 100 [3]. Thus these molecules can be expected to have existed in some Solar System small bodies. We study the liquid phase chemistry of the formaldehyde and ammonia, including formations of amino acid precursor molecules, via hydrothermal experiments at isothermal temperatures of 90 °C to 200 °C. We also evaluate the effects of gamma-ray which is released from the decay of ^{26}Al with gamma-ray irradiation experiments using a ^{60}Co gamma-ray source at Tokyo Institute of Technology. Amino acids were detected mostly after acid hydrolysis of heated or irradiated solutions, indicating that most of the amino acids in the products exist as precursors. Some samples contained 'free' amino acids that were detected without acid hydrolysis, but much lower abundance than after acid hydrolysis. Kendrick mass defect (KMD) analyses of High resolution mass spectra obtained using ESI-MS revealed that various CHO and CHNO

Removal of chromophore in enzymatic hydrolysis by acid precipitation to improve the quality of xylo-oligosaccharides from corn stalk.

Science.gov (United States)

Wang, Yue-Hai; Zhang, Jie; Qu, Yong-Shui; Li, Hong-Qiang

2018-02-01

As the most representative functional sugar, the application areas and market demands of xylo-oligosaccharides (XOS) have been expanding year by year. Owing to the complex structure of corn stalk (CS), XOS obtained from CS are accompanied by problems such as low purity and high color value, which degrade the product. To improve the quality of XOS from CS, the enzymatic hydrolysis was precipitated by acid; then, the ethanol elution concentration was systematically investigated after optimizing the adsorption conditions. The results showed that the purity of XOS was increased to 87.28% from 67.31%, and the color value was decreased to 1050 from 4682 when the acid precipitation pH was 2. On the basis of acid precipitation, if the corresponding optimal conditions of XOS adsorption and elution were used, the highest purity of XOS was 97.87% obtained, with the lowest color value, 780, which reached the standard of the commercial XOS. Copyright © 2017. Published by Elsevier Ltd.

Synthesis, structural, morphological, optical and magnetic characterization of iron oxide (α-Fe2O3) nanoparticles by precipitation method: Effect of varying the nature of precursor

Science.gov (United States)

Lassoued, Abdelmajid; Lassoued, Mohamed Saber; Dkhil, Brahim; Ammar, Salah; Gadri, Abdellatif

2018-03-01

α-Fe2O3 nanoparticles were prepared via a precipitation method using each of three different precursors ((FeCl3, 6H2O), (Fe (C5H7O2)3) and (Fe (NO3)3, 9H2O)). The impact of varying the nature of the precursor on crystalline phase, size and magnetic parameters of α-Fe2O3 was examined. Powder X-ray diffraction pattern disclosed rhombohedral structure. The TEM and SEM results showed that the size of α-Fe2O3 nanocrystals was between 21 and 38 nm. FT-IR confirms the phase purity of prepared compounds. Raman studies showed the phonon modes. The TGA showed three mass losses, whereas DTA resulted in three endothermic peaks. The optical investigation exhibited that samples have an optical gap of 2.1 eV. The products exhibited the attractive magnetic properties with high saturation magnetization, which were examined by a vibrating sample magnetometer (VSM).

Application of a precipitation method for uranium recovery from Abu-Zaabal phosphoric acid plant, egypt

International Nuclear Information System (INIS)

El-Hazek, N.M.T.; Hussein, E.M.

1997-01-01

Current industrial recovery of uranium from 30% phosphoric acid-produced by the dihydrate process-is based on solvent extraction method. Uranium recovery from concentrated phosphoric acid (45-52% P 2 O 5 ) produced by evaporation of the 30% acid or directly produced by the hemihydrate process, by solvent extraction is difficult to apply in practice. In addition to possible contamination of the acid by the organic solvents and/or their deterioration. This paper investigates the possibility of applying a precipitation method (Weterings and Janssen, 1985) for uranium recovery from both low (28% P 2 O 2 ) and high (48% P 2 O 5 ) concentration phosphoric acids produced by abu-Zaabal phosphoric acid plant (abu-Zaabal fertilizers and chemicals Co., Egypt). The 28% acid produced by H 2 SO 4 dihydrate method and the 48% acid produced by evaporation of the 28% acid

Stable amorphous georgeite as a precursor to a high-activity catalyst

Science.gov (United States)

Kondrat, Simon A.; Smith, Paul J.; Wells, Peter P.; Chater, Philip A.; Carter, James H.; Morgan, David J.; Fiordaliso, Elisabetta M.; Wagner, Jakob B.; Davies, Thomas E.; Lu, Li; Bartley, Jonathan K.; Taylor, Stuart H.; Spencer, Michael S.; Kiely, Christopher J.; Kelly, Gordon J.; Park, Colin W.; Rosseinsky, Matthew J.; Hutchings, Graham J.

2016-03-01

Copper and zinc form an important group of hydroxycarbonate minerals that include zincian malachite, aurichalcite, rosasite and the exceptionally rare and unstable—and hence little known and largely ignored—georgeite. The first three of these minerals are widely used as catalyst precursors for the industrially important methanol-synthesis and low-temperature water-gas shift (LTS) reactions, with the choice of precursor phase strongly influencing the activity of the final catalyst. The preferred phase is usually zincian malachite. This is prepared by a co-precipitation method that involves the transient formation of georgeite; with few exceptions it uses sodium carbonate as the carbonate source, but this also introduces sodium ions—a potential catalyst poison. Here we show that supercritical antisolvent (SAS) precipitation using carbon dioxide (refs 13, 14), a process that exploits the high diffusion rates and solvation power of supercritical carbon dioxide to rapidly expand and supersaturate solutions, can be used to prepare copper/zinc hydroxycarbonate precursors with low sodium content. These include stable georgeite, which we find to be a precursor to highly active methanol-synthesis and superior LTS catalysts. Our findings highlight the value of advanced synthesis methods in accessing unusual mineral phases, and show that there is room for exploring improvements to established industrial catalysts.

2-Phenyl-tetrahydropyrimidine-4(1H-ones – cyclic benzaldehyde aminals as precursors for functionalised β2-amino acids

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Markus Nahrwold

2009-09-01

Full Text Available Novel procedures have been developed to condense benzaldehyde effectively with β-amino acid amides to cyclic benzyl aminals. Double carbamate protection of the heterocycle resulted in fully protected chiral β-alanine derivatives. These serve as universal precursors for the asymmetric synthesis of functionalised β2-amino acids containing acid-labile protected side chains. Diastereoselective alkylation of the tetrahydropyrimidinone is followed by a chemoselective two step degradation of the heterocycle to release the free β2-amino acid. In the course of this study, an L-asparagine derivative was condensed with benzaldehyde and subsequently converted to orthogonally protected (R-β2-homoaspartate.

Pimelic acid, the first precursor of the Bacillus subtilis biotin synthesis pathway, exists as the free acid and is assembled by fatty acid synthesis.

Science.gov (United States)

Manandhar, Miglena; Cronan, John E

2017-05-01

Biotin synthetic pathways are readily separated into two stages, synthesis of the seven carbon α, ω-dicarboxylic acid pimelate moiety and assembly of the fused heterocyclic rings. The biotin pathway genes responsible for pimelate moiety synthesis vary widely among bacteria whereas the ring synthesis genes are highly conserved. Bacillus subtilis seems to have redundant genes, bioI and bioW, for generation of the pimelate intermediate. Largely consistent with previous genetic studies it was found that deletion of bioW caused a biotin auxotrophic phenotype whereas deletion of bioI did not. BioW is a pimeloyl-CoA synthetase that converts pimelic acid to pimeloyl-CoA. The essentiality of BioW for biotin synthesis indicates that the free form of pimelic acid is an intermediate in biotin synthesis although this is not the case in E. coli. Since the origin of pimelic acid in Bacillus subtilis is unknown, 13 C-NMR studies were carried out to decipher the pathway for its generation. The data provided evidence for the role of free pimelate in biotin synthesis and the involvement of fatty acid synthesis in pimelate production. Cerulenin, an inhibitor of the key fatty acid elongation enzyme, FabF, markedly decreased biotin production by B. subtilis resting cells whereas a strain having a cerulenin-resistant FabF mutant produced more biotin. In addition, supplementation with pimelic acid fully restored biotin production in cerulenin-treated cells. These results indicate that pimelic acid originating from fatty acid synthesis pathway is a bona fide precursor of biotin in B. subtilis. © 2017 John Wiley & Sons Ltd.

Microscopic evaluation of trace metals in cloud droplets in an acid precipitation region.

Science.gov (United States)

Li, Weijun; Wang, Yan; Collett, Jeffrey L; Chen, Jianmin; Zhang, Xiaoye; Wang, Zifa; Wang, Wenxing

2013-05-07

Mass concentrations of soluble trace metals and size, number, and mixing properties of nanometal particles in clouds determine their toxicity to ecosystems. Cloud water was found to be acidic, with a pH of 3.52, at Mt. Lu (elevation 1,165 m) in an acid precipitation region in South China. A combination of Inductively Coupled Plasma Mass Spectrometry (ICPMS) and Transmission Electron Microscopy (TEM) for the first time demonstrates that the soluble metal concentrations and solid metal particle number are surprisingly high in acid clouds at Mt. Lu, where daily concentrations of SO2, NO2, and PM10 are 18 μg m(-3), 7 μg m(-3), and 22 μg m(-3). The soluble metals in cloudwater with the highest concentrations were zinc (Zn, 200 μg L(-1)), iron (Fe, 88 μg L(-1)), and lead (Pb, 77 μg L(-1)). TEM reveals that 76% of cloud residues include metal particles that range from 50 nm to 1 μm diameter with a median diameter of 250 nm. Four major metal-associated particle types are Pb-rich (35%), fly ash (27%), Fe-rich (23%), and Zn-rich (15%). Elemental mapping shows that minor soluble metals are distributed within sulfates of cloud residues. Emissions of fine metal particles from large, nonferrous industries and coal-fired power plants with tall stacks were transported upward to this high elevation. Our results suggest that the abundant trace metals in clouds aggravate the impacts of acid clouds or associated precipitation on the ecosystem and human health.

[Study on Precursors for Synthesis of Anthraquinone Metabolites from Rheum tanguticum].

Science.gov (United States)

Hasi, Qi-mei-ge; Lj, Hai-ling; Cheng, Yan; Menggen, Qi-qi-ge; Zhang, Yang

2015-01-01

To explore the potential precursors of the anthraquinone metabolites from Rheum tanguticum and preliminanly identify the synthesis pathway thereof. Sterile seedlings sprouted from the seeds of Rheum tanguticum were chosen as materials for inducing callus. The effects of different precursors and feeding duration on the callus of Rheum tanguticum and the anthraquinone yield in adult rheum were studied. The greatest improvement of anthraquinone yield was achieved by acetic acid, increasing 43. 9% for the callus and 45. 8% in the adult rheum; the second greatest improvement was achieved by malonic acid, increasing 15. 8% for the callus and only 3. 6% in the adult rheum. The yield of anthraquinone was not influenced significantly by benzoic acid and p-benzoquinone, and in contrast, was inhibited in some degree by shikimic acid and α-ketoglutaric acid. A suitable feeding duration was 36 h, which worked well for the effects of precursors. The precursor for synthesis of anthraquinone metabolites from Rheum tan- guticum is acetic acid, which improves the yields of callus and anthraquinone in adult rheum, concluding that the anthraquinone metabolites are synthesized via polyketone pathway.

Development and Preliminary Assessment of Hemoperfusion Cartridge with Tannic Acid for Toxic Proteins' Precipitation: An In Vitro Model

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Valquíria Miwa Hanai Yoshida

2016-09-01

Full Text Available Charcoal hemoperfusion (CHP is one of the extracorporeal removal techniques that are used to remove toxins from the body. CHP generally is considered the preferred method for extracorporeal extraction of several toxins—toxins that are adsorbed by activated charcoal. Assessments of the tannic acid's protective effects on ophidian poisoning are associated with the toxic proteins' precipitation by tannic acid. The challenge in treating a snakebite lies in removing the injected poison with minimal damage to blood constituent proteins. An alternative is CHP, and this investigation proposed to develop a column for hemoperfuser cartridge, combining charcoal granules trapped between layers of polymeric material conjugated to tannic acid, using an in vitro model scaled to the Wistar rat, which can be tested in an animal model. The cartridge was evaluated using the 22 full factorial design, in duplicate, as a method to study the effects of granulated-charcoal size and tannic acid concentration on the hematologic profile (platelet and leukocyte counts and biochemical profile (total serum protein and albumin dosages of sheep blood. The results demonstrate that charcoal in hemoperfuser cartridge: (1 decreases the serum in sheep blood volume, as consequence, (2 increases the serum proteins' concentration, and (iii exerts slight influence on albumin. The inclusion of tannic acid in hemoperfuser column precipitates some of serum proteins and albumin, decreasing their concentrations in the plasma serum. In conclusion, based on these effects we can suggest the use of 0.02 g tannic acid concentration and 8–20 mesh granulated charcoal in hemoperfuser cartridge for precipitating toxic proteins from snake venoms.

Levels in neurotransmitter precursor amino acids correlate with mental health in patients with breast cancer.

Science.gov (United States)

Hüfner, K; Oberguggenberger, A; Kohl, C; Geisler, S; Gamper, E; Meraner, V; Egeter, J; Hubalek, M; Beer, B; Fuchs, D; Sperner-Unterweger, B

2015-10-01

Breast cancer is the most common cancer among females. Approximately 30% of cancer patients develop depression or depressive adaptation disorder within 5 years post diagnosis. Low grade inflammation and subsequent changes in neurotransmitter levels could be the pathophysiological link. In the current study we investigated the association of neurotransmitter precursor amino acids with a diagnosis of depression or state anxiety in 154 subjects suffering from breast cancer (BCA(+)), depression (DPR(+)), both or neither. Sociodemographic parameters, severity of depressive symptoms, and state anxiety (ANX) were recorded. Neopterin, kynurenine/tryptophan and phenylalanine/tyrosine were analysed by HPLC or ELISA. Significantly higher serum neopterin values were found in DPR(+) patients (p = 0.034) and in ANX(+) subjects (p = 0.008), as a marker of Th1-related inflammation. The phenylalanine/tyrosine ratio (index of the catecholamine pathway) was associated with the factors "breast cancer" and "depression" and their interaction (all p depressive symptoms (r = 0.376, p precursor amino acids correlate with mental health, an effect which was much more pronounced in BCA(+) patients than in BCA(-) subjects. Aside from identifying underlying pathophysiological mechanisms, these results could be the basis for future treatment studies: in BCA(+) patients with depression the use of serotonin-noradrenaline reuptake inhibitors might be recommended while in those with predominant anxiety selective serotonin reuptake inhibitors might be the treatment of choice. Copyright © 2015 Elsevier Ltd. All rights reserved.

Design of Test Facility to Evaluate Boric Acid Precipitation Following a LOCA

Energy Technology Data Exchange (ETDEWEB)

Suh, Jeong-Kwan; Song, Yong-Jae [KHNP CRI, Daejeon (Korea, Republic of)

2016-10-15

The U.S.NRC has identified a concern that debris associated with generic safety issue (GSI) - 191 may affect the potential precipitation of boric acid due to one or more of the following phenomena: - Reducing mass transport (i.e. mixing) between the core and the lower plenum (should debris accumulate at the core inlet) - Reduced lower plenum volume (should debris settle in the lower plenum), and, - Increased potential for boric acid precipitation (BAP) in the core (should debris accumulate in suspension in the core) To address these BAP issues, KHNP is planning to conduct validation tests by constructing a BAP test facility. This paper describes the design of test facility to evaluate BAP following a LOCA. The design of BAP test facility has been developed by KHNP. To design the test facility, test requirements and success criteria were established, and scaling analysis of power-to-volume method, Ishii-Kataoka method, and hierarchical two-tiered method were investigated. The test section is composed of two fuel assemblies with half of full of prototypic FA height. All the fuel rods are heated by the electric power supplier. The BAP tests in the presence of debris, buffering agents, and boron will be performed following the test matrix.

Biogenic precipitation of manganese oxides and enrichment of heavy metals at acidic soil pH

Science.gov (United States)

Mayanna, Sathish; Peacock, Caroline L.; Schäffner, Franziska; Grawunder, Anja; Merten, Dirk; Kothe, Erika; Büchel, Georg

2014-05-01

The precipitation of biogenic Mn oxides at acidic pH is rarely reported and poorly understood, compared to biogenic Mn oxide precipitation at near neutral conditions. Here we identified and investigated the precipitation of biogenic Mn oxides in acidic soil, and studied their role in the retention of heavy metals, at the former uranium mining site of Ronneburg, Germany. The site is characterized by acidic pH, low carbon content and high heavy metal loads including rare earth elements. Specifically, the Mn oxides were present in layers identified by detailed soil profiling and within these layers pH varied from 4.7 to 5.1, Eh varied from 640 to 660 mV and there were enriched total metal contents for Ba, Ni, Co, Cd and Zn in addition to high Mn levels. Using electron microprobe analysis, synchrotron X-ray diffraction and X-ray absorption spectroscopy, we identified poorly crystalline birnessite (δ-MnO2) as the dominant Mn oxide in the Mn layers, present as coatings covering and cementing quartz grains. With geochemical modelling we found that the environmental conditions at the site were not favourable for chemical oxidation of Mn(II), and thus we performed 16S rDNA sequencing to isolate the bacterial strains present in the Mn layers. Bacterial phyla present in the Mn layers belonged to Firmicutes, Actinobacteria and Proteobacteria, and from these phyla we isolated six strains of Mn(II) oxidizing bacteria and confirmed their ability to oxidise Mn(II) in the laboratory. The biogenic Mn oxide layers act as a sink for metals and the bioavailability of these metals was much lower in the Mn layers than in adjacent layers, reflecting their preferential sorption to the biogenic Mn oxide. In this presentation we will report our findings, concluding that the formation of natural biogenic poorly crystalline birnessite can occur at acidic pH, resulting in the formation of a biogeochemical barrier which, in turn, can control the mobility and bioavailability of heavy metals in

Facile synthesis and enhanced visible light photocatalytic activity of N and Zr co-doped TiO2 nanostructures from nanotubular titanic acid precursors

Science.gov (United States)

Zhang, Min; Yu, Xinluan; Lu, Dandan; Yang, Jianjun

2013-12-01

Zr/N co-doped TiO2 nanostructures were successfully synthesized using nanotubular titanic acid (NTA) as precursors by a facile wet chemical route and subsequent calcination. These Zr/N-doped TiO2 nanostructures made by NTA precursors show significantly enhanced visible light absorption and much higher photocatalytic performance than the Zr/N-doped P25 TiO2 nanoparticles. Impacts of Zr/N co-doping on the morphologies, optical properties, and photocatalytic activities of the NTA precursor-based TiO2 were thoroughly investigated. The origin of the enhanced visible light photocatalytic activity is discussed in detail.

Synthesis of highly sinterable YAG nanopowders by a modified co-precipitation method

International Nuclear Information System (INIS)

Chen, Zhi-Hui; Yang, Yun; Hu, Zhang-Gui; Li, Jiang-Tao; He, Shu-Li

2007-01-01

A hydrate precursor of yttrium aluminum garnet (YAG) was synthesized by a modified co-precipitation method, in which n-butanol was employed as a low-cost recyclable dehydration solvent. A mixed solution of ethanol and ammonia were used as precipitant. Pure YAG phase appeared after the as-prepared precursors being calcined at 850 o C for 2 h. The nanocrystalline YAG particles calcined at 1100 o C were well dispersed with average diameter of about 40 nm, which can be densified to transparency under vacuum sintering at 1700 o C for 5 h with TEOS as sintering additive

Thermal behavior and phase transformation of ZrO{sub 2}–10%SiO{sub 2} precursor powder prepared by a co-precipitation route without adding stability agent

Energy Technology Data Exchange (ETDEWEB)

Chu, Hsueh-Liang [Department of Materials Science and Engineering, National Cheng Kung University, 1 Ta-Hsueh Road, Tainan 70101, Taiwan (China); Hwang, Weng-Sing [Department of Materials Science and Engineering, National Cheng Kung University, 1 Ta-Hsueh Road, Tainan 70101, Taiwan (China); Institute of Nanotechnology and Microsystems Engineering, National Cheng Kung University, 1 Ta-Hsueh Road, Tainan 70101, Taiwan (China); Wang, Cheng-Li [Department of Materials Science and Engineering, National Cheng Kung University, 1 Ta-Hsueh Road, Tainan 70101, Taiwan (China); Wang, Moo-Chin, E-mail: mcwang@kmu.edu.tw [Department of Fragrance and Cosmetic Science, Kaohsiung Medical University, 100 Shih-Chuan 1st Road, Kaohsiung 80708, Taiwan (China); Lee, Kuen-Chan [Department of Fragrance and Cosmetic Science, Kaohsiung Medical University, 100 Shih-Chuan 1st Road, Kaohsiung 80708, Taiwan (China); Huang, Hong-Hsin [Department of Electrical Engineering, Cheng Shiu University, 840 Cheng Ching Road, Niaosong, Kaohsiung 83347, Taiwan (China); Lee, Huey-Er, E-mail: huerle@kmu.edu.tw [School of Dentistry, College of Dental Medicine, Kaohsiung Medical University, 100 Shih-Chuan 1st Road, Kaohsiung 807, Taiwan (China); Department of Dentistry, Kaohsiung Medical University, 100 Tzyou 1st Road, Kaohsiung 807, Taiwan (China)

2014-12-15

Highlights: • The precursor powders contained about 68.3 wt% ZrO{sub 2}, which corresponds to ZrO{sub 2}·1/8 H{sub 2}O. • The exothermic peak temperature of tetragonal ZrO{sub 2} formation occurred at 1014 K. • The activation energy of ZrO{sub 2}–10%SiO{sub 2} precursors crystallization is 993.7 kJ/mol. • Only the tetragonal ZrO{sub 2} formed when the precursor calcined at 1173–1373 K for 2 h. • As calcined at 1473 K for 2 h, tetragonal ZrO{sub 2} fully converted to monoclinic ZrO{sub 2}. - Abstract: Thermal behavior and phase transformation of ZrO{sub 2}–10%SiO{sub 2} precursor powder prepared by a co-precipitation route without adding stability agent has been studied using different thermal analysis/thermogravimetry (DTA/TG), X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), nano beam electron diffraction (NBED), high-resolution TEM (HRTEM) and energy-dispersive X-ray spectrometer (EDS). The TG results show that four weight loss regions were from 298 to 443 K, 443 to 743 K, 743 to 793 K and 793 to 1400 K. The DTA result shows that the ZrO{sub 2} freeze-dried precursor powders crystallization at 1014 K. The activation energy of 993.7 kJ/mol was obtained for tetragonal ZrO{sub 2} crystallization using a non-isothermal process. The XRD result shows that only a single phase of tetragonal ZrO{sub 2} appears when the freeze-dried precursor powders after calcination between 1173 and 1373 K for 2 h. Moreover, when calcined at 1473 K for 2 h, the phase transformation from tetragonal ZrO{sub 2} fully converted to monoclinic ZrO{sub 2} occurred.

Facile synthesis of a conjugation-grafted-TiO2 nanohybrid with enhanced visible-light photocatalytic properties from nanotube titanic acid precursors

Science.gov (United States)

Guo, Yanru; Zhang, Min; Zhang, Zhihua; Li, Qiuye; Yang, Jianjun

2016-08-01

A conjugation-grafted-TiO2 nanohybrid was synthesized by chemically grafting conjugated structures on the surface of nanotube titanic acid (NTA) precursor-based TiO2 through the controlled thermal degradation of a coacervated polymer layer of polyvinyl alcohol (PVA). The interfacial interactions between the NTA precursor-based TiO2 and conjugated structures were characterized using Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Moreover, the effects of the NTA's pretreatment temperature and the weight ratio of NTA to PVA on the photocatalytic degradation of methyl orange were also investigated. A higher NTA pretreatment temperature and a lower NTA to PVA weight ratio were found to enhance photogenerated electron-hole separation efficiency and photocatalytic activity. Moreover, the conjugation-grafted-TiO2 nanohybrid synthesized from the NTA precursor displayed a much higher visible-light photocatalytic activity than that of the sample obtained from the P25 precursor. The origin of the enhanced photocatalytic activity under visible-light irradiation is also discussed in detail.

CONCENTRATION OF Pu USING AN IODATE PRECIPITATE

Science.gov (United States)

Fries, B.A.

1960-02-23

A method is given for separating plutonium from lanthanum in a lanthanum fluoride carrier precipitation process for the recovery of plutonium values from an aqueous solution. The carrier precipitation process includes the steps of forming a lanthanum fluoride precipi- . tate, thereby carrying plutonium out of solution, metathesizing the fluoride precipitate to a hydroxide precipitate, and then dissolving the hydroxide precipitate in nitric acid. In accordance with the invention, the nitric acid solution, which contains plutonium and lanthanum, is made 0.05 to 0.15 molar in potassium iodate. thereby precipitating plutonium as plutonous iodate and the plutonous iodate is separated from the lanthanum- containing supernatant solution.

Economic valuation of acidic deposition damages: Preliminary results from the 1985 NAPAP [National Acid Precipitation Assessment Program] damage assessment

International Nuclear Information System (INIS)

Callaway, J.M.; Darwin, R.F.; Nesse, R.J.

1985-01-01

This paper identifies methods used to evaluate the economic damages of acid deposition in the 1985 Damage Assessment being coordinated by the National Acid Precipitation Program. It also presents the preliminary estimates of economic damages for the Assessment. Economic damages are estimated for four effect areas: commercial agriculture and forests, recreational fishing and selected types of materials. In all but the last area, methods are used which incorporate the behavioral responses of individuals and firms or simulated physical damages to resources at risk. The preliminary nature of the estimated damages in each area is emphasized. Over all, the damage estimates should be interpreted with caution. 44 refs., 6 figs., 5 tabs

Selenopentathionic and Telluropentathionic Acids as Precursors for Formation of Semiconducting Layers on the Surface of Polyamide

Directory of Open Access Journals (Sweden)

Skirma Zalenkiene

2007-01-01

Full Text Available The layers of copper chalcogenides, which were formed on the surface of semihydrophilic polymer—polyamide 6 (PA using monoselenopentathionic H2SeS4O6 and monotelluropentathionic H2TeS4O6 acids as precursors of chalcogens, were characterized. Fourier transform infrared (FT-IR and UV spectroscopy were used to monitor the effect of chalcogens on the changes in structure of PA corresponding to the concentration of the precursor's solution and an exposure time. The IR spectra of modified PA were completely different from that of the initial PA. Further interaction of chalcogenized PA with copper (II/I salt solution leads to the formation of CuxS, CuxSe, CuxTe, and mixed –CuxS–CuySe and CuxS–CuyTe layers which have different electric transport properties. The surface properties of PA after treatment are studied using AFM and XRD. The electrical resistances of layers with various composition formed over a wide concentration range 0.01–0.5 mol⋅dm−3 of precursor's solution were measured. Variation in the conductivity of layers of Cu–Se–S and Cu–Te–S on the surface of PA shows an evident increase with the increasing of the mass fraction of selenium or tellurium.

Continuous precipitation process of plutonium salts; Procede continu de precipitation des sels de plutonium

Energy Technology Data Exchange (ETDEWEB)

Richard, P [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

1967-03-01

This work concerns the continuous precipitation process of plutonium oxalate. Investigations about the solubility of different valence states in nitric-oxalic and in nitric-sulfuric-oxalic medium lead to select the precipitation process of tetravalent plutonium oxalate. Settling velocity and granulometry of tetravalent oxalate plutonium have been studied with variation of several precipitation parameters such as: temperature, acidity, excess of oxalic acid and aging time. Then are given test results of some laboratory continuous apparatus. Conditions of operation with adopted tubular apparatus are defined in conclusion. A flow-sheet is given for a process at industrial scale. (author) [French] Cette etude porte sur la precipitation continue de l'oxalate de plutonium. L'etude de la solubilite des differentes valences du plutonium dans des milieux acides nitrique-oxalique, puis nitrique-sulfurique-oxalique conduit a choisir la precipitation de l'oxalate de plutonium tetravalent. L'etude porte ensuite sur la sedimentation et la granulometrie de l'oxalate de Pu{sup 4+} obtenue en faisant varier differents parametres de la precipitation : la temperature, l'acidite, l'exces oxalique et le temps de murissement. La derniere partie traite des resultats obtenus avec plusieurs types d'appareils continus essayes au laboratoire. En conclusion sont donnees les conditions de marche de l'appareil tubulaire adopte, ainsi qu'une extrapolation a l'echelle industrielle sous forme d'un flow-sheet. (auteur)

Recovery of Vanadium from H2SO4-HF Acidic Leaching Solution of Black Shale by Solvent Extraction and Precipitation

Directory of Open Access Journals (Sweden)

Xingbin Li

2016-03-01

Full Text Available The recovery of vanadium from sulfuric and hydrofluoric mixed acid solutions generated by the direct leaching of black shale was investigated using solvent extraction and precipitation methods. The process consisted of reduction, solvent extraction, and stripping, followed by precipitation and calcination to yield vanadium pentoxide. The influence of various operating parameters on the extraction and recovery of vanadium was studied. Vanadium (IV was selectively extracted using a mixture of 10% (v/v di(2-ethylhexylphosphoric acid and 5% (v/v tri-n-butylphosphate in sulfonated kerosene. Using six extraction and five stripping stages, the extraction efficiency for vanadium was 96.7% and the stripping efficiency was 99.7%. V2O5 with a purity of 99.52% was obtained by oxidation of the loaded strip solution and precipitation of ammonium polyvanadate at pH 1.8 to 2.2, followed by calcination of the dried precipitate at 550 °C for 2 h. It was concluded that the combination of solvent extraction and precipitation is an efficient method for the recovery of vanadium from a multi-element leach solution generated from black shale.

Synthesis and purification of oxide nanoparticle dispersions by modified emulsion precipitation.

Science.gov (United States)

Shi, Jingyu; Verweij, Henk

2005-06-07

ZrO2 and Fe2O3 precursor nanoparticles are synthesized, well-dispersed in decane, via a modified emulsion precipitation (MEP) method. This method starts with preparing two thermostable water-in-oil (w/o) emulsions with nonylphenol tetra(ethylene glycol) ether (Arkopal-40) as the main surfactant, didodecyldimethylammonium bromide (DiDAB) as the cosurfactant, decane as the continuous oil phase, and either a metal salt solution or a hexamethylenetetramine (HMTA) precipitation agent solution as the dispersed water phase. After mixing of the two emulsions, individual precursor particles are formed by precipitation in the confinement of the aqueous solution droplets. Excess water is removed by azeotropic distillation, and steric stabilization of the particles in the remaining oil medium is achieved with poly(octadecyl methacrylate) (PODMA), initially present dissolved in the oil phase. A purification process is conducted to remove the precipitation reaction byproduct and excess surfactants from the nanoparticle dispersions. Transmission electron microscopy (TEM) characterization shows that the ZrO2 and Fe2O3 precursor nanoparticles are both non-agglomerated, spherical, and have a narrow particle size distribution, centered at 4 nm in diameter. The precipitation from the dispersion of byproduct NH4Cl after water removal, and insoluble surfactant DiDAB after dilution with pure decane, is confirmed by X-ray diffraction (XRD). NMR results show that most of the oil-soluble surfactant Arkopal-40 can be removed from the dispersion by a 3x repeated dead-end pressure filtration process. It is shown that, after purification, the nanoparticle dispersions can be used for the preparation of homogeneous nanostructured coatings. The purification procedure as discussed provides guidelines for up-scaling the process and reuse of emulsifiers.

STRONTIUM PRECIPITATION

Science.gov (United States)

McKenzie, T.R.

1960-09-13

A process is given for improving the precipitation of strontium from an aqueous phosphoric-acid-containing solution with nickel or cobalt ferrocyanide by simultaneously precipitating strontium or calcium phosphate. This is accomplished by adding to the ferrocyanide-containing solution calcium or strontium nitrate in a quantity to yield a concentration of from 0.004 to 0.03 and adjusting the pH of the solution to a value of above 8.

Incorporation and distribution of dihomo-gamma-linolenic acid, arachidonic acid, and eicosapentaenoic acid in cultured human keratinocytes

International Nuclear Information System (INIS)

Punnonen, K.; Puustinen, T.; Jansen, C.T.

1986-01-01

Human keratinocytes in culture were labelled with 14 C-dihomo-gamma-linolenic acid, 14 C-arachidonic acid or 14 C-eicosapentaenoic acid. All three eicosanoid precursor fatty acids were effectively incorporated into the cells. In phospholipids most of the radioactivity was recovered, in neutral lipids a substantial amount, and as free unesterified fatty acids only a minor amount. Most of the radioactivity was found in phosphatidylethanolamine which was also the major phospholipid as measured by phosphorous assay. The incorporation of dihomo-gamma-linolenic acid and arachidonic acid into lipid subfractions was essentially similar. Eicosapentaenoic acid was, however, much less effectively incorporated into phosphatidylinositol + phosphatidylserine and, correspondingly, more effectively into triacylglycerols as compared to the two other precursor fatty acids. Once incorporated, the distribution of all three precursor fatty acids was relatively stable, and only minor amounts of fatty acids were released into the culture medium during short term culture (two days). Our study demonstrates that eicosanoid precursor fatty acids are avidly taken up by human keratinocytes and esterified into membrane lipids. The clinical implication of this finding is that dietary manipulations might be employed to cause changes in the fatty acid composition of keratinocytes

Precipitation of humic acid with divalent ions

DEFF Research Database (Denmark)

Andersen, Niels Peder Raj; Mikkelsen, Lene Haugaard; Keiding, Kristian

2001-01-01

and Ba2+. The phase diagram model can not account for the observed precipitation in region III and However, in region IV the HA appears to posses colloidal properties, which is supported by precipitation taking place at a constant zeta-potential -21mV with the same amount of added barium ion regardless...

Acid Rain Examination and Chemical Composition of Atmospheric Precipitation in Tehran, Iran

Directory of Open Access Journals (Sweden)

Mohsen Saeedi

2012-01-01

Full Text Available Air pollution is one of the most important environmental problems in metropolitan cities like Tehran. Rain and snow, as natural events, may dissolve and absorb contaminants of the air and direct them onto the land or surface waters which become polluted. In the present study, precipitation samples were collected from an urbanized area of Tehran. They were analyzed for NO3-, PO43-, SO42-, pH, turbidity, Electrical Conductivity (EC, Cu, Fe, Zn, Pb, Ni, Cr, and Al. We demonstrate that snow samples were often more polluted and had lower pH than those from the rain, possibly as an effect of adsorption capability of snow flakes. Volume weighted average concentrations were calculated and compared with some other studies. Results revealed that Tehran's precipitations are much more polluted than those reported from other metropolitan cities. Cluster analysis revealed that studied parameters such as metals and acidity originated from the same sources, such as fuel combustion in residential and transportation sectors of Tehran.

TCA precipitation.

Science.gov (United States)

Koontz, Laura

2014-01-01

Trichloroacetic acid (TCA) precipitation of proteins is commonly used to concentrate protein samples or remove contaminants, including salts and detergents, prior to downstream applications such as SDS-PAGE or 2D-gels. TCA precipitation denatures the protein, so it should not be used if the protein must remain in its folded state (e.g., if you want to measure a biochemical activity of the protein). © 2014 Elsevier Inc. All rights reserved.

Inhibition of calcium phosphate precipitation under environmentally-relevant conditions

International Nuclear Information System (INIS)

Cao Xinde; Harris, Willie G.; Josan, Manohardeep S.; Nair, Vimala D.

2007-01-01

Precipitation of Ca phosphates plays an important role in controlling P activity and availability in environmental systems. The purpose of this study was to determine inhibitory effects on Ca phosphate precipitation by Mg 2+ , SO 4 2- , CO 3 2- , humic acid, oxalic acid, biogenic Si, and Si-rich soil clay commonly found in soils, sediments, and waste streams. Precipitation rates were determined by measuring decrease of P concentration in solutions during the first 60 min; and precipitated solid phases identified using X-ray diffraction and electron microscopy. Poorly-crystalline hydroxyapatite (HAP: Ca 5 (PO 4 ) 3 OH) formed in control solutions over the experiment period of 24 h, following a second-order dependence on P concentration. Humic acid and Mg 2+ significantly inhibited formation of HAP, allowing formation of a more soluble amorphous Ca phosphate phase (ACP), and thus reducing the precipitation rate constants by 94-96%. Inhibition caused by Mg 2+ results from its incorporation into Ca phosphate precipitates, preventing formation of a well-crystalline phase. Humic acid likely suppressed Ca phosphate precipitation by adsorbing onto the newly-formed nuclei. Presence of oxalic acid resulted in almost complete inhibition of HAP precipitation due to preemptive Ca-oxalate formation. Carbonate substituted for phosphate, decreasing the crystallinity of HAP and thus reducing precipitation rate constant by 44%. Sulfate and Si-rich solids had less impact on formation of HAP; while they reduced precipitation in the early stage, they did not differ from the control after 24 h. Results indicate that components (e.g., Mg 2+ , humic acid) producing relatively soluble ACP are more likely to reduce P stability and precipitation rate of Ca phosphate in soils and sediments than are components (e.g., SO 4 2- , Si) that have less effect on the crystallinity

Process for producing ceramic nitrides anc carbonitrides and their precursors

Science.gov (United States)

Brown, G.M.; Maya, L.

1987-02-25

A process for preparing ceramic nitrides and carbon nitrides in the form of very pure, fine particulate powder. Appropriate precursors is prepared by reaching a transition metal alkylamide with ammonia to produce a mixture of metal amide and metal imide in the form of an easily pyrolyzable precipitate.

Photoluminescent properties of Y2O3:Eu3+ phosphors prepared via urea precipitation in non-aqueous solution

International Nuclear Information System (INIS)

Sun, Y.; Qi, L.; Lee, M.; Lee, B.I.; Samuels, W.D.; Exarhos, G.J.

2004-01-01

Europium-doped yttrium oxide phosphors were obtained by firing precursors prepared by urea precipitation in ethanol and ethylenediamine. The precipitation in non-aqueous solution was carried out in an autoclave at 150 deg. C to allow the decomposition of urea. The photoluminescent intensities of the phosphors prepared in ethanol and ethylenediamine increased by about 30% compared to that of the phosphor prepared by the conventional urea homogeneous precipitation in aqueous solution. Amorphous carbonates and amorphous hydroxides/carbonates mixtures were identified as precursors from ethanol and ethylenediamine, respectively. The morphology and particle size were studied by SEM and dynamic laser scattering method

Modeling of liquid ceramic precursor droplets in a high velocity oxy-fuel flame jet

International Nuclear Information System (INIS)

Basu, Saptarshi; Cetegen, Baki M.

2008-01-01

Production of coatings by high velocity oxy-fuel (HVOF) flame jet processing of liquid precursor droplets can be an attractive alternative method to plasma processing. This article concerns modeling of the thermophysical processes in liquid ceramic precursor droplets injected into an HVOF flame jet. The model consists of several sub-models that include aerodynamic droplet break-up, heat and mass transfer within individual droplets exposed to the HVOF environment and precipitation of ceramic precursors. A parametric study is presented for the initial droplet size, concentration of the dissolved salts and the external temperature and velocity field of the HVOF jet to explore processing conditions and injection parameters that lead to different precipitate morphologies. It is found that the high velocity of the jet induces shear break-up into several μm diameter droplets. This leads to better entrainment and rapid heat-up in the HVOF jet. Upon processing, small droplets (<5 μm) are predicted to undergo volumetric precipitation and form solid particles prior to impact at the deposit location. Droplets larger than 5 μm are predicted to form hollow or precursor containing shells similar to those processed in a DC arc plasma. However, it is found that the lower temperature of the HVOF jet compared to plasma results in slower vaporization and solute mass diffusion time inside the droplet, leading to comparatively thicker shells. These shell-type morphologies may further experience internal pressurization, resulting in possibly shattering and secondary atomization of the trapped liquid. The consequences of these different particle states on the coating microstructure are also discussed in this article

Detrital processing in streams exposed to acidic precipitation in the Central Appalachian Mountains

International Nuclear Information System (INIS)

Meegan, S.K.; Perry, S.A.; Perry, W.B.

1996-01-01

Continuing high rates of acidic deposition in the eastern United States may lead to long-term effects on stream communities, because sensitive catchments are continuing to lose anions and cations. A two-year study of the effects of pH and associated water chemistry variables on detrital processing in three streams with different bedrock geology in the Monongahela National Forest, West Virginia were investigated. Leaf pack processing rates and macroinvertebrate colonization and microbial biomass (ATP concentration) on the packs in the three stream were compared. It was found that macroinvertebrate and microbial communities differed both among streams that differed in their capacity to buffer the effects of acidic precipitation and among years in the same stream; these differences in biotic communities were not large enough to affect rates of leaf processing between the two years of the study, but they did significantly affect processing rates between acidic and circumneutral streams

Gas Antisolvent Approach for the Precipitation of α -Methoxyphenylacetic Acid – ( R -1-Cyclohexylethylamine Diateromeric Salt

Directory of Open Access Journals (Sweden)

A. Zodge

2017-10-01

Full Text Available One of the major drawbacks of diastereomeric salt precipitation based enantioseparation is the time and solvent requirement of crystallization. In the gas antisolvent (GAS approach, supercritical carbon dioxide is applied as an antisolvent, and the precipitation takes place in a couple of minutes. By setting the process parameters diastereomeric excess, yields, and selectivity can be controlled. Applicability of the process is demonstrated on the resolution of racemic 2-methoxyphenylacetic acid with enantiopure (R-(−-1-cyclohexylethylamine. Diastereomeric excess values over 55 % along with 80 % yields were achieved at optimal conditions in a single step.

PRECIPITATION OF PROTACTINIUM

Science.gov (United States)

Moore, R.L.

1958-07-15

An lmprovement in the separation of protactinium from aqueous nitric acid solutions is described. 1t covers the use of lead dioxide and tin dioxide as carrier precipitates for the protactinium. In carrying out the process, divalent lead or divalent tin is addcd to the solution and oxidized, causing formation of a carrier precipitate of lead dioxide or stannic oxide, respectively.

Biochemical precursor effects on the fatty acid production in cell suspension cultures of Theobroma cacao L.

Science.gov (United States)

Parra, O; Gallego, A M; Urrea, A; Rojas, L F; Correa, C; Atehortúa, L

2017-02-01

Cocoa butter (CB) is composed of 96% palmitic, stearic, oleic, linoleic and linolenic fatty acids that are responsible for the hardness, texture and fusion properties of chocolate. Through in vitro plant cell culture it is possible to modify CB lipid profiles and to study the fatty acid biosynthesis pathway on a subcellular level, evaluating fundamental aspects to enhance in vitro fatty acid production in a specific and controlled way. In this research, culture media was supplemented with acetate, biotin, pyruvate, bicarbonate and glycerol at three different concentrations and the effects on the biomass production (g/L), cell viability, and fatty acids profile and production was evaluated in in vitro cell suspensions culture. It was found that biotin stimulated fatty acid synthesis without altering cell viability and cell growth. It was also evident a change in the lipid profile of cell suspensions, increasing middle and long chain fatty acids proportion, which are unusual to those reported in seeds; thus implying that it is possible to modify lipid profiles according to the treatment used. According to the results of sucrose gradients and enzyme assays performed, it is proposed that cacao cells probably use the pentose phosphate pathway, mitochondria being the key organelle in the carbon flux for the synthesis of reductant power and fatty acid precursors. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

Stable amorphous georgeite as a precursor to a high-activity catalyst

DEFF Research Database (Denmark)

Kondrat, Simon A.; Smith, Paul J.; Wells, Peter P.

2016-01-01

Copper and zinc form an important group of hydroxycarbonate minerals that include zincian malachite, aurichalcite, rosasite and the exceptionally rare and unstable-and hence little known and largely ignored-georgeite. The first three of these minerals are widely used as catalyst precursors...... for the industrially important methanol-synthesis and low-temperature water-gas shift (LTS) reactions, with the choice of precursor phase strongly influencing the activity of the final catalyst. The preferred phase is usually zincian malachite. This is prepared by a co-precipitation method that involves the transient...

Magnetic Properties of Ni-Zn Ferrite Prepared with the Layered Precursor Method

International Nuclear Information System (INIS)

Zhou Xin; Hou Zhi-Ling; Li Feng; Qi Xin

2010-01-01

We prepare NiZnFe 2 O 4 soft magnetic ferrites with different molar ratios with the layered precursor method and investigate their magnetic properties. In the layered precursor, metal ions are scattered on the layer plate in a certain way on account of the effect of lowest lattice energy and lattice orientation. After high temperature calcinations, spinel ferrites with uniform structural component and single magnetic domain can be obtained, and the magnetic property is improved greatly. NiZnFe 2 O 4 ferrites prepared have the best specific saturation magnetization of 79.15 emu·g −1 , higher than that of 68 emu·g −1 prepared by the chemical co-precipitation method and that of 59 emu·g −1 prepared by the emulsion-gel method. Meanwhile the coercivity of NiZnFe 2 O 4 ferrites prepared by layered precursor method is 14 kA·m −1 , lower than that of 50 emu·g −1 prepared by the co-precipitation method and that of 59 emu·g −1 prepared by the emulsion-gel method. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

IMPROVED PROCESS OF PLUTONIUM CARRIER PRECIPITATION

Science.gov (United States)

Faris, B.F.

1959-06-30

This patent relates to an improvement in the bismuth phosphate process for separating and recovering plutonium from neutron irradiated uranium, resulting in improved decontamination even without the use of scavenging precipitates in the by-product precipitation step and subsequently more complete recovery of the plutonium in the product precipitation step. This improvement is achieved by addition of fluomolybdic acid, or a water soluble fluomolybdate, such as the ammonium, sodium, or potassium salt thereof, to the aqueous nitric acid solution containing tetravalent plutonium ions and contaminating fission products, so as to establish a fluomolybdate ion concentration of about 0.05 M. The solution is then treated to form the bismuth phosphate plutonium carrying precipitate.

National Acid Precipitation Assessment Program Report to Congress: An Integrated Assessment

Energy Technology Data Exchange (ETDEWEB)

Uhart, M.; et al,

2005-08-01

Under Title IX of the 1990 Clean Air Act Amendments, Congress reauthorized the National Acid Precipitation Assessment Program (NAPAP) to continue coordinating acid rain research and monitoring, as it had done during the previous decade, and to provide Congress with periodic reports. In particular, Congress asked NAPAP to assess all available data and information to answer two questions: (1) What are the costs, benefits, and effectiveness of Title IV? This question addresses the costs and economic impacts of complying with the Acid Rain Program as well as benefit analyses associated with the various human health and welfare effects, including reduced visibility, damages to materials and cultural resources, and effects on ecosystems. (2) What reductions in deposition rates are needed to prevent adverse ecological effects? This complex questions addresses ecological systems and the deposition levels at which they experience harmful effects. The results of the assessment of the effects of Title IV and of the relationship between acid deposition rates and ecological effects were to be reported to Congress quadrennially, beginning with the 1996 report to Congress. The objective of this Report is to address the two main questions posed by Congress and fully communicate the results of the assessment to decision-makers. Given the primary audience, most of this report is not written as a technical document, although information supporting the conclusions is provided along with references.

Ultrasound assisted co-precipitation of nanostructured CuO-ZnO-Al2O3 over HZSM-5: effect of precursor and irradiation power on nanocatalyst properties and catalytic performance for direct syngas to DME.

Science.gov (United States)

Allahyari, Somaiyeh; Haghighi, Mohammad; Ebadi, Amanollah; Hosseinzadeh, Shahin

2014-03-01

Nanostructured CuO-ZnO-Al2O3/HZSM-5 was synthesized from nitrate and acetate precursors using ultrasound assisted co-precipitation method under different irradiation powers. The CuO-ZnO-Al2O3/HZSM-5 nanocatalysts were characterized using XRD, FESEM, BET, FTIR and EDX Dot-mapping analyses. The results indicated precursor type and irradiation power have significant influences on phase structure, morphology, surface area and functional groups. It was observed that the acetate formulated CuO-ZnO-Al2O3/HZSM-5 nanocatalyst have smaller CuO crystals with better dispersion and stronger interaction between components in comparison to nitrate based nanocatalysts. Ultrasound assisted co-precipitation synthesis method resulted in nanocatalyst with more uniform morphology compared to conventional method and increasing irradiation power yields smaller particles with better dispersion and higher surface area. Additionally the crystallinity of CuO is lower at high irradiation powers leading to stronger interaction between metal oxides. The nanocatalysts performance were tested at 200-300 °C, 10-40 bar and space velocity of 18,000-36,000 cm(3)/g h with the inlet gas composition of H2/CO = 2/1 in a stainless steel autoclave reactor. The acetate based nanocatalysts irradiated with higher levels of power exhibited better reactivity in terms of CO conversion and DME yield. While there is an optimal temperature for CO conversion and DME yield in direct synthesis of DME, CO conversion and DME yield both increase with the pressure increase. Furthermore ultrasound assisted co-precipitation method yields more stable CuO-ZnO-Al2O3/HZSM-5 nanocatalyst while conventional precipitated nanocatalyst lost their activity ca. 18% and 58% in terms of CO conversion and DME yield respectively in 24 h time on stream test.

Amino Acid Precursor Supply in the Biosynthesis of the RNA Polymerase Inhibitor Streptolydigin by Streptomyces lydicus▿†

OpenAIRE

Gómez, Cristina; Horna, Dina H.; Olano, Carlos; Palomino-Schätzlein, Martina; Pineda-Lucena, Antonio; Carbajo, Rodrigo J.; Braña, Alfredo F.; Méndez, Carmen; Salas, José A.

2011-01-01

Biosynthesis of the hybrid polyketide-nonribosomal peptide antibiotic streptolydigin, 3-methylaspartate, is utilized as precursor of the tetramic acid moiety. The three genes from the Streptomyces lydicus streptolydigin gene cluster slgE1-slgE2-slgE3 are involved in 3-methylaspartate supply. SlgE3, a ferredoxin-dependent glutamate synthase, is responsible for the biosynthesis of glutamate from glutamine and 2-oxoglutarate. In addition to slgE3, housekeeping NADPH- and ferredoxin-dependent glu...

Parametric study on co-precipitation of U/Th in MOX fuel of AHWR

International Nuclear Information System (INIS)

Tiwari, S.K.; Swaroopa Lakshmi, Y.; Nath, Baidurjya; Setty, D.S.; Kalyana Krishnan, G.; Saibaba, N.

2015-01-01

During manufacturing of Mixed Oxide Fuel (MOX) pellets for Advance Heavy Water Reactor (AHWR-LEU), around 30% rejected MOX pellets are generated in every cycle. These rejected MOX pellets are dissolved in nitric acid for recovery of U/Th. The recovered U/Th is recycled for production of MOX pellets. MOX pellets of varying compositions are used in AHWR fuel. Dissolution of MOX pellets in nitric acid is a challenging task because of its low surface area and longer dissolution times. High normal nitric acid is used in order to increase rate of dissolution, which in turn results in generation of high free acidity solution which influences the precipitation characteristics of Uranium (VI) by oxalic acid. Oxalic acid precipitation helps in generation of nitric acid which can be used for dissolution there by effectively facilitating nil effluent generation. Precipitation by oxalic acid unlike ammonia has advantage of zero liquid effluent discharge by complete recycle of oxalate filtrate to dissolution section. In the present work, the effect of various parameters like free acidity, residence time, concentration of oxalic acid, initial concentration of uranium and thorium etc. on the precipitation of U(VI) and Th(IV) in nitrate media by oxalic acid was carried out. The precipitated powder was subjected to various morphological evaluations like particle size etc. Study of various parameters on the co-precipitation of uranium and thorium by oxalic acid was carried out. It was observed that complete precipitation (> 99.9%) of thorium as oxalate does not depend on free acidity range (1- 6 N). Excess oxalic acid is not required for complete precipitation of thorium oxalate. The precipitation of uranyl oxalate varies with initial free acidity of solution. Uranyl oxalate precipitation does not take place at and above 5 N of free acidity

Fractionation of equine antivenom using caprylic acid precipitation in combination with cationic ion-exchange chromatography.

Science.gov (United States)

Raweerith, Rutai; Ratanabanangkoon, Kavi

2003-11-01

A combined process of caprylic acid (CA) precipitation and ion-exchange chromatography on SP-Sepharose was studied as a means to fractionate pepsin-digested horse antivenom F(ab')(2) antibody. In the CA precipitation, the optimal concentration for fractionation of F(ab')(2) from pepsin-digested horse plasma was 2%, in which 89.61% of F(ab')(2) antibody activity was recovered in the supernatant with 1.5-fold purification. A significant amount of pepsin was not precipitated and remained active under these conditions. An analytical cation exchanger Protein-Pak SP 8HR HPLC column was tested to establish optimal conditions for the effective separation of IgG, albumin, pepsin and CA from the F(ab')(2) product. From these results, the supernatant from CA precipitation of pepsin-digested plasma was subjected to a SP-Sepharose column chromatography using a linear salt gradient. With stepwise elution, a peak containing F(ab')(2) antibody could be obtained by elution with 0.25 M NaCl. The total recovery of antibody was 65.56% with 2.91-fold purification, which was higher than that achieved by ammonium sulfate precipitation. This process simultaneously and effectively removed residual pepsin, high molecular weight aggregates and CA in the final F(ab')(2) product, and should be suitable for large-scale fractionation of therapeutic equine antivenoms.

Effects of Residual Lithium in the precursors of Li[Ni1/3Co1/3Mn1/3]O2 on their lithium-ion battery performance

Science.gov (United States)

Jo, Minsang; Ku, Heesuk; Park, Sanghyuk; Song, Junho; Kwon, Kyungjung

2018-07-01

Li[Ni1/3Co1/3Mn1/3]O2 cathode active materials are synthesized from co-precipitated hydroxide precursors Lix[Ni1/3Co1/3Mn1/3]1-x(OH)2, and the effect of residual Li in the precursors on the lithium-ion battery (LIB) performance of their corresponding cathode active materials is investigated. Three kinds of precursors that contain different amounts of Li are selected depending on different conditions of the solution composition for the co-precipitation and washing process. It is confirmed that the introduction of Li to the precursors reduces the degree of structural perfection by X-ray diffraction analysis. Undesirable cation mixing occurs with the increasing Li content of the precursors, which is inferred from a decline in lattice parameters and the calculated intensity ratio of (003) and (104) peaks. In the voltage range of 3.0-4.3 V, the initial charge/discharge capacities and the rate capability of the cathode active materials are aggravated when Li exists in the precursors. Therefore, it could be concluded that the strict control of Li in a solution for co-precipitation of precursors is necessary in the resynthesis of cathode active materials from spent LIBs.

Violaxanthin is an abscisic acid precursor in water-stressed dark-grown bean leaves

International Nuclear Information System (INIS)

Li, Yi; Walton, D.C.

1990-01-01

The leaves a dark-grown bean (Phaseolus vulgaris L.) seedlings accumulate considerably lower quantities of xanthophylls and carotenes than do leaves of light-grown seedlings, but they synthesize at least comparable amounts of abscisic acid (ABA) and its metabolites when water stressed. We observed a 1:1 relationship on a molar basis between the reduction in levels of ciolaxanthin, 9'-cis-neoxanthin, and 9-cis-violaxanthin and the accumulation of ABA, phaseic acid, and dihydrophaseic acid, when leaves from dark-grown plants were stressed for 7 hours. Early in the stress period, reductions in xanthophylls were greater than the accumulation of ABA and its metabolites, suggesting the accumulation of an intermediate which was subsequently converted to ABA. Leaves which were detached, but no stressed, did not accumulate ABA nor were their xanthophyll levels reduced. Leaves from plants that had been sprayed with cycloheximido did not accumulate ABA when stressed, nor were their xanthophyll levels reduced significantly. Incubation of dark-grown stressed leaves in an 18 O 2 -containing atmosphere resulted in the synthesis of ABA with levels of 18 O in the carboxyl group that were virtually identical to those observed in light-grown leaves. The results of these experiments indicate that violaxanthin is an ABA precursor in stressed dark-grown leaves, and they are used to suggest several possible pathways from violaxanthin to ABA

Violaxanthin is an abscisic acid precursor in water-stressed dark-grown bean leaves

Energy Technology Data Exchange (ETDEWEB)

Li, Yi; Walton, D.C. (State Univ. of New York, Syracuse (USA))

1990-03-01

The leaves a dark-grown bean (Phaseolus vulgaris L.) seedlings accumulate considerably lower quantities of xanthophylls and carotenes than do leaves of light-grown seedlings, but they synthesize at least comparable amounts of abscisic acid (ABA) and its metabolites when water stressed. We observed a 1:1 relationship on a molar basis between the reduction in levels of ciolaxanthin, 9{prime}-cis-neoxanthin, and 9-cis-violaxanthin and the accumulation of ABA, phaseic acid, and dihydrophaseic acid, when leaves from dark-grown plants were stressed for 7 hours. Early in the stress period, reductions in xanthophylls were greater than the accumulation of ABA and its metabolites, suggesting the accumulation of an intermediate which was subsequently converted to ABA. Leaves which were detached, but no stressed, did not accumulate ABA nor were their xanthophyll levels reduced. Leaves from plants that had been sprayed with cycloheximido did not accumulate ABA when stressed, nor were their xanthophyll levels reduced significantly. Incubation of dark-grown stressed leaves in an {sup 18}O{sub 2}-containing atmosphere resulted in the synthesis of ABA with levels of {sup 18}O in the carboxyl group that were virtually identical to those observed in light-grown leaves. The results of these experiments indicate that violaxanthin is an ABA precursor in stressed dark-grown leaves, and they are used to suggest several possible pathways from violaxanthin to ABA.

Precursors of nitrogenous disinfection by-products in drinking water--A critical review and analysis

Energy Technology Data Exchange (ETDEWEB)

Bond, Tom [Department of Civil and Environmental Engineering, Imperial College London, London SW7 2AZ (United Kingdom); Templeton, Michael R.; Graham, Nigel [Department of Civil and Environmental Engineering, Imperial College London, London SW7 2AZ (United Kingdom)

2012-10-15

Highlights: Black-Right-Pointing-Pointer The proportion of N-DBP formation attributable to specific precursors was calculated. Black-Right-Pointing-Pointer Precursor concentrations are typically insufficient to account for observed N-DBP formation, except CNX and NDMA. Black-Right-Pointing-Pointer Amino acid precursors are easier to remove during water treatment than suggested by laboratory studies. - Abstract: In recent years research into the formation of nitrogenous disinfection by-products (N-DBPs) in drinking water - including N-nitrosodimethylamine (NDMA), the haloacetonitriles (HANs), haloacetamides (HAcAms), cyanogen halides (CNX) and halonitromethanes (HNMs) - has proliferated. This is partly due to their high reported toxicity of N-DBPs. In this review paper information about the formation yields of N-DBPs from model precursors, and about environmental precursor occurrence, has been employed to assess the amount of N-DBP formation that is attributable to known precursors. It was calculated that for HANs and HAcAms, the concentrations of known precursors - mainly free amino acids are insufficient to account for the observed concentrations of these N-DBP groups. However, at least in some waters, a significant proportion of CNX and NDMA formation can be explained by known precursors. Identified N-DBP precursors tend to be of low molecular weight and low electrostatic charge relative to bulk natural organic matter (NOM). This makes them recalcitrant to removal by water treatment processes, notably coagulation, as confirmed by a number of bench-scale studies. However, amino acids have been found to be easier to remove during water treatment than would be suggested by the known molecular properties of the individual free amino acids.

Incorporation of radio-labelled nucleic acid precursors by Theileria parva in bovine blood and salivary glands of Rhipicephalus appendiculatus ticks

Energy Technology Data Exchange (ETDEWEB)

Irvin, A.D.; Boarer, C.D.H.; Kurtti, T.J.; Ocama, J.G.R. (International Lab. for Research on Animal Diseases, Nairobi (Kenya))

1981-12-01

The uptake of radio-labelled nucleic acid precursors by blood and tick salivary gland forms of Theileria parva was studied. Piroplasms took up tritiated purines, particularly hypoxanthine, but not pyrimidines. Similar uptake was recorded by T. parva, both in tick saliva and in salivary glands maintained in vitro. Intermediate parasite stages were those most readily labelled in glands; this reflected active nucleic acid synthesis associated with rapid parasite division. Radio-labelling of T. parva in tick salivary glands could be of value in procedures used for concentrating and purifying theilerial sporozoites.

Response of surface water chemistry to reduced levels of acid precipitation: Comparison of trends in two regions of New York, USA

Science.gov (United States)

Burns, Douglas A.; McHale, M.R.; Driscoll, C.T.; Roy, K.M.

2006-01-01

In light of recent reductions in sulphur (S) and nitrogen (N) emissions mandated by Title IV of the Clean Air Act Amendments of 1990, temporal trends and trend coherence in precipitation (1984-2001 and 1992-2001) and surface water chemistry (1992-2001) were determined in two of the most acid-sensitive regions of North America, i.e. the Catskill and Adirondack Mountains of New York. Precipitation chemistry data from six sites located near these regions showed decreasing sulphate (SO42-), nitrate (NO3-), and base cation (CB) concentrations and increasing pH during 1984-2001, but few significant trends during 1992-2001. Data from five Catskill streams and 12 Adirondack lakes showed decreasing trends in SO42- concentrations at all sites, and decreasing trends in NO3-, CB, and H+ concentrations and increasing trends in dissolved organic carbon at most sites. In contrast, acid-neutralizing capacity (ANC increased significantly at only about half the Adirondack lakes and in one of the Catskill streams. Flow correction prior to trend analysis did not change any trend directions and had little effect on SO42- trends, but it caused several significant non-flow-corrected trends in NO3- and ANC to become non-significant, suggesting that trend results for flow-sensitive constituents are affected by flow-related climate variation. SO42- concentrations showed high temporal coherence in precipitation, surface waters, and in precipitation-surface water comparisons, reflecting a strong link between S emissions, precipitation SO42- concentrations, and the processes that affect S cycling within these regions. NO3- and H+ concentrations and ANC generally showed weak coherence, especially in surface waters and in precipitation-surface water comparisons, indicating that variation in local-scale processes driven by factors such as climate are affecting trends in acid-base chemistry in these two regions. Copyright ?? 2005 John Wiley & Sons, Ltd.

Synthesis of aqueous suspensions of magnetic nanoparticles with the co-precipitation of iron ions in the presence of aspartic acid

Energy Technology Data Exchange (ETDEWEB)

Pušnik, Klementina; Goršak, Tanja [Department for Materials Synthesis, Jožef Stefan Institute, 1000 Ljubljana (Slovenia); Jožef Stefan International Postgraduate School, 1000 Ljubljana (Slovenia); Drofenik, Miha [Department for Materials Synthesis, Jožef Stefan Institute, 1000 Ljubljana (Slovenia); Faculty of Chemistry and Chemical Engineering, University of Maribor, 2000 Maribor (Slovenia); Makovec, Darko [Department for Materials Synthesis, Jožef Stefan Institute, 1000 Ljubljana (Slovenia); Jožef Stefan International Postgraduate School, 1000 Ljubljana (Slovenia)

2016-09-01

There is increasing demand for the production of large quantities of aqueous suspensions of magnetic iron-oxide nanoparticles. Amino acids are one possible type of inexpensive, nontoxic, and biocompatible molecules that can be used as the surfactants for the preparation of stable suspensions. This preparation can be conducted in a simple, one-step process based on the co-precipitation of Fe{sup 3+}/Fe{sup 2+} ions in the presence of the amino acid. However, the presence of this amino acid changes the mechanism of the magnetic nanoparticles' formation. In this investigation we analyzed the influence of aspartic amino acid (Asp) on the formation of magnetic iron-oxide nanoparticles during the co-precipitation. The process of the nanoparticles’ formation was followed using a combination of TEM, x-ray diffractometry, magnetic measurements, in-situ FT-IR spectroscopy, and chemical analysis, and compared with the formation of nanoparticles without the Asp. The Asp forms a coordination complex with the Fe{sup 3+} ions, which impedes the formation of the intermediate iron oxyhydroxide phase and suppresses the growth of the final magnetic iron-oxide nanoparticles. Slower reaction kinetics can lead to the formation of nonmagnetic secondary phases. The aspartic-acid-absorbed nanoparticles can be dispersed to form relatively concentrated aqueous suspensions displaying a good colloidal stability at an increased pH. - Highlights: • Co-precipitation of Fe{sup 3+}/Fe{sup 2+} ions in the presence of aspartic amino acid (Asp). • Through analysis of nanoparticle formation mechanism. • Presence of Asp changes the mechanism of the nanoparticles’ formation. • Asp forms a coordination complex with the Fe{sup 3+} ions. • Asp impedes the formation of iron oxyhydroxide phase and suppresses the growth of iron-oxide nanoparticles. • The aspartic-acid-absorbed nanoparticles form stable aqueous suspensions.

Synthesis of aqueous suspensions of magnetic nanoparticles with the co-precipitation of iron ions in the presence of aspartic acid

International Nuclear Information System (INIS)

Pušnik, Klementina; Goršak, Tanja; Drofenik, Miha; Makovec, Darko

2016-01-01

There is increasing demand for the production of large quantities of aqueous suspensions of magnetic iron-oxide nanoparticles. Amino acids are one possible type of inexpensive, nontoxic, and biocompatible molecules that can be used as the surfactants for the preparation of stable suspensions. This preparation can be conducted in a simple, one-step process based on the co-precipitation of Fe 3+ /Fe 2+ ions in the presence of the amino acid. However, the presence of this amino acid changes the mechanism of the magnetic nanoparticles' formation. In this investigation we analyzed the influence of aspartic amino acid (Asp) on the formation of magnetic iron-oxide nanoparticles during the co-precipitation. The process of the nanoparticles’ formation was followed using a combination of TEM, x-ray diffractometry, magnetic measurements, in-situ FT-IR spectroscopy, and chemical analysis, and compared with the formation of nanoparticles without the Asp. The Asp forms a coordination complex with the Fe 3+ ions, which impedes the formation of the intermediate iron oxyhydroxide phase and suppresses the growth of the final magnetic iron-oxide nanoparticles. Slower reaction kinetics can lead to the formation of nonmagnetic secondary phases. The aspartic-acid-absorbed nanoparticles can be dispersed to form relatively concentrated aqueous suspensions displaying a good colloidal stability at an increased pH. - Highlights: • Co-precipitation of Fe 3+ /Fe 2+ ions in the presence of aspartic amino acid (Asp). • Through analysis of nanoparticle formation mechanism. • Presence of Asp changes the mechanism of the nanoparticles’ formation. • Asp forms a coordination complex with the Fe 3+ ions. • Asp impedes the formation of iron oxyhydroxide phase and suppresses the growth of iron-oxide nanoparticles. • The aspartic-acid-absorbed nanoparticles form stable aqueous suspensions.

Synthesis of alumina/YAG 20 vol% composite by co-precipitation

Directory of Open Access Journals (Sweden)

Radosław Lach

2011-12-01

Full Text Available Co-precipitation of alumina/YAG precursor from aluminum and yttrium nitrate solution with ammonium carbonate results in dawsonite. Its crystallographic parameters differ from the compound precipitated with no yttrium additive. It suggests that yttrium ions become incorporated into the dawsonite structure. The DSC/TG and X-ray diffraction measurements show decomposition of dawsonite at elevated temperatures resulting in γ-Al2O3 and then δ- and θ-alumina modifications. Full transformation to α-Al2O3 and YAG occurs at temperatures higher than 1230°C. Starting powder for the sintering experiments was prepared using the coprecipitated precursor calcined at 600°C. Seeding of such powder with 5 wt.% α-Al2O3 results in material of 98% density at 1500°C. Much lower densification show compacts of unseeded powder.

Acid-functionalized polyolefin materials and their use in acid-promoted chemical reactions

Science.gov (United States)

Oyola, Yatsandra; Tian, Chengcheng; Bauer, John Christopher; Dai, Sheng

2016-06-07

An acid-functionalized polyolefin material that can be used as an acid catalyst in a wide range of acid-promoted chemical reactions, wherein the acid-functionalized polyolefin material includes a polyolefin backbone on which acid groups are appended. Also described is a method for the preparation of the acid catalyst in which a precursor polyolefin is subjected to ionizing radiation (e.g., electron beam irradiation) of sufficient power and the irradiated precursor polyolefin reacted with at least one vinyl monomer having an acid group thereon. Further described is a method for conducting an acid-promoted chemical reaction, wherein an acid-reactive organic precursor is contacted in liquid form with a solid heterogeneous acid catalyst comprising a polyolefin backbone of at least 1 micron in one dimension and having carboxylic acid groups and either sulfonic acid or phosphoric acid groups appended thereto.

Precursors of nitrogenous disinfection by-products in drinking water––A critical review and analysis

International Nuclear Information System (INIS)

Bond, Tom; Templeton, Michael R.; Graham, Nigel

2012-01-01

Highlights: ► The proportion of N-DBP formation attributable to specific precursors was calculated. ► Precursor concentrations are typically insufficient to account for observed N-DBP formation, except CNX and NDMA. ► Amino acid precursors are easier to remove during water treatment than suggested by laboratory studies. - Abstract: In recent years research into the formation of nitrogenous disinfection by-products (N-DBPs) in drinking water – including N-nitrosodimethylamine (NDMA), the haloacetonitriles (HANs), haloacetamides (HAcAms), cyanogen halides (CNX) and halonitromethanes (HNMs) – has proliferated. This is partly due to their high reported toxicity of N-DBPs. In this review paper information about the formation yields of N-DBPs from model precursors, and about environmental precursor occurrence, has been employed to assess the amount of N-DBP formation that is attributable to known precursors. It was calculated that for HANs and HAcAms, the concentrations of known precursors – mainly free amino acids are insufficient to account for the observed concentrations of these N-DBP groups. However, at least in some waters, a significant proportion of CNX and NDMA formation can be explained by known precursors. Identified N-DBP precursors tend to be of low molecular weight and low electrostatic charge relative to bulk natural organic matter (NOM). This makes them recalcitrant to removal by water treatment processes, notably coagulation, as confirmed by a number of bench-scale studies. However, amino acids have been found to be easier to remove during water treatment than would be suggested by the known molecular properties of the individual free amino acids.

Continuous precipitation process of plutonium salts

International Nuclear Information System (INIS)

Richard, P.

1967-03-01

This work concerns the continuous precipitation process of plutonium oxalate. Investigations about the solubility of different valence states in nitric-oxalic and in nitric-sulfuric-oxalic medium lead to select the precipitation process of tetravalent plutonium oxalate. Settling velocity and granulometry of tetravalent oxalate plutonium have been studied with variation of several precipitation parameters such as: temperature, acidity, excess of oxalic acid and aging time. Then are given test results of some laboratory continuous apparatus. Conditions of operation with adopted tubular apparatus are defined in conclusion. A flow-sheet is given for a process at industrial scale. (author) [fr

Kinetic study of the precipitation of radioactive elements in the production process of phosphoric acid

International Nuclear Information System (INIS)

Ben Mahmoud, Souha

2009-01-01

In this engineering study we determined the activities of gamma emitting radionuclides belonging to the families of 238 U , 232 Th and 40K in phosphate, the acid derivatives and gypsum in Tunisian Chemical Group. The most important activities are those of 238 U and 226 Ra, which are located in the phosphate, gypsum and the precipitates formed in the pipes.

Facile synthesis of a conjugation-grafted-TiO{sub 2} nanohybrid with enhanced visible-light photocatalytic properties from nanotube titanic acid precursors

Energy Technology Data Exchange (ETDEWEB)

Guo, Yanru; Zhang, Min, E-mail: zm1012@henu.edu.cn; Zhang, Zhihua; Li, Qiuye; Yang, Jianjun [Henan University, National and Local Joint Engineering Research Center for Applied Technology of Hybrid Nanomaterials (China)

2016-08-15

A conjugation-grafted-TiO{sub 2} nanohybrid was synthesized by chemically grafting conjugated structures on the surface of nanotube titanic acid (NTA) precursor-based TiO{sub 2} through the controlled thermal degradation of a coacervated polymer layer of polyvinyl alcohol (PVA). The interfacial interactions between the NTA precursor-based TiO{sub 2} and conjugated structures were characterized using Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Moreover, the effects of the NTA’s pretreatment temperature and the weight ratio of NTA to PVA on the photocatalytic degradation of methyl orange were also investigated. A higher NTA pretreatment temperature and a lower NTA to PVA weight ratio were found to enhance photogenerated electron–hole separation efficiency and photocatalytic activity. Moreover, the conjugation-grafted-TiO{sub 2} nanohybrid synthesized from the NTA precursor displayed a much higher visible-light photocatalytic activity than that of the sample obtained from the P25 precursor. The origin of the enhanced photocatalytic activity under visible-light irradiation is also discussed in detail.

Biosynthesis of l-Ascorbic Acid and Conversion of Carbons 1 and 2 of l-Ascorbic Acid to Oxalic Acid Occurs within Individual Calcium Oxalate Crystal Idioblasts1

Science.gov (United States)

Kostman, Todd A.; Tarlyn, Nathan M.; Loewus, Frank A.; Franceschi, Vincent R.

2001-01-01

l-Ascorbic acid (AsA) and its metabolic precursors give rise to oxalic acid (OxA) found in calcium oxalate crystals in specialized crystal idioblast cells in plants; however, it is not known if AsA and OxA are synthesized within the crystal idioblast cell or transported in from surrounding mesophyll cells. Isolated developing crystal idioblasts from Pistia stratiotes were used to study the pathway of OxA biosynthesis and to determine if idioblasts contain the entire path and are essentially independent in OxA synthesis. Idioblasts were supplied with various 14C-labeled compounds and examined by micro-autoradiography for incorporation of 14C into calcium oxalate crystals. [14C]OxA gave heavy labeling of crystals, indicating the isolated idioblasts are functional in crystal formation. Incubation with [1-14C]AsA also gave heavy labeling of crystals, whereas [6-14C]AsA gave no labeling. Labeled precursors of AsA (l-[1-14C]galactose; d-[1-14C]mannose) also resulted in crystal labeling, as did the ascorbic acid analog, d-[1-14C]erythorbic acid. Intensity of labeling of isolated idioblasts followed the pattern OxA > AsA (erythorbic acid) > l-galactose > d-mannose. Our results demonstrate that P. stratiotes crystal idioblasts synthesize the OxA used for crystal formation, the OxA is derived from the number 1 and 2 carbons of AsA, and the proposed pathway of ascorbic acid synthesis via d-mannose and l-galactose is operational in individual P. stratiotes crystal idioblasts. These results are discussed with respect to fine control of calcium oxalate precipitation and the concept of crystal idioblasts as independent physiological compartments. PMID:11161021

Improvement of the antifungal activity of lactic acid bacteria by addition to the growth medium of phenylpyruvic acid, a precursor of phenyllactic acid.

Science.gov (United States)

Valerio, Francesca; Di Biase, Mariaelena; Lattanzio, Veronica M T; Lavermicocca, Paola

2016-04-02

The aim of the current study was to improve the antifungal activity of eight lactic acid bacterial (LAB) strains by the addition of phenylpyruvic acid (PPA), a precursor of the antifungal compound phenyllactic acid (PLA), to a defined growth medium (DM). The effect of PPA addition on the LABs antifungal activity related to the production of organic acids (PLA, d-lactic, l-lactic, acetic, citric, formic and 4-hydroxy-phenyllactic acids) and of other phenylpyruvic-derived molecules, was investigated. In the presence of PPA the inhibitory activity (expressed as growth inhibition percentage) against fungal bread contaminants Aspergillus niger and Penicillium roqueforti significantly increased and was, even if not completely, associated to PLA increase (from a mean value of 0.44 to 0.93 mM). While the inhibitory activity against Endomyces fibuliger was mainly correlated to the low pH and to lactic, acetic and p-OH-PLA acids. When the PCA analysis based on data of growth inhibition percentage and organic acid concentrations was performed, strains grown in DM+PPA separated from those grown in DM and the most active strains Lactobacillus plantarum 21B, Lactobacillus fermentum 18B and Lactobacillus brevis 18F grouped together. The antifungal activity resulted to be strain-related, based on a different mechanism of action for filamentous fungi and the yeast and was not exclusively associated to the increase of PLA. Therefore, a further investigation on the unique unidentified peak in HPLC-UV chromatograms, was performed by LC-MS/MS analysis. Actually, full scan mass spectra (negative ion mode) recorded at the retention time of the unknown compound, showed a main peak of m/z 291.0 which was consistent with the nominal mass of the molecular ion [M-H](-) of polyporic acid, a PPA derivative whose antifungal activity has been previously reported (Brewer et al., 1977). In conclusion, the addition of PPA to the growth medium contributed to improve the antifungal activity of LAB

Study of precipitation in Al–Mg–Si Alloys by atom probe tomography II. Influence of Cu additions

International Nuclear Information System (INIS)

Zandbergen, M.W.; Cerezo, A.; Smith, G.D.W.

2015-01-01

Atom probe tomography (APT) analysis and hardness measurements have been used to characterise the early stages of precipitation in three Al–Mg–Si alloys with different Cu contents (Al–0.51 at.%Mg–0.94 at.%Si, with 0.01 at.%, 0.06 at.%, or 0.34 at.% Cu). A range of single and multi- stage heat treatments were chosen to evaluate the changes in precipitation processes. Three ageing temperatures were investigated, 298 K (natural ageing), 353 K (pre-ageing) and 453 K (automotive paint-bake conditions). The Cu content had significant effects on the microstructural evolution within the alloy. Formation of clusters which can act as precursors of elongated precipitates during paint-baking was found to be enhanced with increasing Cu content. This improved the paint-bake hardening response and mitigated the deleterious effects of natural ageing. Cu was present in all precipitates in the highest Cu-containing alloy. These precipitates were believed to be precursors to the Q′ phase. Mechanisms for the effects of Cu on precipitation kinetics are proposed.

Removal of sulfamic acid from plutonium sulfamate--sulfamic acid solution

International Nuclear Information System (INIS)

Gray, L.W.

1978-10-01

Plutonium metal can be readily dissolved in aqueous solutions of sulfamic acid. When the plutonium sulfamate--sulfamic acid solutions are added to normal purex process streams, the sulfamate ion is oxidized by addition of sodium nitrite. This generates sodium sulfate which must be stored as radioactive waste. When recovery of ingrown 241 Am or storage of the dissolved plutonium must be considered, the sulfamate ion poses major and undesirable precipitation problems in the process streams. The present studies show that 40 to 80% of the sulfamate present in the dissolver solutions can be removed by precipitation as sulfamic acid by the addition of concentrated nitric acid. Addition of 64% nitric acid allows precipitation of 40 to 50% of the sulfamate; addition of 72% nitric acid allows precipitation of 50 to 60% of the sulfamate. If the solutions are chilled, additional sulfamic acid will precipitate. If the solutions are chilled to -10 0 C, about 70 to 80% of the orginal sulfamic acid in the dissolver will precipitate. A single, low-volume wash of the sulfamic acid crystals with concentrated nitric acid will decontaminate the crystals to a plutonium content of 5 dis/(min-gram)

Preparation of morphology controlled Th1-xUxO2 sintered pellets from low-temperature precursors

International Nuclear Information System (INIS)

Clavier, N.; Dacheux, N.; Podor, R.; Hingant, N.; Clavier, N.; Dacheux, N.; Hubert, S.; Barre, N.; Podor, R.; Aranda, L.

2011-01-01

Dense sintered samples of Th 1 - x U x O 2 solid solutions were prepared from the initial precipitation of oxalate precursors through two different wet chemical routes, based either on the direct precipitation of the cations or on the use of hydrothermal method. For both low-temperature precursors, the specific surface area was followed versus the heating temperature and the influence of the conversion step on the oxide powder reactivity was evidenced since it allowed to obtain reactive surfaces in the range of 15-45 m 2 g -1 without any additional grinding step. From dilatometric studies, the operating conditions required for the complete densification of the Th 1 - x U x O 2 pellets were set to a heat treatment of 3 h at 1500 degrees C. In these conditions, the density of the samples lies between 94% and 99% of the calculated value whatever the preparation method chosen which appeared very promising compared to the results already reported under inert atmosphere. The initial precipitation of low-temperature precursors thus allowed to lower the sintering temperature by about 100 degrees C while the use of hydrothermal conditions significantly improved the cationic distribution in the sintered samples, as shown from EPMA statistical experiments. (authors)

Influence of commercial (Fluka) naphthenic acids on acid volatile sulfide (AVS) production and divalent metal precipitation.

Science.gov (United States)

McQueen, Andrew D; Kinley, Ciera M; Rodgers, John H; Friesen, Vanessa; Bergsveinson, Jordyn; Haakensen, Monique C

2016-12-01

Energy-derived waters containing naphthenic acids (NAs) are complex mixtures often comprising a suite of potentially problematic constituents (e.g. organics, metals, and metalloids) that need treatment prior to beneficial use, including release to receiving aquatic systems. It has previously been suggested that NAs can have biostatic or biocidal properties that could inhibit microbially driven processes (e.g. dissimilatory sulfate reduction) used to transfer or transform metals in passive treatment systems (i.e. constructed wetlands). The overall objective of this study was to measure the effects of a commercially available (Fluka) NA on sulfate-reducing bacteria (SRB), production of sulfides (as acid-volatile sulfides [AVS]), and precipitation of divalent metals (i.e. Cu, Ni, Zn). These endpoints were assessed following 21-d aqueous exposures of NAs using bench-scale reactors. After 21-days, AVS molar concentrations were not statistically different (pAVS production was sufficient in all NA treatments to achieve ∑SEM:AVS AVS) could be used to treat metals occurring in NAs affected waters. Copyright © 2016 Elsevier Inc. All rights reserved.

Review on hydroxylamine, a precursor to amino-acids

Science.gov (United States)

Lemaire, Jean Louis

2015-08-01

Does life on earth come from interstellar space (IS)?It has been recently demonstrated that part of the terrestrial water is of IS origin [Cleeves et al. Science 2014]. This raises the question whether materials like amino-acids or their pre-biotic molecular precursors could have been formed and brought to earth in the same way than water. Another question is whether these molecules were formed in the gas phase or through reactions on the surface/volume of ice-covered grains. This may then have occurred in the vicinity of proto-stellar cores or deep into a pristine dense molecular clouds at very low temperatures.As far as bio-related molecules are concerned, chemistry with nitrogen-bearing molecules (like NH3 and NO) is involved. I review recent experimental work showing that hydroxylamine (NH2OH) could be formed either by surface or by volume reactions in conditions close to those prevailing in dense media. They use either electron-UV irradiation of water-ammonia ices [Zheng & Kaiser JCPA 2010] or successive hydrogenation of solid nitric oxide[Congiu, Fedoseev & al. ApJL.2012] or the simple oxidation of ammonia [He, Vidali, Lemaire & Garrod, ApJ, 2015] or the reaction of ammonia with hydroxyl radicals in a rare gas matrix [Zins & Krim, 2014, 69th ISMS]. A step further, the synthesis of the simplest amino-acids, glycine (NH2CH2COOH) and L- or D-alanine (NH2CH3CHCOOH) has already been obtained via reactions in the gas phase involving NH2OH+ [Blagojevic & al. MNRAS 2003].In addition to several earlier models demonstrating that the formation of all these molecules is possible in the gas phase, a new recent three-phase gas-grain chemical kinetics model of hot cores [Garrod ApJ 2013] shows that the results of ammonia oxidation we obtain are plausible by surface/volume reactions.Although none of the aforementioned molecules (except glycine in a sample of cometary origin) has been yet detected in the IS, they all are considered by many observers and modelers as likely

Study On Precipitation Of UO2 Ex-AUC Powder. Part I: Precipitation Of AUC By (NH4)2CO3 From Uranyl Fluoride Solution

International Nuclear Information System (INIS)

Nguyen Trong Hung; Le Ba Thuan; Do Van Khoai; Nguyen Thanh Thuy; Nguyen Van Tung

2011-01-01

In this paper, Ammonium Uranyl Carbonate (AUC) powders were prepared by precipitation method in solution. UO 2 F 2 /HF, ammonium carbonate (AC), and ammonium hydroxide solution were used as precursors for precipitation. The influence of C/U ratio (mol/mol), AC concentration (g/L), reaction temperature ( o C), on characteristics of AUC powders was also investigated. Then, the synthesized AUC powders were analyzed (to define) phase composition (X-ray), fluorine content, morphology (by SEM), and specific surface area (BET). (author)

Adirondack tourism: perceived consequences of acid rain

Energy Technology Data Exchange (ETDEWEB)

Metz, W.C.

1984-03-01

This report seeks to place in perspective the perceived effects of acid precipitation on the tourist industry in the Adirondacks. The 9375-square mile park is host to almost nine million tourists annually, not including seasonal residents. Since the park was established almost 100 years ago, there have been many changes in tourist characteristics, available recreational facilities, kinds of activities, accessibility of the area, and land use and resource management policies. The tourist industry has been influenced by both controllable and uncontrollable factors. At present the overwhelming majority of recreational opportunities and natural resources important to the Adirondack tourist industry are relatively unaffected by acid precipitation. Fishing, a significant component of the tourist industry, is the most vulnerable, but any presumed adverse economic effect has to be weighed against the location of the impacted waters, total Adirondack fishing habitat, substitution available, habitat usage, fisherman characteristics, resource management, and the declining importance of fishing as an Adirondack recreational attraction. Concern is expressed as to whether present minimal acidification impacts are the precursor of major future impacts on Adirondack terrestrial and aquatic environments, and ultimately tourism. Tourism in the Adirondacks is increasing, while many other regional employment sectors are declining. It is becoming a more stable multiseason industry. Its future growth and character will be affected by government, private organization, business community, and resident controversies regarding land use and resource management attitudes, policies, budgets, and regulations. The acid precipitation issue is only one of many related controversies. 65 references, 2 figures.

Precursors and metabolic pathway for guaiacol production by Alicyclobacillus acidoterrestris.

Science.gov (United States)

Cai, Rui; Yuan, Yahong; Wang, Zhouli; Guo, Chunfeng; Liu, Bin; Liu, Laping; Wang, Yutang; Yue, Tianli

2015-12-02

Alicyclobacillus acidoterrestris has recently received much attention due to its implication in the spoilage of pasteurized fruit juices, which was manifested by the production of guaiacol. Vanillic acid and vanillin have been accepted as the biochemical precursors of guaiacol in fruit juices. The purpose of this study was to try to find other precursors and elucidate details about the conversion of vanillic acid and vanillin to guaiacol by A. acidoterrestris. Four potential substrates including ferulic acid, catechol, phenylalanine and tyrosine were analyzed, but they could not be metabolized to guaiacol by all the thirty A. acidoterrestris strains tested. Resting cell studies and enzyme assays demonstrated that vanillin was reduced to vanillyl alcohol by NADPH-dependent vanillin reductase and oxidized to vanillic acid by NAD(P)(+)-dependent vanillin dehydrogenases in A. acidoterrestris DSM 3923. Vanillic acid underwent a nonoxidative decarboxylation to guaiacol. The reversible vanillic acid decarboxylase involved was oxygen insensitive and pyridine nucleotide-independent. Copyright © 2015. Published by Elsevier B.V.

The incorporation of radio-labelled nucleic acid precursors by Theileria parva in bovine blood and salivary glands of Rhipicephalus appendiculatus ticks

International Nuclear Information System (INIS)

Irvin, A.D.; Boarer, C.D.H.; Kurtti, T.J.; Ocama, J.G.R.

1981-01-01

The uptake of radio-labelled nucleic acid precursors by blood and tick salivary gland forms of Theileria parva was studied. Piroplasms took up tritiated purines, particularly hypoxanthine, but not pyrimidines. Similar uptake was recorded by T. parva, both in tick saliva and in salivary glands maintained in vitro. Intermediate parasite stages were those most readily labelled in glands; this reflected active nucleic acid synthesis associated with rapid parasite division. Radio-labelling of T. parva in tick salivary glands could be of value in procedures used for concentrating and purifying theilerial sporozoites. (author)

Separation and Precipitation of Nickel from Acidic Sulfate Leaching Solution of Molybdenum-Nickel Black Shale by Potassium Nickel Sulfate Hexahydrate Crystallization

Science.gov (United States)

Deng, Zhigan; Wei, Chang; Fan, Gang; Li, Xingbin; Li, Minting; Li, Cunxiong

2018-02-01

Nickel was separated and precipitated with potassium nickel sulfate hexahydrate [K2Ni(SO4)2·6H2O] from acidic sulfate solution, a leach solution from molybdenum-nickel black shale. The effects of the potassium sulfate (K2SO4) concentration, crystallization temperature, solution pH, and crystallization time on nickel(II) recovery and iron(III) precipitation were investigated, revealing that nickel and iron were separated effectively. The optimum parameters were K2SO4 concentration of 200 g/L, crystallization temperature of 10°C, solution pH of 0.5, and crystallization time of 24 h. Under these conditions, 97.6% nickel(II) was recovered as K2Ni(SO4)2·6H2O crystals while only 2.0% of the total iron(III) was precipitated. After recrystallization, 98.4% pure K2Ni(SO4)2·6H2O crystals were obtained in the solids. The mother liquor was purified by hydrolysis-precipitation followed by cooling, and more than 99.0% K2SO4 could be crystallized. A process flowsheet was developed to separate iron(III) and nickel(II) from acidic-sulfate solution.

De novo and salvage pathway precursor incorporation during DNA replication at the nuclear matrix

International Nuclear Information System (INIS)

Panzeter, P.L.

1988-01-01

Total nuclear DNA can be empirically subdivided into low salt-soluble (LS) DNA (75-80%), high salt-soluble (HS) DNA (18-23%), and nuclear matrix-associated (NM) DNA which remains tightly bound to the nuclear matrix (∼2%). The most-newly replicated DNA is that associated with the nuclear matrix in regenerating rat liver. Analyses of the DNA fractions after various pulse times revealed that the salvage and de novo pathway DNA precursors investigated were incorporated preferentially into NM-DNA at early pulse times, after which the radioactivity became progressively incorporated into HS- and LS-DNA, respectively. These results support two models of nuclear matrix-associated DNA replication, proposed previously, and a third model presented in this dissertation. In addition, the incorporation of de novo pathway precursors lagged significantly (> 10 minutes) behind the incorporation of precursors entering through the salvage pathway. Channeling of salvage pathway precursors to DNA replication sites would explain the more rapid uptake of salvage precursors into NM-DNA than de novo precursors. To investigate the possibility of this heretofore in vitro phenomenon, the incorporation of the salvage precursor, ( 3 H)deoxythymidine, and the de novo precursor, ( 14 C)orotic acid, into NM-DNA and dTTP was examined in regenerating rat liver. There was no significant difference between the incorporation pattern of ( 14 C)orotic acid into NM-DNA thymine and that of ( 14 C)orotic acid into soluble dTTP. Contrastingly, the salvage pathway precursor, ( 3 H)deoxythymidine, labeled NM-DNA before labeling the dTTP pool

Investigation of Neptunium Precipitator Cleanout Options

International Nuclear Information System (INIS)

Hill, B.C.

2003-01-01

Oxalate precipitation followed by filtration is used to prepare plutonium oxalate. Historically, plutonium oxalate has tended to accumulate in the precipitation tanks. These solids are periodically removed by flushing with concentrated (64 percent) nitric acid. The same precipitation tanks will now be used in the processing of neptunium. Literature values indicate that neptunium oxalate may not be as soluble as plutonium oxalate in nitric acid. Although a wide variety of options is available to improve neptunium oxalate solubility for precipitator flushing, most of these options are not practical for use. Many of these options require the use of incompatible or difficult to handle chemicals. Other options would require expensive equipment modifications or are likely to lead to product contamination. Based on review of literature and experimental results, the two best options for flushing the precipitator are (1) 64 percent nitric acid and (2) addition of sodium permanganate follow ed by sodium nitrite. Nitric acid is the easiest option to implement. It is already used in the facility and will not lead to product contamination. Experimental results indicate that neptunium oxalate can be dissolved in concentrated nitric acid (64 percent) at 60 degree C to a concentration of 2.6 to 5.6 grams of Np/liter after at least three hours of heating. A lower concentration (1.1 grams of Np/liter) was measured at 60 degree C after less than two hours of heating. These concentrations are acceptable for flushing if precipitator holdup is low (approximately 100-250 grams), but a second method is required for effective flushing if precipitator holdup is high (approximately 2 kilograms). The most effective method for obtaining higher neptunium concentrations is the use of sodium permanganate followed by the addition of sodium nitrite. There is concern that residual manganese from these flushes could impact product purity. Gas generation during permanganate addition is also a concern

Radiosynthesis of [18F]fluorophenyl-L-amino acids by isotopic exchange on carbonyl-activated precursors

International Nuclear Information System (INIS)

Castillo Melean, Johnny

2011-01-01

Aromatic [ 18 F]fluoroamino acids have earlier been developed as promising probes for diagnostics using PET. However, a wider use of these radiofluorinated compounds has been limited due to radiosynthetic constraints. The work here presents an amenable three-step radiosynthesis pathway for the preparation of 2-[ 18 F]fluoro-L-phenylalanine (2-[ 18 F]Fphe), 2-[ 18 F]fluoro-L-tyrosine (2-[ 18 F]Ftyr), 6-[ 18 F]fuoro-L-m-tyrosine (6-[ 18 F]Fmtyr) and 6-[ 18 F]fluoro-L-DOPA (6-[ 18 F]FDOPA). For this, corresponding precursors were 18 F-fluorinated by nucleophilic isotopic exchange, followed by either removal of an activating formyl group with Rh(PPh 3 ) 3 Cl or its conversion by Baeyer-Villiger oxidation, respectively, and subsequent hydrolysis of protecting groups in acidic medium. Two efficient synthetic approaches were developed for the preparation of highly functionalized fluoro-benzaldehydes and -ketones which were used as labeling precursors. The compounds (2S,5S)-tert-butyl 2-tert-butyl-5-(2-fluoro-5-formylbenzyl)-3-methyl-4-oxoimidazolidine-1 -carboxylate (1a), (2S,5S)-tert-butyl 5-(5-acetyl-2-fluorobenzyl)-2-tert-butyl-3-methyl-4-oxoimidazolidine-1 -carboxylate (1c), (2S,5S)-benzyl 2-tert-butyl-5-(2-fluoro-5-formylbenzyl)-3-methyl-4-oxoimidazolidine-1 -carbo-xylate (1d), 4-fluoro-3-(((2S,5R)-5-isopropyl-3,6-dimethoxy-2,5-dihydropyrazin-2-yl) me-thyl)b enzal-dehyde (1e) and 1-(4-fluoro-3-(((2S,5R)-5-isopropyl-3,6-dimethoxy-2,5-dihydropyrazin-2-yl) me-thy l)phenyl)ethanone (1f), could be prepared in six steps and overall yields of 41%, 48%, 37%, 27%, and 32%, respectively. (2S,5S)-tert-Butyl 5-(4-(benzyloxy)-2-fluoro-5-formylbenzyl)-2-tert-butyl-3-methyl-4 -oxoimidazolidi ne-1-carboxylate (1b) was prepared in ten steps with an overall yield of 19% while compounds (2S,5S)-tert-butyl 5-(5-(3,5-bis(trifluoromethyl)-benzoyl)-2-fluorobenzyl)-2-tert-butyl-3 -methyl-4-oxoimidazolidine-1-carboxylate (1g) and (2S,5S)-tert-butyl 2-tert-butyl-5-(2-fluoro-5

Lactic acid induces aberrant amyloid precursor protein processing by promoting its interaction with endoplasmic reticulum chaperone proteins.

Directory of Open Access Journals (Sweden)

Yiwen Xiang

Full Text Available BACKGROUND: Lactic acid, a natural by-product of glycolysis, is produced at excess levels in response to impaired mitochondrial function, high-energy demand, and low oxygen availability. The enzyme involved in the production of β-amyloid peptide (Aβ of Alzheimer's disease, BACE1, functions optimally at lower pH, which led us to investigate a potential role of lactic acid in the processing of amyloid precursor protein (APP. METHODOLOGY/PRINCIPAL FINDINGS: Lactic acid increased levels of Aβ40 and 42, as measured by ELISA, in culture medium of human neuroblastoma cells (SH-SY5Y, whereas it decreased APP metabolites, such as sAPPα. In cell lysates, APP levels were increased and APP was found to interact with ER-chaperones in a perinuclear region, as determined by co-immunoprecipitation and fluorescence microscopy studies. Lactic acid had only a very modest effect on cellular pH, did increase the levels of ER chaperones Grp78 and Grp94 and led to APP aggregate formation reminiscent of aggresomes. CONCLUSIONS/SIGNIFICANCE: These findings suggest that sustained elevations in lactic acid levels could be a risk factor in amyloidogenesis related to Alzheimer's disease through enhanced APP interaction with ER chaperone proteins and aberrant APP processing leading to increased generation of amyloid peptides and APP aggregates.

Formic and Acetic Acid Observations over Colorado by Chemical Ionization Mass Spectrometry and Organic Acids' Role in Air Quality

Science.gov (United States)

Treadaway, V.; O'Sullivan, D. W.; Heikes, B.; Silwal, I.; McNeill, A.

2015-12-01

Formic acid (HFo) and acetic acid (HAc) have both natural and anthropogenic sources and a role in the atmospheric processing of carbon. These organic acids also have an increasing importance in setting the acidity of rain and snow as precipitation nitrate and sulfate concentrations have decreased. Primary emissions for both organic acids include biomass burning, agriculture, and motor vehicle emissions. Secondary production is also a substantial source for both acids especially from biogenic precursors, secondary organic aerosols (SOAs), and photochemical production from volatile organic compounds (VOCs) and oxygenated volatile organic compounds (OVOCs). Chemical transport models underestimate organic acid concentrations and recent research has sought to develop additional production mechanisms. Here we report HFo and HAc measurements during two campaigns over Colorado using the peroxide chemical ionization mass spectrometer (PCIMS). Iodide clusters of both HFo and HAc were recorded at mass-to-charge ratios of 173 and 187, respectively. The PCIMS was flown aboard the NCAR Gulfstream-V platform during the Deep Convective Clouds and Chemistry Experiment (DC3) and aboard the NCAR C-130 during the Front Range Air Pollution and Photochemistry Experiment (FRAPPE). The DC3 observations were made in May and June 2012 extending from the surface to 13 km over the central and eastern United States. FRAPPE observations were made in July and August 2014 from the surface to 7 km over Colorado. DC3 measurements reported here are focused over the Colorado Front Range and complement the FRAPPE observations. DC3 HFo altitude profiles are characterized by a decrease up to 6 km followed by an increase either back to boundary layer mixing ratio values or higher (a "C" shape). Organic acid measurements from both campaigns are interpreted with an emphasis on emission sources (both natural and anthropogenic) over Colorado and in situ photochemical production especially ozone precursors.

Primary structure of the human follistatin precursor and its genomic organization

International Nuclear Information System (INIS)

Shimasaki, Shunichi; Koga, Makoto; Esch, F.

1988-01-01

Follistatin is a single-chain gonadal protein that specifically inhibits follicle-stimulating hormone release. By use of the recently characterized porcine follistatin cDNA as a probe to screen a human testis cDNA library and a genomic library, the structure of the complete human follistatin precursor as well as its genomic organization have been determined. Three of eight cDNA clones that were sequenced predicted a precursor with 344 amino acids, whereas the remaining five cDNA clones encoded a 317 amino acid precursor, resulting from alternative splicing of the precursor mRNA. Mature follistatins contain four contiguous domains that are encoded by precisely separated exons; three of the domains are highly similar to each other, as well as to human epidermal growth factor and human pancreatic secretory trypsin inhibitor. The genomic organization of the human follistatin is similar to that of the human epidermal growth factor gene and thus supports the notion of exon shuffling during evolution

The weak acid resin process: a dustless conversion route for the synthesis of americium bearing-blanket precursors

International Nuclear Information System (INIS)

Picart, S.; Gauthe, A.; Parant, P.; Remy, E.; Jobelin, I.; Pomared, J.M.; Grangaud, P.; Dauby, J.; Delahaye, T.; Caisso, M.; Bataille, M.; Bayle, J.P.; Frost, C.; Delage, C.; Martin, C.L.; Ayral, E.

2016-01-01

Mixed uranium-americium oxides are one of the materials envisaged for Americium Bearing Blankets dedicated to transmutation in fast neutron reactors. Conversion and fabrication processes are currently developed to make those materials in the form of dense and homogeneous oxide ceramic pellets or dense granulates incorporating uranium and americium. Their development points out the need of a simplified and optimized process which could lower hazards linked to dust generation of highly contaminating and irradiating compounds and facilitate material transfer in remote handling operations. This reason motivated the development of innovative 'dustless' route such as the Weak Acid Resin route (WAR) which provides the oxide precursors in the form of sub-millimeter-sized microspheres with optimal flowability and limits dust generation during conversion and fabrication steps. This study is thus devoted to the synthesis of mixed uranium-americium oxide microspheres by the WAR process and to the characterization of such precursors. This work also deals with their application to the fabrication of dense or porous pellets and with their potential use as dense spherules to make Sphere-Pac fuel. (authors)

The weak acid resin process: a dustless conversion route for the synthesis of americium bearing-blanket precursors

Energy Technology Data Exchange (ETDEWEB)

Picart, S.; Gauthe, A.; Parant, P.; Remy, E.; Jobelin, I.; Pomared, J.M.; Grangaud, P.; Dauby, J.; Delahaye, T. [CEA, Centre de Marcoule, DEN/MAR/DRCP, F-30207 Bagnols-sur-Ceze (France); Caisso, M.; Bataille, M.; Bayle, J.P. [CEA, Centre de Marcoule, DEN/MAR/DTEC, F-30207 Bagnols-sur-Ceze (France); Frost, C. [CEA, Centre de Marcoule, DEN/MAR/DRCP, F-30207 Bagnols-sur-Ceze (France); Institut Europeen des Membranes, CNRS-ENSCM-UM, CC47, University of Montpellier, F-34095 Montpellier (France); Delage, C. [CEA, Centre de Cadarache, DEN/CAD/DEC, Saint-Paul-lez-Durance (France); Martin, C.L. [Univ. Grenoble Alpes, CNRS, SIMAP, F-38000 Grenoble (France); Ayral, E. [Institut Europeen des Membranes, CNRS-ENSCM-UM, CC47, University of Montpellier, F-34095 Montpellier (France)

2016-07-01

Mixed uranium-americium oxides are one of the materials envisaged for Americium Bearing Blankets dedicated to transmutation in fast neutron reactors. Conversion and fabrication processes are currently developed to make those materials in the form of dense and homogeneous oxide ceramic pellets or dense granulates incorporating uranium and americium. Their development points out the need of a simplified and optimized process which could lower hazards linked to dust generation of highly contaminating and irradiating compounds and facilitate material transfer in remote handling operations. This reason motivated the development of innovative 'dustless' route such as the Weak Acid Resin route (WAR) which provides the oxide precursors in the form of sub-millimeter-sized microspheres with optimal flowability and limits dust generation during conversion and fabrication steps. This study is thus devoted to the synthesis of mixed uranium-americium oxide microspheres by the WAR process and to the characterization of such precursors. This work also deals with their application to the fabrication of dense or porous pellets and with their potential use as dense spherules to make Sphere-Pac fuel. (authors)

Precursors of vertebrate peptide antibiotics dermaseptin b and adenoregulin have extensive sequence identities with precursors of opioid peptides dermorphin, dermenkephalin, and deltorphins.

Science.gov (United States)

Amiche, M; Ducancel, F; Mor, A; Boulain, J C; Menez, A; Nicolas, P

1994-07-08

The dermaseptins are a family of broad spectrum antimicrobial peptides, 27-34 amino acids long, involved in the defense of the naked skin of frogs against microbial invasion. They are the first vertebrate peptides to show lethal effects against the filamentous fungi responsible for severe opportunistic infections accompanying immunodeficiency syndrome and the use of immunosuppressive agents. A cDNA library was constructed from skin poly(A+) RNA of the arboreal frog Phyllomedusa bicolor and screened with an oligonucleotide probe complementary to the COOH terminus of dermaseptin b. Several clones contained a full-length DNA copy of a 443-nucleotide mRNA that encoded a 78-residue dermaseptin b precursor protein. The deduced precursor contained a putative signal sequence at the NH2 terminus, a 20-residue spacer sequence extremely rich (60%) in glutamic and aspartic acids, and a single copy of a dermaseptin b progenitor sequence at the COOH terminus. One clone contained a complete copy of adenoregulin, a 33-residue peptide reported to enhance the binding of agonists to the A1 adenosine receptor. The mRNAs encoding adenoregulin and dermaseptin b were very similar: 70 and 75% nucleotide identities between the 5'- and 3'-untranslated regions, respectively; 91% amino acid identity between the signal peptides; 82% identity between the acidic spacer sequences; and 38% identity between adenoregulin and dermaseptin b. Because adenoregulin and dermaseptin b have similar precursor designs and antimicrobial spectra, adenoregulin should be considered as a new member of the dermaseptin family and alternatively named dermaseptin b II. Preprodermaseptin b and preproadenoregulin have considerable sequence identities to the precursors encoding the opioid heptapeptides dermorphin, dermenkephalin, and deltorphins. This similarity extended into the 5'-untranslated regions of the mRNAs. These findings suggest that the genes encoding the four preproproteins are all members of the same family

Precipitation of plutonium oxalate from homogeneous solutions

International Nuclear Information System (INIS)

Rao, V.K.; Pius, I.C.; Subbarao, M.; Chinnusamy, A.; Natarajan, P.R.

1986-01-01

A method for the precipitation of plutonium(IV) oxalate from homogeneous solutions using diethyl oxalate is reported. The precipitate obtained is crystalline and easily filterable with yields in the range of 92-98% for precipitations involving a few mg to g quantities of plutonium. Decontamination factors for common impurities such as U(VI), Am(III) and Fe(III) were determined. TGA and chemical analysis of the compound indicate its composition as Pu(Csub(2)Osub(4))sub(2).6Hsub(2)O. Data are obtained on the solubility of the oxalate in nitric acid and in mixtures of nitric acid and oxalic acid of varying concentrations. Green PuOsub(2) obtained by calcination of the oxalate has specifications within the recommended values for trace foreign substances such as chlorine, fluorine, carbon and nitrogen. (author)

DISSOLUTION OF LANTHANUM FLUORIDE PRECIPITATES

Science.gov (United States)

Fries, B.A.

1959-11-10

A plutonium separatory ore concentration procedure involving the use of a fluoride type of carrier is presented. An improvement is given in the derivation step in the process for plutonium recovery by carrier precipitation of plutonium values from solution with a lanthanum fluoride carrier precipitate and subsequent derivation from the resulting plutonium bearing carrier precipitate of an aqueous acidic plutonium-containing solution. The carrier precipitate is contacted with a concentrated aqueous solution of potassium carbonate to effect dissolution therein of at least a part of the precipitate, including the plutonium values. Any remaining precipitate is separated from the resulting solution and dissolves in an aqueous solution containing at least 20% by weight of potassium carbonate. The reacting solutions are combined, and an alkali metal hydroxide added to a concentration of at least 2N to precipitate lanthanum hydroxide concomitantly carrying plutonium values.

Kinetics of cadmium hydroxide precipitation

International Nuclear Information System (INIS)

Patterson, J.W.; Marani, D.; Luo, B.; Swenson, P.

1987-01-01

This paper presents some preliminary results on the kinetics of Cd(OH)/sub 2/ precipitation, both in the absence and the presence of citric acid as an inhibiting agent. Batch and continuous stirred tank reactor (CSTR) precipitation studies are performed by mixing equal volumes of NaOH and Cd(NO/sub 3/)/sub 2/ solutions, in order to avoid localized supersaturation conditions. The rate of metal removal from the soluble phase is calculated from the mass balance for the CSTR precipitation tests. In addition, precipitation kinetics are studied in terms of nucleation and crystal growth rates, by means of a particle counter that allows a population balance analysis for the precipitation reactor at steady state conditions

Synthesis of aqueous suspensions of magnetic nanoparticles with the co-precipitation of iron ions in the presence of aspartic acid

Science.gov (United States)

Pušnik, Klementina; Goršak, Tanja; Drofenik, Miha; Makovec, Darko

2016-09-01

There is increasing demand for the production of large quantities of aqueous suspensions of magnetic iron-oxide nanoparticles. Amino acids are one possible type of inexpensive, nontoxic, and biocompatible molecules that can be used as the surfactants for the preparation of stable suspensions. This preparation can be conducted in a simple, one-step process based on the co-precipitation of Fe3+/Fe2+ ions in the presence of the amino acid. However, the presence of this amino acid changes the mechanism of the magnetic nanoparticles' formation. In this investigation we analyzed the influence of aspartic amino acid (Asp) on the formation of magnetic iron-oxide nanoparticles during the co-precipitation. The process of the nanoparticles' formation was followed using a combination of TEM, x-ray diffractometry, magnetic measurements, in-situ FT-IR spectroscopy, and chemical analysis, and compared with the formation of nanoparticles without the Asp. The Asp forms a coordination complex with the Fe3+ ions, which impedes the formation of the intermediate iron oxyhydroxide phase and suppresses the growth of the final magnetic iron-oxide nanoparticles. Slower reaction kinetics can lead to the formation of nonmagnetic secondary phases. The aspartic-acid-absorbed nanoparticles can be dispersed to form relatively concentrated aqueous suspensions displaying a good colloidal stability at an increased pH.

Pig epidermal growth factor precursor contains segments that are highly conserved among species

DEFF Research Database (Denmark)

Jørgensen, P E; Jensen, L.G.; Sørensen, B S

1998-01-01

segment with that of the human, the rat and the mouse EGF precursors, in order to identify highly conserved domains. The examined part of the precursor contains EGF itself and six so-called EGF-like modules. The overall amino acid identity among the four species is 64%. However, the amino acid identity...... differed from around 30% in some segments to around 70% in others. The highest amino acid identity, 71%, was observed for a 345-aa segment that contains three EGF-like modules and which is homologous to a part of the low-density lipoprotein receptor (LDL receptor). The amino acid identities are 64% for EGF...... itself, and 50-67% for the remaining three EGF-like modules. The segment of the LDL receptor that is homologous to a part of the EGF precursor is important for the function of the LDL receptor, and EGF-like modules seem to be involved in protein-protein interactions in a number of proteins. In conclusion...

Seasonal factors controlling mineral precipitation in the acid mine drainage at Donghae coal mine, Korea

International Nuclear Information System (INIS)

Kim, J.J.; Kim, S.J.

2004-01-01

Monitoring over a 12 month period in the Sanae creek flow in acid mine drainage, Donghae coal mine area, demonstrates that the concentrations of dissolved metals and sulphate are highest during autumn when water flow in the creek is at its lowest. The highest pH values of the stream were measured in April and May, whereas the lowest pH was recorded in October. The Fe concentration of stream water rapidly decreased downstream due to the precipitation of Fe oxyhydroxide and/or oxyhydroxysulfate phases in the stream. Mineral precipitates in the creek in the Donghae mine area show various colours such as brownish yellow (Munsell colour 9.5 YR hues), reddish brown (Munsell colour 3.5 YR hues) and white depending on seasons and distance from the pollution source in the creek. Such phenomena are attributed to the variation in pH and chemical composition of stream water caused by seasonal factors. The measured pH ranges in stream water of the brownish yellow, white and reddish brown precipitates are pH 3.2-4.5, 4.5-6.0 and 5.3-6.9, respectively

Atmospheric and precipitation chemistry over the North Atlantic Ocean: Shipboard results, April-May 1984

Science.gov (United States)

Church, T. M.; Tramontano, J. M.; Whelpdale, D. M.; Andreae, M. O.; Galloway, J. N.; Keene, W. C.; Knap, A. H.; Tokos, J.

1991-10-01

During a North Atlantic cruise from Dakar, Senegal, to Woods Hole, Massachusetts (April 14-May 11, 1984), crossing the area of 14°-48°N; 17°-70°W, we collected atmospheric aerosols (C, N, S species), gases (SO4, HNO3, dimethyl sulfide (DMS), synthetic organic chemicals), and precipitation (major inorganic/organic ions, trace metals). Air masses that had not contacted land for over 5 days had a composition close to that from the remote marine atmosphere. Oxidation of biogenic DMS to SO4= aerosol accounted for most nss-SO4= in these air masses. Air masses that had transected densely populated North America (in the westerlies) or the Mediterranean/North Africa ( in the easterlies) within 2-5 days of being sampled over the North Atlantic were enriched in acid precursor compounds and synthetic hydrocarbons relative to air that had spent longer over the North Atlantic. Strong acids and trace metals were also elevated in precipitation. Air masses that had transected regions of strong emissions within the preceding 2 days had concentrations of atmospheric pollutants approaching those typically found in continental air masses. More frequent storm tracks between the Icelandic low and the Bermuda high favored transport of North American emissions northeasterly, toward Europe. Trajectory analyses suggested that air masses sampled off the northwest African coast had passed over the Mediterranean. Composition of the aerosol and precipitation of these air masses was also indicative of continental emissions, including biomass and petroleum burning. Transport and deposition of continental emissions to the North Atlantic were significantly influencing surface atmospheric and oceanic chemistry of this region.

Synthesis of hydroxyapatite with the use of calcium carbonate as of the biological precursor; Sintese de hidroxiapatita com o uso de carbonato de calcio de origem biologica como precurssor

Energy Technology Data Exchange (ETDEWEB)

Aguilar, M.S.; Di Lello, B.C.; Queiroz, F.; Campos, N.C., E-mail: marilzasa@oi.com.br [Universidade Estacio de Sa (UESA), Rio de Janeiro, RJ (Brazil). Departamento de Engenharia; Campos, J.B. [Universidade do Estado do Rio de Janeiro (PPGEM/UERJ), RJ (Brazil). Programa de Pos-Graduacao em Engenharia Mecanica

2014-07-01

This work describes the synthesis of hydroxyapatite from calcium from biological materials such as shells carbonate. In the syntheses performed, the calcium carbonate of biological origin was used as the precursor and through a precipitation reaction with phosphoric acid, was converted into calcium hydroxide. Sequentially, the precipitate was aged, filtered, washed, dried and calcined, and then transformed into hydroxyapatite. The characterization of the powders was performed by X-DR (X-ray diffraction) and SEM (scanning electron microscopy). DR-X as determined hydroxyapatite calcium phosphate phase calcium. SEM revealed a morphology of finely divided particles. The method B.E.T. showed values of specific area and volume of micropores consistent with the literature. The results of the characterizations proved feasible to use for obtaining biological hydroxyapatite materials used in the reaction conditions.(author)

Relative importance and interactions of furan precursors in sterilised, vegetable-based food systems.

Science.gov (United States)

Palmers, Stijn; Grauwet, Tara; Buvé, Carolien; Vanratingen, Koen; Kebede, Biniam T; Goos, Peter; Hendrickx, Marc E; Van Loey, Ann

2016-01-01

Mitigation strategies aimed at an intervention in the reaction pathways for furan formation (e.g., by adjusting precursor concentrations) might offer an additional route for furan reduction in sterilised, vegetable-based foods, without adverse effects on other food safety or quality attributes. As a first step towards product reformulation, the aim of the present study was to determine the relative importance and interactions of possible furan precursors in these types of foods. Based on an I-optimal experimental design, potato purée (naturally low in furan precursors) was spiked with known amounts of sugars, ascorbic acid, olive oil and β-carotene, and subjected to a thermal sterilisation. Significant correlations were observed between furan concentrations after thermal treatment and starting concentrations of ascorbic acid and monosaccharides (i.e., fructose and glucose). Ascorbic acid had a clear furan-reducing effect as an antioxidant by protecting (polyunsaturated) fatty acids against oxidative degradation. Fructose and glucose were the main precursors, which can most probably be attributed to their high, but realistic, concentrations in the product. The contributions of fatty acids and β-carotene were strongly dependent on redox interactions with other food constituents. In the same potato purées, only low concentrations (0-2 ng g(-1) purée) of 2-methylfuran were detected, indicating that the direct importance of the spiked food constituents as a precursor for methylfuran formation was rather small. Based on the results of this study, reducing the amount of monosaccharides or adjusting the redox conditions of the matrix are suggested as two possible approaches for furan mitigation on the product side.

Membrane-associated precursor to poliovirus VPg identified by immunoprecipitation with antibodies directed against a synthetic heptapeptide

International Nuclear Information System (INIS)

Semelr, B.L.; Anderson, C.W.; Hanecak, R.; Dorner, L.F.; Wimmer, E.

1982-01-01

A synthetic heptapeptide corresponding to the C-terminal sequence of the poliovirus genome protein (VPg) has been linked to bovine serum albumin and used to raise antibodies in rabbits. These antibodies precipitate not only VPg but also at least two more virus-specific polypeptides. The smaller polypeptide, denoted P3-9 (12,000 daltons), has been mapped by Edman degradation and by fragmentation with cyanogen bromide and determined to be the N-terminal cleavage product of polypeptide P3-1b, a precursor to the RNA polymerase. P3-9 contains the sequence of the basic protein VPg (22 amino acids) at its C terminus. As predicted by the known RNA sequence of poliovirus, P3-9 also contains a hydrophobic region of 22 amino acids preceding VPg, an observation suggesting that P3-9 may be membrane-associated. This was confirmed by fractionation of infected cells in the presence or absence of detergent. We speculate that P3-9 may be the donor of VPg to RNA chains in the membrane-bound RNA replication complex

Crosslinkers of Different Types in Precipitation Polymerization of Acrylic Acid

Directory of Open Access Journals (Sweden)

H. Eshaghi

2013-01-01

Full Text Available Crosslinked poly(acrylic acids were prepared using two types of crosslinker by precipitation polymerization method in a binary organic solvent. N,N’-methylenebisacrylamide (MBA and polyethylene glycol dimethacrylate (PEGDMA-330 were used as low-molecular weight and long-chain crosslinkers, respectively. The effect of various types of crosslinkers on polymer characteristics (i.e., gel content, equilibrium swelling, glass transition temperature, and rheological properties was investigated. Maximum amount of viscosity was obtained by using long-chain crosslinker. The Flory-Rehner equation and rubber elasticity theory were used to discuss the network structure of polymer. It was observed that, the glass transition temperature (Tg of the synthesized polymer containing PEGDMA-330 is higher than that of polymer containing MBA. Apparent and rotational viscosity were used to determine the optimal crosslinker type. In addition, the consistencycoefficient (m and flow behavior index (n parameter of Ostwald equation were investigated as well.

An Optimized Trichloroacetic Acid/Acetone Precipitation Method for Two-Dimensional Gel Electrophoresis Analysis of Qinchuan Cattle Longissimus Dorsi Muscle Containing High Proportion of Marbling.

Science.gov (United States)

Hao, Ruijie; Adoligbe, Camus; Jiang, Bijie; Zhao, Xianlin; Gui, Linsheng; Qu, Kaixing; Wu, Sen; Zan, Linsen

2015-01-01

Longissimus dorsi muscle (LD) proteomics provides a novel opportunity to reveal the molecular mechanism behind intramuscular fat deposition. Unfortunately, the vast amounts of lipids and nucleic acids in this tissue hampered LD proteomics analysis. Trichloroacetic acid (TCA)/acetone precipitation is a widely used method to remove contaminants from protein samples. However, the high speed centrifugation employed in this method produces hard precipitates, which restrict contaminant elimination and protein re-dissolution. To address the problem, the centrifugation precipitates were first grinded with a glass tissue grinder and then washed with 90% acetone (TCA/acetone-G-W) in the present study. According to our result, the treatment for solid precipitate facilitated non-protein contaminant removal and protein re-dissolution, ultimately improving two-dimensional gel electrophoresis (2-DE) analysis. Additionally, we also evaluated the effect of sample drying on 2-DE profile as well as protein yield. It was found that 30 min air-drying did not result in significant protein loss, but reduced horizontal streaking and smearing on 2-DE gel compared to 10 min. In summary, we developed an optimized TCA/acetone precipitation method for protein extraction of LD, in which the modifications improved the effectiveness of TCA/acetone method.

Hydrolysis of glyoxal in water-restricted environments: formation of organic aerosol precursors through formic acid catalysis.

Science.gov (United States)

Hazra, Montu K; Francisco, Joseph S; Sinha, Amitabha

2014-06-12

The hydrolysis of glyoxal involving one to three water molecules and also in the presence of a water molecule and formic acid has been investigated. Our results show that glyoxal-diol is the major product of the hydrolysis and that formic acid, through its ability to facilitate intermolecular hydrogen atom transfer, is considerably more efficient than water as a catalyst in the hydrolysis process. Additionally, once the glyoxal-diol is formed, the barrier for further hydrolysis to form the glyoxal-tetrol is effectively reduced to zero in the presence of a single water and formic acid molecule. There are two important implications arising from these findings. First, the results suggest that under the catalytic influence of formic acid, glyoxal hydrolysis can impact the growth of atmospheric aerosols. As a result of enhanced hydrogen bonding, mediated through their polar OH functional groups, the diol and tetrol products are expected to have significantly lower vapor pressure than the parent glyoxal molecule; hence they can more readily partition into the particle phase and contribute to the growth of secondary organic aerosols. In addition, our findings provide insight into how glyoxal-diol and glyoxal-tetrol might be formed under atmospheric conditions associated with water-restricted environments and strongly suggest that the formation of these precursors for secondary organic aerosol growth is not likely restricted solely to the bulk aqueous phase as is currently assumed.

Elucidation of the biosynthesis of eicosapentaenoic acid in the microalga Porphyridium cruentum. II. Studies with radiolabeled precursors

International Nuclear Information System (INIS)

Khozin, I.; Adlerstein, D.; Bigongo, C.; Heimer, Y.M.; Cohen, Z.

1997-01-01

In the course of the study of the biosynthesis of the fatty acid eicosapentaenoic acid (EPA) in the microalga Porphyridium cruentum, cells were pulse-labeled with various radiolabeled fatty acid precursors. Our data show that the major end products of the biosynthesis are EPA-containing galactolipids of a eukaryotic and prokaryotic nature. The prokaryotic molecular species contain EPA and arachidonic acid at the sn-1 position and C16 fatty acids, mainly 16:0, at the sn-2 positions, whereas in the eukaryotic species both positions are occupied by EPA or arachidonic acid. However, we suggest that both the eukaryotic and prokaryotic molecular species are formed in two pathways, omega 6 and omega 3, which involve cytoplasmic and chloroplastic lipids. In the omega 6 pathway, cytoplasmic 18:2-phosphatidylcholine (PC) is converted to 20:4 omega 6-PC by a sequence that includes a delta 6 desaturase, an elongation step, and a delta 5 desaturase. In the minor omega 3 pathway, 18:2-PC is presumably desaturated to 18:3 omega 3, which is sequentially converted by the enzymatic sequence of the omega 6 pathway to 20:5 omega 3-PC. The products of both pathways are exported, as their diacylglycerol moieties, to the chloroplast to be galactosylated into their respective monogalactosyldiacylglycerol molecular species. The 20:4 omega 6 in both eukaryotic and prokaryotic monogalactosyldiacylglycerol can be further desaturated to EPA by a chloroplastic delta 17 (omega 3) desaturase

The role of phosphate additive in stabilization of sulphuric-acid-based vanadium(V) electrolyte for all-vanadium redox-flow batteries

Science.gov (United States)

Roznyatovskaya, Nataliya V.; Roznyatovsky, Vitaly A.; Höhne, Carl-Christoph; Fühl, Matthias; Gerber, Tobias; Küttinger, Michael; Noack, Jens; Fischer, Peter; Pinkwart, Karsten; Tübke, Jens

2017-09-01

Catholyte in all-vanadium redox-flow battery (VRFB) which consists of vanadium salts dissolved in sulphuric acid is known to be stabilized by phosphoric acid to slow down the thermal aging at temperatures higher than 40 °C. To reveal the role of phosphoric acid, the thermally-induced aggregation is investigated using variable-temperature 51V, 31P, 17O, 1H nuclear magnetic resonance (NMR) spectroscopy and dynamic light scattering (DLS). The results indicate that the thermal stabilization of vanadium(V) electrolyte is attained by the involvement of monomeric and dimeric vanadium(V) species in the reaction with phosphoric acid which is concurrent to the formation of neutral hydroxo-aqua vanadium(V) precipitation precursor. The dimers are stabilized by counter ions due to association reaction or if such stabilization is not possible, precipitation of vanadium pentoxide is favored. The evolution of particles size distributions at 50 °C in electrolyte samples containing 1.6 M vanadium and 4.0 M total sulphate and the pathways of precipitate formation are discussed. The optimal total phosphate concentration is found to be of 0.15 M. However, the induction time is assumed to be dependent not only on the total phosphate concentrations, but also on the ratio of total vanadium(V) to sulphate concentrations.

Organic influences on inorganic patterns of diffusion-controlled precipitation in gels

Science.gov (United States)

Barge, Laura M.; Nealson, Kenneth H.; Petruska, John

2010-06-01

The well-known AgNO 3/K 2CrO 4 reaction-diffusion system produces periodic bands of silver chromate precipitate in gelatin, but only randomly oriented crystals in agarose gel. We show that comparable bands can be produced in agarose gel by adding small amounts of simple organic acids (e.g., acetic acid, N-acetyl glycine, and N-acetyl alanine) that suppress crystal growth and promote formation of rounded particles of precipitate. These results indicate that α-carboxyl groups of amino acids or short peptides in gelatin under mildly acidic conditions can induce periodic band patterns in diffusion-controlled silver chromate precipitates.

A perspective of stepwise utilisation of Bayer red mud: Step two—Extracting and recovering Ti from Ti-enriched tailing with acid leaching and precipitate flotation

International Nuclear Information System (INIS)

Huang, Yanfang; Chai, Wencui; Han, Guihong; Wang, Wenjuan; Yang, Shuzhen; Liu, Jiongtian

2016-01-01

Highlights: • An integrated process for the stepwise disposal of red mud was proposed. • Extracting and recovering Ti from Ti-enriched tailing was the second step. • The factors influencing acid leaching and precipitate flotation were examined. • The extracting of metals in concentrated H 2 SO 4 was controlled by diffusion reactions. • [Hbet][Tf 2 N] was an effective precipitating reagent with its coordination mechanism. - Abstract: The extraction and recovery of Ti from Ti-enriched tailing with acid leaching and precipitate flotation, as one of the critical steps, was proposed for the stepwise utilization of red mud. The factors influencing acid leaching and precipitate flotation were examined by factorial design. The leaching thermodynamics, kinetics of Ti 4+ , Al 3+ and Fe 3+ , and the mechanism of selectively Fe 3+ removal using [Hbet][Tf 2 N] as precipitating reagent were discussed. The extracting of Ti 4+ , Al 3+ and Fe 3+ in concentrated H 2 SO 4 is controlled by diffusion reactions, depending mainly upon leaching time and temperature. The maximum extracting efficiency of Ti 4+ is approximately 92.3%, whereas Al 3+ and Fe 3+ leaching are respectively 75.8% and 84.2%. [Hbet][Tf 2 N], as a precipitating reagent, operates through a coordination mechanism in flotation. The pH value is the key factor influencing the flotation recovery of Ti 4+ , whereas the dosage of precipitating reagent is that for Al 3+ recovery. The maximum flotation recovery of Ti 4+ is 92.7%, whereas the maximum Al 3+ recovery is 93.5%. The total recovery rate for extracting and recovering titanium is 85.5%. The liquor with Ti 4+ of 15.5 g/L, Al 3+ of 30.4 g/L and Fe 3+ of 0.48 g/L was obtained for the following hydrolysis step in the integrated process for red mud utilisation.

Cumulus expansion, nuclear maturation and connexin 43, cyclooxygenase-2 and FSH receptor mRNA expression in equine cumulus-oocyte complexes cultured in vitro in the presence of FSH and precursors for hyaluronic acid synthesis

Directory of Open Access Journals (Sweden)

Aiudi Giulio

2004-06-01

Full Text Available Abstract The aim of this study was to investigate cumulus expansion, nuclear maturation and expression of connexin 43, cyclooxygenase-2 and FSH receptor transcripts in equine cumuli oophori during in vivo and in vitro maturation in the presence of equine FSH (eFSH and precursors for hyaluronic acid synthesis. Equine cumulus-oocyte complexes (COC were cultured in a control defined medium supplemented with eFSH (0 to 5 micrograms/ml, Fetal Calf Serum (FCS, precursors for hyaluronic acid synthesis or glutamine according to the experiments. After in vitro maturation, the cumulus expansion rate was increased with 1 microgram/ml eFSH, and was the highest with 20% FCS. It was not influenced by precursors for hyaluronic acid synthesis or glutamine. The expression of transcripts related to cumulus expansion was analyzed in equine cumulus cells before maturation, and after in vivo and in vitro maturation, by using reverse transcription-polymerase chain reaction (RT-PCR with specific primers. Connexin 43, cyclooxygenase-2 (COX-2 and FSH receptor (FSHr mRNA were detected in equine cumulus cells before and after maturation. Their level did not vary during in vivo or in vitro maturation and was influenced neither by FSH nor by precursors for hyaluronic acid synthesis. Results indicate that previously reported regulation of connexin 43 and COX-2 proteins during equine COC maturation may involve post-transcriptional mechanisms.

Removal of palladium precipitate from a simulated high-level radioactive liquid waste by reduction by ascorbic acid

International Nuclear Information System (INIS)

Kim, Eung Ho; Yoo, Jae Hyung; Choi, Cheong Song

1998-01-01

A study of the selective removal of Palladium from a simulated solution of high-level radioactive liquid waste (HLLW) was carried out. The simulated solution contained 7 representative elements (Pd 2+ , Cs + , Sr 2+ , Fe 3+ , MoO 2 2+ , Ru 4+ , and Nd 3+ ) typical of HLLW, ascorbic acid was added to the solution at room temperature. Pd 2+ in the simulated solution was easily reduced to Pd metal by the ascorbic acid and then the metal precipitate could be removed from the solution, whereas other elements remained mainly in solution. When the resulting Pd metal was left in solution, it was reoxidized to Pb 2+ ion and redissolved in a nitric acid medium. The oxidation rate of Pd 2+ depended on the presence of a transition metal such as ferric ion, and was also in proportion to the concentration of nitric acid and in inverse proportion to the concentration of ascrobic acid. (orig.)

Secondary precipitation in an Al-Mg-Si-Cu alloy

International Nuclear Information System (INIS)

Buha, J.; Lumley, R.N.; Crosky, A.G.; Hono, K.

2007-01-01

Interruption of a conventional T6 heat treatment at 177 deg. C for the Al-Mg-Si-Cu alloy 6061 after a short period of time (20 min), by inserting a dwell period at a lower temperature (e.g. 65 deg. C), promotes secondary precipitation of Guinier-Preston (GP) zones. As a consequence, a much greater number of precursors to the β'' precipitates are produced so that a finer and denser dispersion of this phase is formed when T6 ageing is resumed. This change in microstructure causes significant and simultaneous improvements in tensile properties and fracture toughness. Secondary precipitation of GP zones occurs through a gradual evolution of a large number of Mg-Si(-Cu)-vacancy co-clusters formed during the initial ageing at 177 deg. C. The precise mechanism of secondary precipitation has been revealed by three-dimensional atom probe microscopy supplemented by transmission electron microscopy and differential scanning calorimetry

Thermogravimetric evaluation of the suitability of precursors for MOCVD

International Nuclear Information System (INIS)

Kunte, G V; Shivashankar, S A; Umarji, A M

2008-01-01

A method based on the Langmuir equation for the estimation of vapour pressure and enthalpy of sublimation of subliming compounds is described. The variable temperature thermogravimetric/differential thermogravimetric (TG/DTG) curve of benzoic acid is used to arrive at the instrument parameters. Employing these parameters, the vapour pressure–temperature curves are derived for salicylic acid and camphor from their TG/DTG curves. The values match well with vapour pressure data in the literature, obtained by effusion methods. By employing the Clausius–Clapeyron equation, the enthalpy of sublimation could be calculated. Extending the method further, two precursors for metal-organic chemical vapour deposition (MOCVD) of titanium oxide bis-isopropyl bis tert-butyl 2-oxobutanoato titanium, Ti(O i Pr) 2 (tbob) 2 , and bis-oxo-bis-tertbutyl 2-oxobutanoato titanium, [TiO(tbob) 2 ] 2 , have been evaluated. The complex Ti(O i Pr) 2 (tbob) 2 is found to be a more suitable precursor. This approach can be helpful in quickly screening for the suitability of a compound as a CVD precursor

Formation of TiC/Al{sub 2}O{sub 3} composites from metal-polymer-precursors

Energy Technology Data Exchange (ETDEWEB)

Jost, H.; Braun, M.; Staedler, C. [Technische Univ. Berlin (Germany). Inst. fuer Nichtmetallische Werkstoffe

2002-07-01

A new synthesis route for TiC/Al{sub 2}O{sub 3} materials was developed starting from a mixed metal-polymer precursor. The Precursor was prepared from aluminium nitrate, titantetrachloride and polymethacrylic acid dissolved in a solvent in order to achieve a high homogeneity of the precursor reactants. (orig.)

High-performance oxygen reduction catalysts in both alkaline and acidic fuel cells based on pre-treating carbon material and iron precursor

Energy Technology Data Exchange (ETDEWEB)

Song, Ping; Barkholtz, Heather M.; Wang, Ying; Xu, Weilin; Liu, Dijia; Zhuang, Lin

2017-12-01

We demonstrate a new and simple method for pre-treating the carbon material and iron precursor to prepare oxygen reduction reaction (ORR) catalysts, which can produce super-high performance and stability in alkaline solution, with high performance in acid solution. This strategy using cheap materials is simply controllable. Moreover, it has achieved smaller uniform nanoparticles to exhibit high stability, and the synergetic effect of Fe and N offered much higher performance in ORR than commercial Pt/C, with high maximum power density in alkaline and acid fuel cell test. So it can make this kind of catalysts be the most promising alternatives of Pt-based catalysts with best performance/price.

Effective reduction in the nanoparticle sizes of NiO obtained via the pyrolysis of nickel malonate precursor modified using oleylamine surfactant

Energy Technology Data Exchange (ETDEWEB)

Lontio Fomekong, Roussin, E-mail: lonforou@yahoo.fr [Chemistry Department, Higher Teacher Training College, University of Yaoundé I, B.P. 47, Yaoundé (Cameroon); Institut de la Matière Condensée et des Nanosciences, Université Catholique de Louvain, Croix du Sud 1, 1348 Louvain-La-Neuve (Belgium); Ngolui Lambi, John; Ebede, Guy Roland [Chemistry Department, Higher Teacher Training College, University of Yaoundé I, B.P. 47, Yaoundé (Cameroon); Kenfack Tsobnang, Patrice [Chemistry Department, University of Dschang, PO Box 96, Dschang (Cameroon); Tedjieukeng Kamta, Hypolite Mathias; Ngnintedem Yonti, Cedrik [Chemistry Department, Higher Teacher Training College, University of Yaoundé I, B.P. 47, Yaoundé (Cameroon); Delcorte, Arnaud [Institut de la Matière Condensée et des Nanosciences, Université Catholique de Louvain, Croix du Sud 1, 1348 Louvain-La-Neuve (Belgium)

2016-09-15

Nickel oxide nanoparticles were synthesized via thermal decomposition of two precursors, the first, a simple nickel malonate and the second, a nickel malonate modified by oleylamine, a surfactant, both having been synthesized by precipitation. While FTIR, TGA and ToF-SIMS were used to characterize the two precursors and to show the presence of oleylamine in the modified precursor, XRD, SEM, TEM and BET were employed to investigate the structure, the morphology and the specific surface area of the decomposition products obtained after pyrolysis. The results showed that the modification of nickel malonate by oleylamine was effective. The XRD results, which showed a cubic structure for the NiO obtained, suggest with SEM an important particle size reduction (at least 54%) when oleylamine was used to modify the nickel malonate precursor. The SEM images also showed a well-defined spherical nanoparticle morphology in both cases, not affected by the presence of oleylamine. The TEM also confirmed the reduction of particle size and their spherical nature but at the same time showed that, in the presence of oleylamine, there was no agglomeration resulting in a more uniform particle size distribution. The specific surface area of the NiO obtained by the oleylamine-modified precursor was 4.7 times larger than that obtained with the regular precursor. This again confirms the particle size reduction. - Highlights: • Nickel malonate precursor has been synthesized by precipitation method. • This precursor was successfully modified by a surfactant (oleylamine). • NiO was identified as the decomposition products of the previous precursors. • Oleylamine has provoked around 54% of particle size reduction of the NiO.

The usability of ark clam shell (Anadara granosa) as calcium precursor to produce hydroxyapatite nanoparticle via wet chemical precipitate method in various sintering temperature.

Science.gov (United States)

Khiri, Mohammad Zulhasif Ahmad; Matori, Khamirul Amin; Zainuddin, Norhazlin; Abdullah, Che Azurahanim Che; Alassan, Zarifah Nadakkavil; Baharuddin, Nur Fadilah; Zaid, Mohd Hafiz Mohd

2016-01-01

This paper reported the uses of ark clam shell calcium precursor in order to form hydroxyapatite (HA) via the wet chemical precipitation method. The main objective of this research is to acquire better understanding regarding the effect of sintering temperature in the fabrication of HA. Throughout experiment, the ratio of Ca:P were constantly controlled, between 1.67 and 2.00. The formation of HA at these ratio was confirmed by means of energy-dispersive X-ray spectroscopy analysis. In addition, the effect of sintering temperature on the formation of HA was observed using X-ray diffraction analysis, while the structural and morphology was determined by means of field emission scanning electron microscopy. The formation of HA nanoparticle was recorded (~35-69 nm) in the form of as-synthesize HA powder. The bonding compound appeared in the formation of HA was carried out using Fourier transform infrared spectroscopy such as biomaterials that are expected to find potential applications in orthopedic and biomedical industries .

Behaviour of the pH adjustment, Ion exchange and concentrate precipitation stages in the acid leaching of uranium phosphate ores

International Nuclear Information System (INIS)

Estrada Aguilar, J.; Uriarte Hueda, A.

1962-01-01

The uranium recovery from acid leach solutions of uranium-phosphate ores has been studied. Relations have been found between the solution characteristics and the results obtained at different stages of the process. The following data can thus be predicted: solids to remove and uranium recovery in the pH adjustment stage, uranium capacity of the resin, more suitable eluating agent, elution velocity and uranium concentration in the eluate in the ion exchange stage, and composition of the concentrate produced by direct precipitation of the eluate in the concentrate precipitation stage. (Author) 8 refs

Application of citric acid in acid stimulation treatments

Energy Technology Data Exchange (ETDEWEB)

Alkhaldi, M.H.; Sarma, H.K. [Adelaide Univ., Adelaide (Australia); Nasr-el-Din, H.A. [Texas A and M Univ., College Station, TX (United States)

2009-07-01

A rotating disk apparatus was used to investigate mass transfer during the reaction of citric acid with calcite. The study evaluated the effects of initial acid concentrations, temperature, and disk rotational speed on the effective diffusion coefficient of citric acid. The diffusion coefficient was calculated at 25, 40, and 50 degrees C using various citric acid concentrations. The study indicated that the coefficient was a function of the interactions between calcium citrate precipitation and counter calcium ions. At high acid concentrations, the effects of calcium citrate precipitation and counter calcium ions were significant. The calculated citric acid diffusion coefficients were not comparable with measured effective diffusion coefficients using the rotating disk. At lower initial citric acid concentrations, the effects of both calcium citrate precipitation and counter calcium ions on citric acid diffusivity were minimal. It was concluded that temperature effects on the diffusion coefficient followed Arrhenius law. Activation energy was equal to 37.9 kJ/mol. 34 refs., 4 tabs., 13 figs.

Boronic Acid functionalized core-shell polymer nanoparticles prepared by distillation precipitation polymerization for glycopeptide enrichment.

Science.gov (United States)

Qu, Yanyan; Liu, Jianxi; Yang, Kaiguang; Liang, Zhen; Zhang, Lihua; Zhang, Yukui

2012-07-16

The boronic acid-functionalized core-shell polymer nanoparticles, poly(N,N-methylenebisacrylamide-co-methacrylic acid)@4-vinylphenylboronic acid (poly(MBA-co-MAA)@VPBA), were successfully synthesized for enriching glycosylated peptides. Such nanoparticles were composed of a hydrophilic polymer core prepared by distillation precipitation polymerization (DPP) and a boronic acid-functionalized shell designed for capturing glycopeptides. Owing to the relatively large amount of residual vinyl groups introduced by DPP on the core surface, the VPBA monomer was coated with high efficiency, working as the shell. Moreover, the overall polymerization route, especially the use of DPP, made the synthesis of nanoparticles facile and time-saving. With the poly(MBA-co-MAA)@VPBA nanoparticles, 18 glycopeptides from horseradish peroxidase (HRP) digest were captured and identified by MALDI-TOF mass spectrometric analysis, relative to eight glycopeptides enriched by using commercially available meta-aminophenylboronic acid agarose under the same conditions. When the concentration of the HRP digest was decreased to as low as 5 nmol, glycopeptides could still be selectively isolated by the prepared nanoparticles. Our results demonstrated that the synthetic poly(MBA-co-MAA)@VPBA nanoparticles might be a promising selective enrichment material for glycoproteome analysis. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The NAD+ precursor nicotinic acid improves genomic integrity in human peripheral blood mononuclear cells after X-irradiation.

Science.gov (United States)

Weidele, Kathrin; Beneke, Sascha; Bürkle, Alexander

2017-04-01

NAD + is an essential cofactor for enzymes catalyzing redox-reactions as well as an electron carrier in energy metabolism. Aside from this, NAD + consuming enzymes like poly(ADP-ribose) polymerases and sirtuins are important regulators involved in chromatin-restructuring processes during repair and epigenetics/transcriptional adaption. In order to replenish cellular NAD + levels after cleavage, synthesis starts from precursors such as nicotinamide, nicotinamide riboside or nicotinic acid to match the need for this essential molecule. In the present study, we investigated the impact of supplementation with nicotinic acid on resting and proliferating human mononuclear blood cells with a focus on DNA damage and repair processes. We observed that nicotinic acid supplementation increased NAD + levels as well as DNA repair efficiency and enhanced genomic stability evaluated by micronucleus test after x-ray treatment. Interestingly, resting cells displayed lower basal levels of DNA breaks compared to proliferating cells, but break-induction rates were identical. Despite similar levels of p53 protein upregulation after irradiation, higher NAD + concentrations led to reduced acetylation of this protein, suggesting enhanced SIRT1 activity. Our data reveal that even in normal primary human cells cellular NAD + levels may be limiting under conditions of genotoxic stress and that boosting the NAD + system with nicotinic acid can improve genomic stability. Copyright © 2017 Elsevier B.V. All rights reserved.

Study of Gel Growth Cobalt (II Oxalate Crystals as Precursor of Co3O4 Nano Particles

Directory of Open Access Journals (Sweden)

Yuniar Ponco Prananto

2013-03-01

Full Text Available Crystal growth of cobalt (II oxalate in silica gel at room temperature as precursor of Co3O4 nano particles has been studied. Specifically, this project is focusing on the use of two different reaction tube types toward crystallization of cobalt (II oxalate in gel. The gel was prepared at pH 5 by reacting sodium metasilicate solution with dilute nitric acid (for U-tube and oxalic acid (for straight tube, with gelling time of 4 days and crystal growth time of 8 (for straight tube and 12 (for U-tube weeks. Result shows that pink crystalline powder was directly formed using straight tube method. The use of different solvents in straight tube method affects crystallization and could delay direct precipitation of the product. In contrast, bigger and better shape of red block crystal was yielded from U-tube method; however, longer growth time was needed. FTIR studies suggest that both growth method produces identical compound of hydrated cobalt (II oxalate. © 2013 BCREC UNDIP. All rights reservedReceived: 25th October 2012; Revised: 30th November 2012; Accepted: 5th December 2012[How to Cite: Y.P. Prananto, M.M. Khunur, D.T. Wahyuni, R.A. Shobirin, Y.R. Nata, E. Riskah, (2013. Study of Gel Growth Cobalt (II Oxalate Crystals as Precursor of Co3O4 Nano Particles. Bulletin of Chemical Reaction Engineering & Catalysis, 7 (3: 198-204. (doi:10.9767/bcrec.7.3.4066.198-204][Permalink/DOI: http://dx.doi.org/10.9767/bcrec.7.3.4066.198-204 ] View in  |

Hydroxide precursors to produce nanometric YCrO3: Characterization and conductivity analysis

International Nuclear Information System (INIS)

Durán, A.; Meza F, C.; Arizaga, Gregorio Guadalupe Carbajal

2012-01-01

Highlights: ► Y/Cr mixed hydroxide was precipitated with gaseous ammonia. ► The hydroxide treated at 1373 K formed YCrO 3 crystals with 20 nm diameter. ► Electrical properties were different than those found in other methods of synthesis. ► E act suggests small-polarons as conduction mechanisms. -- Abstract: A precursor to produce perovskite-type YCrO 3 was precipitated by bubbling gaseous ammonia into an yttrium/chromium salts solution. X-ray diffraction showed that the as-prepared powders were amorphous. Thermal treatment between 1273 and 1373 K, leads to formation of polycrystalline YCrO 3 with crystal sizes around 20 nm. High resolution X-ray photoelectron spectra showed uniform chemical environment for yttrium and chromium in the amorphous hydroxide and crystalline YCrO 3 . Shifts between Y 3d 5/2 and Cr 2p 3/2 binding energy suggest redistribution or charge transfer between yttrium and chromium ions in the YCrO 3 structure. The electrical properties of YCrO 3 , whose precursors were precipitated with gaseous ammonia are different than those prepared by combustion synthesis. Electrical conductivity presents a sudden increase at ∼473 K, which is associated to the grain size and morphology of the crystallites. The redistribution of charge between Y(III) and Cr(III) is thermally activated by the hopping of small-polarons, which are characterized by the Arrhenius law as the conductive mechanism.

A perspective of stepwise utilisation of Bayer red mud: Step two—Extracting and recovering Ti from Ti-enriched tailing with acid leaching and precipitate flotation

Energy Technology Data Exchange (ETDEWEB)

Huang, Yanfang; Chai, Wencui; Han, Guihong, E-mail: guihong-han@hotmail.com; Wang, Wenjuan; Yang, Shuzhen; Liu, Jiongtian

2016-04-15

Highlights: • An integrated process for the stepwise disposal of red mud was proposed. • Extracting and recovering Ti from Ti-enriched tailing was the second step. • The factors influencing acid leaching and precipitate flotation were examined. • The extracting of metals in concentrated H{sub 2}SO{sub 4} was controlled by diffusion reactions. • [Hbet][Tf{sub 2}N] was an effective precipitating reagent with its coordination mechanism. - Abstract: The extraction and recovery of Ti from Ti-enriched tailing with acid leaching and precipitate flotation, as one of the critical steps, was proposed for the stepwise utilization of red mud. The factors influencing acid leaching and precipitate flotation were examined by factorial design. The leaching thermodynamics, kinetics of Ti{sup 4+}, Al{sup 3+} and Fe{sup 3+}, and the mechanism of selectively Fe{sup 3+} removal using [Hbet][Tf{sub 2}N] as precipitating reagent were discussed. The extracting of Ti{sup 4+}, Al{sup 3+} and Fe{sup 3+} in concentrated H{sub 2}SO{sub 4} is controlled by diffusion reactions, depending mainly upon leaching time and temperature. The maximum extracting efficiency of Ti{sup 4+} is approximately 92.3%, whereas Al{sup 3+} and Fe{sup 3+} leaching are respectively 75.8% and 84.2%. [Hbet][Tf{sub 2}N], as a precipitating reagent, operates through a coordination mechanism in flotation. The pH value is the key factor influencing the flotation recovery of Ti{sup 4+}, whereas the dosage of precipitating reagent is that for Al{sup 3+} recovery. The maximum flotation recovery of Ti{sup 4+} is 92.7%, whereas the maximum Al{sup 3+} recovery is 93.5%. The total recovery rate for extracting and recovering titanium is 85.5%. The liquor with Ti{sup 4+} of 15.5 g/L, Al{sup 3+} of 30.4 g/L and Fe{sup 3+} of 0.48 g/L was obtained for the following hydrolysis step in the integrated process for red mud utilisation.

Antisolvent Precipitation for the Synthesis of Monodisperse Mesoporous Niobium Oxide Spheres as Highly Effective Solid Acid Catalysts

KAUST Repository

Li, Cheng Chao; Dou, Jian; Chen, Luwei; Lin, Jianyi; Zeng, Hua Chun

2012-01-01

We have developed a low-cost reaction protocol to synthesize mesoporous Nb 2O 5-based solid acid catalysts with external shape control. In the synthesis, monodisperse glycolated niobium oxide spheres (GNOS) were prepared by means of a simple antisolvent precipitation approach and subsequently converted to mesoporous niobium oxide spheres (MNOS) with a large surface area of 312m 2g -1 by means of the hydrothermal treatment. The antisolvent acetone used to obtain GNOS was recovered through distillation at high purity. The obtained mesoporous MNOS were functionalized further with sulfate anions at different temperatures or incorporated with tungstophosphoric acid to obtain recyclable solid acid catalysts. These MNOS-based catalysts showed excellent performance in a wide range of acid-catalyzed reactions, such as Friedel-Crafts alkylation, esterification, and hydrolysis of acetates. As they are monodisperse spheres with diameters in the submicrometer range, the catalysts can be easily separated and reused. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Antisolvent Precipitation for the Synthesis of Monodisperse Mesoporous Niobium Oxide Spheres as Highly Effective Solid Acid Catalysts

KAUST Repository

Li, Cheng Chao

2012-03-20

We have developed a low-cost reaction protocol to synthesize mesoporous Nb 2O 5-based solid acid catalysts with external shape control. In the synthesis, monodisperse glycolated niobium oxide spheres (GNOS) were prepared by means of a simple antisolvent precipitation approach and subsequently converted to mesoporous niobium oxide spheres (MNOS) with a large surface area of 312m 2g -1 by means of the hydrothermal treatment. The antisolvent acetone used to obtain GNOS was recovered through distillation at high purity. The obtained mesoporous MNOS were functionalized further with sulfate anions at different temperatures or incorporated with tungstophosphoric acid to obtain recyclable solid acid catalysts. These MNOS-based catalysts showed excellent performance in a wide range of acid-catalyzed reactions, such as Friedel-Crafts alkylation, esterification, and hydrolysis of acetates. As they are monodisperse spheres with diameters in the submicrometer range, the catalysts can be easily separated and reused. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Influence of chemical composition of precipitation on migration of radioactive caesium in natural soils

International Nuclear Information System (INIS)

Thørring, H.; Skuterud, L.; Steinnes, E.

2014-01-01

The aim of the present work was to study the impact of the chemical composition of precipitation on radiocaesium mobility in natural soil. This was done through column studies. Three types of precipitation regimes were studied, representing a natural range found in Norway: Acidic precipitation (southernmost part of the country); precipitation rich in marine cations (highly oceanic coastal areas); and low concentrations of sea salts (slightly continental inland areas). After 50 weeks and a total precipitation supply of ∼10 000 L m −2 per column, results indicate that acidic precipitation increased the mobility of 134 Cs added during the experiment. However, depth distribution of already present Chernobyl fallout 137 Cs was not significantly affected by the chemical composition of precipitation. - Highlights: • Mobility of freshly added Cs-134 was higher in soil receiving acidic precipitation. • Depth penetration of Cs-134 was higher in soil profiles with a thicker humus layer. • Depth distribution of Chernobyl Cs-137 was not affected by precipitation type

Prediction and mastering of wine acidity and tartaric precipitations: the Mextar® software tool

Directory of Open Access Journals (Sweden)

Audrey Devatine

2002-06-01

The article describes the theoretical background upon which MEXTAR® has been developed and details the computation procedures associated to the simulation of the operations described above. Iterative processes are used to determine the various parameters enounced above. They aim in particular at the verification of the electroneutrality of the sample. However, at first electroneutrality is rarely verified because the wine chemical analytical determination is never exhaustive. Therefore, we introduce the concept of «vinic acid» to compensate the negative ion deficit of usual wine chemical analytical determination. This «vinic acid» is describe as a diacid with a fixed second dissociation constant (pK2 = 5 and a first dissociation constant determined automatically by MEXTAR®. This enables MEXTAR® to simulate accurately experimental tartaric precipitations for several samples. Thanks to the predicting capacity of MEXTAR®, the correlation between the total polyphenol content (IPT in red wines and the difficulty to stabilise high IPT wine with respect to tartaric salts is confirmed. Finally, malolactic fermentations are also well simulated. A validation of MEXTAR® for the acid addition or removal has yet to be done when reliable experimental data are available.

Study on uranium loss during 'Iron-Gypsum Cake' precipitation from acid leach liquor of Jaduguda ore using factorially designed experiments

International Nuclear Information System (INIS)

Das, Amrita; Yadav, Manoj; Chatterjee, Ankur; Singh, A.K.; Hubli, R.C.

2012-01-01

Acid leaching process for uranium recovery from ore often generates considerable amounts of impurities into the solution. It is a challenge to separate the non-valuable impurities as manageable and stable waste products for final disposal, without losing the valuable constituents. The main impurities that come with the leach liquor are iron and sulfate. Their removal is essential for meeting the iron requirement in leaching circuit and also for making the effluent suitable for recycle. Factorial design analysis was applied to study of process variables for precipitation of iron and sulphate from leach liquor with composition using CaO as precipitation reagent

Mucuna pruriens (Konch Beej precipitates manic symptoms

Directory of Open Access Journals (Sweden)

Supriya Vaish

2014-01-01

Full Text Available Owing to the popular misconception that all ayurvedic preparations are completely safe, a vast majority of these are indiscriminately consumed by people procured as over the counter drugs. These preparations are combinations of multiple products that are often unidentified and dangerous and can precipitate various psychiatric symptoms. Hereby, we present a case of adolescent male in acute manic excitement after consumption of ayurvedic preparation containing "konchbeej" (Mucuna pruriens which is rich in l-3,4 dihydroxyphenyl alanine; precursor of dopamine.

Determination of furan precursors and some thermal damage markers in baby foods: ascorbic acid, dehydroascorbic acid, hydroxymethylfurfural and furfural.

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Mesías-García, Marta; Guerra-Hernández, Eduardo; García-Villanova, Belén

2010-05-26

The presence of ascorbic acid (AA), vitamin C (AA + dehydroascorbic acid (DHAA)) and furfural as potential precursors of furan in commercial fruit and vegetable jarred baby food was studied. Hydroxymethylfurfural (HMF) was also determined and used, together with furfural levels, as markers of thermal damage. AA, calculated DHAA and vitamin C values ranged between 22.4 and 103, 2.9 and 13.8, and 32.1 and 113.2 mg/100 g, respectively, in fruit-based baby food. However, no trace of AA was found in the vegetable-based baby food samples tested, probably because these samples are not enriched in vitamin C and the content of this vitamin in fresh vegetables is destroyed during processing. Furfural values ranged from not detected to 236 microg/100 g, being higher in vegetable samples than in fruit samples possibly because of greater AA degradation favored by a higher pH in the vegetable samples. HMF values (range: not detected-959 microg/100 g), however, were higher in the fruit samples, probably due to greater carbohydrate content degradation and as a consequence of the Maillard reaction, favored by a lower pH in these samples. According to these results, HMF would be the optimum indicator of thermal treatment for fruits, and furfural for vegetables. The higher furfural content of vegetable baby food could be considered an index of greater AA degradation and, therefore, the furan content might be higher in this kind of sample than in fruit-based baby food.

Metal and acidity fluxes controlled by precipitation/dissolution cycles of sulfate salts in an anthropogenic mine aquifer.

Science.gov (United States)

Cánovas, C R; Macías, F; Pérez-López, R

2016-05-01

Underground mine drainages are extremely difficult to study due to the lack of information about the flow path and source proximity in relation to the outflow adit. Geochemical processes controlling metals and acidity fluxes in a complex anthropogenic mine aquifer in SW Spain during the dry and rainy season were investigated by geochemical and statistical tools. High concentrations of acidity, sulfate, metals and metalloids (e.g. Fe, Cu, Zn, As, Cd, Ni, Co) were observed due to intense sulfide oxidation processes. The high residence time inside the anthropogenic aquifer, around 40days, caused the release of significant quantities of metals linked to host rocks (e.g. Al, Ca, Ge, Li, Mg, REE). The most outstanding characteristic of the acid mine drainage (AMD) outflows is the existence of higher Fe/SO4 molar ratios than those theoretical of pyrite (0.50) during most of the monitored period, due to a fire which occurred in 1949 and remained active for decades. Permanent and temporal retention mechanisms of acidity and metals were observed in the galleries. Once released from sulfide oxidation, Pb and As are sorbed on Fe oxyhydroxysulfate or precipitated as low solubility minerals (i.e. anglesite) inside the galleries. The precipitation of evaporitic sulfate salts during the dry season and the subsequent re-dissolution after rainfall control the fluxes of acidity and main metals (i.e. Fe, Mg, Al) from this anthropogenic aquifer. Some elements, such as Cd, Cu, Ni, REE and Zn, are retained in highly soluble sulfate salts while other elements, such as Ge, Pb and Sc, have a lower response to washout processes due to its incorporation in less soluble sulfate salts. In this way, metal concentration during the washout processes would be controlled by the proportion and solubility of each type of evaporitic sulfate salt stored during the dry season. The recovery of metals of economic interest contained in the AMD could help to self-finance the remediation of these waters in

Preventing Precipitation in the ISS Urine Processor

Science.gov (United States)

Muirhead, Dean; Carter, Layne; Williamson, Jill; Chambers, Antja

2017-01-01

The ISS Urine Processor Assembly (UPA) was initially designed to achieve 85% recovery of water from pretreated urine on ISS. Pretreated urine is comprised of crew urine treated with flush water, an oxidant (chromium trioxide), and an inorganic acid (sulfuric acid) to control microbial growth and inhibit precipitation. Unfortunately, initial operation of the UPA on ISS resulted in the precipitation of calcium sulfate at 85% recovery. This occurred because the calcium concentration in the crew urine was elevated in microgravity due to bone loss. The higher calcium concentration precipitated with sulfate from the pretreatment acid, resulting in a failure of the UPA due to the accumulation of solids in the Distillation Assembly. Since this failure, the UPA has been limited to a reduced recovery of water from urine to prevent calcium sulfate from reaching the solubility limit. NASA personnel have worked to identify a solution that would allow the UPA to return to a nominal recovery rate of 85%. This effort has culminated with the development of a pretreatment based on phosphoric acid instead of sulfuric acid. By eliminating the sulfate associated with the pretreatment, the brine can be concentrated to a much higher concentration before calcium sulfate reach the solubility limit. This paper summarizes the development of this pretreatment and the testing performed to verify its implementation on ISS.

Non radioactive precursor import into chloroplasts

International Nuclear Information System (INIS)

Lombardo, V.A.; Ottado, J.

2003-01-01

Full text: Eukaryotic cells have a subcellular organization based on organelles. Protein transport to these organelles is quantitatively important because the majority of cellular proteins are codified in nuclear genes and then delivered to their final destination. Most of the chloroplast proteins are translated on cytoplasmic ribosomes as larger precursors with an amino terminal transit peptide that is necessary and sufficient to direct the precursor to the chloroplast. Once inside the organelle the transit peptide is cleaved and the mature protein adopts its folded form. In this work we developed a system for the expression and purification of the pea ferredoxin-NADP + reductase precursor (preFNR) for its import into chloroplasts in non radioactive conditions. We constructed a preFNR fused in its carboxy terminus to a 6 histidines peptide (preFNR-6xHis) that allows its identification using a commercial specific antibody. The construction was expressed, purified, processed and precipitated, rendering a soluble and active preFNR-6xHis that was used in binding and import into chloroplasts experiments. The reisolated chloroplasts were analyzed by SDS-PAGE, electro-blotting and revealed by immuno-detection using either colorimetric or chemiluminescent reactive. We performed also import experiments labeling preFNR and preFNR-6xHis with radioactive methionine as controls. We conclude that preFNR-6xHis is bound and imported into chloroplasts as the wild type preFNR and that both colorimetric or chemiluminescent detection methods are useful to avoid the manipulation of radioactive material. (author)

Metal transport and remobilisation in a basin affected by acid mine drainage: the role of ochreous amorphous precipitates.

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Consani, Sirio; Carbone, Cristina; Dinelli, Enrico; Balić-Žunić, Tonci; Cutroneo, Laura; Capello, Marco; Salviulo, Gabriella; Lucchetti, Gabriella

2017-06-01

Metal-polluted mine waters represent a major threat to the quality of waters and sediments in a downstream basin. At the confluence between acidic mine waters and the unpolluted waters of the Gromolo Torrent (Liguria, North-West Italy), the massive formation of an ochreous amorphous precipitate takes place. This precipitate forms a soft blanket that covers the torrent bed and can be observed down to its mouth in the sea. The aim of this work is to evaluate the dispersion of metals in the Gromolo Torrent basin from the abandoned Cu-Fe sulphide mine of Libiola to the Ligurian Sea and to assess the metal remobilisation from the amorphous precipitates. The mineralogy of the superficial sediments collected in the torrent bed and the concentrations of different elements of environmental concern (Cu, Zn, Cd, Co, Cr, Mn, Ni, Pb, As, and Sb) were therefore analysed. The results showed that the precipitates contain high concentration of Fe, Al, Cu, and Zn, significantly modifying the bulk chemistry of the Gromolo Torrent sediments. In order to evaluate the possible remobilisation of ecotoxic elements from the amorphous precipitates, bulk leaching tests were performed with both deionised and seawater. Bulk leaching tests with deionised water mobilised primarily high Pb amounts, but also relatively high concentrations of Fe, Al, Cu, and Zn are released in the leachate. In seawater tests, Fe, Al, Cu, and Zn were released in smaller amounts, while other elements like Mn, Cd, Co, and Ni increased in the released fraction. Pb was still strongly released as in deionised water experiments. The results show that the interaction of precipitates and seawater can remobilise high concentrations of metals, thus affecting the surrounding environment.

The production of rare earth elements group via tributyl phosphate extraction and precipitation stripping using oxalic acid

OpenAIRE

Jorjani, Esmaeil; Shahbazi, Malek

2016-01-01

In this study, solvent extraction and precipitation stripping were used to produce rare earth elements (REEs). Tributyl phosphate (TBP) was used to extract yttrium, lanthanum, cerium, and neodymium from an aqueous solution produced by nitric acid leaching of apatite concentrate. In the extraction stage, the effects of TBP concentration, pH, contact time, temperature, and phase ratio were investigated. The results show that about 95%, 90%, 87% and 80% of neodymium, cerium, lanthanum, and yttri...

Determination of trifluoroacetic acid in 1996--1997 precipitation and surface waters in California and Nevada

Energy Technology Data Exchange (ETDEWEB)

Wujcik, C.E.; Cahill, T.M.; Seiber, J.N. [Univ. of Nevada, Reno, NV (United States)

1999-05-15

The atmospheric degradation of three chlorofluorocarbon (CFC) replacement compounds, namely HFC-134a, HCFC-123, and HCFC-124, results in the formation of trifluoroacetic acid (TFA). Concentrations of TFA were determined in precipitation and surface water samples collected in California and Nevada during 1996--1997. Terminal lake systems were found to have concentrations 4--13 times higher than their calculated yearly inputs, providing evidence for accumulation. The results support dry deposition as the primary contributor of TFA to surface waters in arid and semiarid environments. Precipitation samples obtained from three different locations contained 20.7--1530 ng/L with significantly higher concentrations in fogwater over rainwater. Elevated levels of TFA were observed for rainwater collected in Nevada over those collected in California, indicating continual uptake and concentration as clouds move from a semiarid to arid climate. Thus several mechanisms exist, including evaporative concentration, vapor-liquid phase partitioning, lowered washout volumes of atmospheric deposition water, and dry deposition, which may lead to elevated concentrations of TFA in atmospheric and surface waters above levels expected from usual rainfall washout.

Contribution of precursor compounds to the release of per- and polyfluoroalkyl substances (PFASs) from waste water treatment plants (WWTPs).

Science.gov (United States)

Eriksson, Ulrika; Haglund, Peter; Kärrman, Anna

2017-11-01

Per- and polyfluoroalkyl substances (PFASs) are ubiquitous in sludge and water from waste water treatment plants, as a result of their incorporation in everyday products and industrial processes. In this study, we measured several classes of persistent PFASs, precursors, transformation intermediates, and newly identified PFASs in influent and effluent sewage water and sludge from three municipal waste water treatment plants in Sweden, sampled in 2015. For sludge, samples from 2012 and 2014 were analyzed as well. Levels of precursors in sludge exceeded those of perfluoroalkyl acids and sulfonic acids (PFCAs and PFSAs), in 2015 the sum of polyfluoroalkyl phosphoric acid esters (PAPs) were 15-20ng/g dry weight, the sum of fluorotelomer sulfonic acids (FTSAs) was 0.8-1.3ng/g, and the sum of perfluorooctane sulfonamides and ethanols ranged from non-detected to 3.2ng/g. Persistent PFSAs and PFCAs were detected at 1.9-3.9ng/g and 2.4-7.3ng/g dry weight, respectively. The influence of precursor compounds was further demonstrated by an observed substantial increase for a majority of the persistent PFCAs and PFSAs in water after waste water treatment. Perfluorohexanoic acid (PFHxA), perfluorooctanoic acid (PFOA), perfluorohexane sulfonic acid (PFHxS), and perfluorooctane sulfonic acid (PFOS) had a net mass increase in all WWTPs, with mean values of 83%, 28%, 37% and 58%, respectively. The load of precursors and intermediates in influent water and sludge combined with net mass increase support the hypothesis that degradation of precursor compounds is a significant contributor to PFAS contamination in the environment. Copyright © 2017. Published by Elsevier B.V.

Saccharomyces kudriavzevii and Saccharomyces uvarum differ from Saccharomyces cerevisiae during the production of aroma-active higher alcohols and acetate esters using their amino acidic precursors.

Science.gov (United States)

Stribny, Jiri; Gamero, Amparo; Pérez-Torrado, Roberto; Querol, Amparo

2015-07-16

Higher alcohols and acetate esters are important flavour and aroma components in the food industry. In alcoholic beverages these compounds are produced by yeast during fermentation. Although Saccharomyces cerevisiae is one of the most extensively used species, other species of the Saccharomyces genus have become common in fermentation processes. This study analyses and compares the production of higher alcohols and acetate esters from their amino acidic precursors in three Saccharomyces species: Saccharomyces kudriavzevii, Saccharomyces uvarum and S. cerevisiae. The global volatile compound analysis revealed that S. kudriavzevii produced large amounts of higher alcohols, whereas S. uvarum excelled in the production of acetate esters. Particularly from phenylalanine, S. uvarum produced the largest amounts of 2-phenylethyl acetate, while S. kudriavzevii obtained the greatest 2-phenylethanol formation from this precursor. The present data indicate differences in the amino acid metabolism and subsequent production of flavour-active higher alcohols and acetate esters among the closely related Saccharomyces species. This knowledge will prove useful for developing new enhanced processes in fragrance, flavour, and food industries. Copyright © 2015. Published by Elsevier B.V.

H and C NMR investigations of Pb(Zr,Ti)O3 thin-film precursor solutions

International Nuclear Information System (INIS)

Assink, R.A.; Schwartz, R.W.

1993-01-01

Solvent reactions, ligand substitutions, and the oligomer/polymer backbone structure are important factors in the solution preparation of ceramic films. In this study the authors have used H and C NMR spectroscopy to characterize solvent and ligand effects in precursor solutions used for the deposition of ferroelectric PZT (lead zirconate titanate) thin films. Solutions were prepared by a sequential precursor addition method from carboxylate and alkoxide precursors of the three cations, and the solvent, acetic acid, methanol, and water. The results indicate that acetic acid was a key component in the solution preparation process. As observed previously for single metallic component systems, its presence resulted in esterification reactions, leading in the present case to the formation of methyl, isopropyl, and n-butyl acetates. Second, acetic acid functioned as a chemical modifier, or chelating agent, replacing essentially all of the alkoxy ligands of the original precursors. Since alkoxy replacement appeared to be complete, we may describe the PZT species formed in solution as oxo acetate in nature. Finally, the solvent and ligand behavior of a solution prepared by an inverted mixing order was compared to the behavior of the solution prepared by a sequential precursor addition. The spectra for the two solutions were similar, and only differences in the relative intensities of the ester and alcoholic resonances were observed. 29 refs., 5 figs., 3 tabs

Hydroxide precursors to produce nanometric YCrO{sub 3}: Characterization and conductivity analysis

Energy Technology Data Exchange (ETDEWEB)

Durán, A., E-mail: dural@cnyn.unam.mx [Universidad Nacional Autónoma de México, Centro de Nanociencias y Nanotecnología, Km. 107 Carretera Tijuana-Ensenada, Apartado Postal 14, C.P. 22800, Ensenada, B.C. (Mexico); Meza F, C. [Universidad Nacional Autónoma de México, Centro de Nanociencias y Nanotecnología, Km. 107 Carretera Tijuana-Ensenada, Apartado Postal 14, C.P. 22800, Ensenada, B.C. (Mexico); Arizaga, Gregorio Guadalupe Carbajal, E-mail: gregoriocarbajal@yahoo.com.mx [Departamento de Química, Universidad de Guadalajara, Marcelino García Barragán 1421, C.P. 44430, Guadalajara, Jalisco (Mexico)

2012-06-15

Highlights: ► Y/Cr mixed hydroxide was precipitated with gaseous ammonia. ► The hydroxide treated at 1373 K formed YCrO{sub 3} crystals with 20 nm diameter. ► Electrical properties were different than those found in other methods of synthesis. ► E{sub act} suggests small-polarons as conduction mechanisms. -- Abstract: A precursor to produce perovskite-type YCrO{sub 3} was precipitated by bubbling gaseous ammonia into an yttrium/chromium salts solution. X-ray diffraction showed that the as-prepared powders were amorphous. Thermal treatment between 1273 and 1373 K, leads to formation of polycrystalline YCrO{sub 3} with crystal sizes around 20 nm. High resolution X-ray photoelectron spectra showed uniform chemical environment for yttrium and chromium in the amorphous hydroxide and crystalline YCrO{sub 3}. Shifts between Y 3d{sub 5/2} and Cr 2p{sub 3/2} binding energy suggest redistribution or charge transfer between yttrium and chromium ions in the YCrO{sub 3} structure. The electrical properties of YCrO{sub 3}, whose precursors were precipitated with gaseous ammonia are different than those prepared by combustion synthesis. Electrical conductivity presents a sudden increase at ∼473 K, which is associated to the grain size and morphology of the crystallites. The redistribution of charge between Y(III) and Cr(III) is thermally activated by the hopping of small-polarons, which are characterized by the Arrhenius law as the conductive mechanism.

Synthesis of WO3 nanoparticles by citric acid-assisted precipitation and evaluation of their photocatalytic properties

International Nuclear Information System (INIS)

Sánchez-Martínez, D.; Martínez-de la Cruz, A.; López-Cuéllar, E.

2013-01-01

Graphical abstract: Display Omitted Highlights: ► WO 3 nanoparticles were synthesized by a simple citric acid-assisted precipitation. ► WO 3 photocatalyst was able to the partial mineralization of rhB, IC and MO. ► WO 3 can be considered as a photocatalyst active under visible light irradiation. -- Abstract: WO 3 nanoparticles were synthesized by citric acid-assisted precipitation method using a 1:1.5 molar ratio of ammonium paratungstate hydrate (H 42 N 10 O 42 W 12 ·xH 2 O):citric acid (C 6 H 8 O 7 ). The formation of monoclinic crystal structure of WO 3 at different temperatures was confirmed by X-ray powder diffraction (XRD). The characterization of the samples synthesized was complemented by transmission electron microscopy (TEM), Brunauer–Emmitt–Teller surface area (BET) and diffuse reflectance spectroscopy (DRS). According to the thermal treatment followed during the synthesis of WO 3 , the morphology of the nanoparticles formed was characterized by rectangular and ovoid shapes. The photocatalytic activity of WO 3 obtained under different experimental conditions was evaluated in the degradation of rhodamine B (rhB), indigo carmine (IC), methyl orange (MO), and Congo red (CR) in aqueous solution under UV and UV–vis radiation. The highest photocatalytic activity was observed in the sample obtained by thermal treatment at 700 °C. In general, the sequence of degradation of the organic dyes was: indigo carmine (IC) > rhodamine B (rhB) > methyl orange (MO) > Congo red (CR). The mineralization degree of organic dyes by WO 3 photocatalysts was determined by total organic carbon analysis (TOC) reaching percentages of mineralization of 82% (rhB), 85% (IC), 28% (MO), and 7% (CR) for 96 h of lamp irradiation.

Inducing mineral precipitation in groundwater by addition of phosphate

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Hartmann Thomas

2011-10-01

Full Text Available Abstract Background Induced precipitation of phosphate minerals to scavenge trace elements from groundwater is a potential remediation approach for contaminated aquifers. The success of engineered precipitation schemes depends on the particular phases generated, their rates of formation, and their long term stability. The purpose of this study was to examine the precipitation of calcium phosphate minerals under conditions representative of a natural groundwater. Because microorganisms are present in groundwater, and because some proposed schemes for phosphate mineral precipitation rely on stimulation of native microbial populations, we also tested the effect of bacterial cells (initial densities of 105 and 107 mL-1 added to the precipitation medium. In addition, we tested the effect of a trace mixture of propionic, isovaleric, formic and butyric acids (total concentration 0.035 mM. Results The general progression of mineral precipitation was similar under all of the study conditions, with initial formation of amorphous calcium phosphate, and transformation to poorly crystalline hydroxylapatite (HAP within one week. The presence of the bacterial cells appeared to delay precipitation, although by the end of the experiments the overall extent of precipitation was similar for all treatments. The stoichiometry of the final precipitates as well as Rietveld structure refinement using x-ray diffraction data indicated that the presence of organic acids and bacterial cells resulted in an increasing a and decreasing c lattice parameter, with the higher concentration of cells resulting in the greatest distortion. Uptake of Sr into the solids was decreased in the treatments with cells and organic acids, compared to the control. Conclusions Our results suggest that the minerals formed initially during an engineered precipitation application for trace element sequestration may not be the ones that control long-term immobilization of the contaminants. In

Studies on gadolinium precipitation in moderator system of nuclear reactor

International Nuclear Information System (INIS)

Joshi, Akhilesh C.; Rajesh, Puspalata; Rufus, A.L.; Velmurugan, S.

2015-01-01

Gadolinium is used in the moderator system of many Pressurised Heavy Water Reactors (PHWRs) for start-up, shut-down and reactivity control during operation. It is very much essential to maintain gadolinium concentration in the system as desired. It has been reported that gadolinium gets precipitated in as oxalate in carbonated water under the influence of γ-radiation. Hence, studies were carried out to investigate the effect of dose, presence of other metal ions and metal surfaces on the precipitation of gadolinium. The results showed that the amount of carboxylic acids viz., formic acid and oxalic acid, formed due to radiolysis is dependent on the dose and that the curve passes though a maxima. Gadolinium is added in higher concentration in Advanced Heavy Water Reactor. So, experiments with high concentration of gadolinium were also carried out. Ultra pure water saturated with high purity CO 2 containing gadolinium and desired ion/surface was irradiated with γ-radiation from 60 Co source at 25°C to doses ranging from 2.5-16.6 Mrad. At lower doses, formation of carboxylic acids takes place but as the dose increases, decomposition of these acids starts and hence the concentration Vs dose passes through a maximum. It was found that precipitation of gadolinium as oxalate occurred at lower doses. At higher doses, it was seen that pH of the solution decreases and hence solubility of gadolinium oxalate increases. It was also observed that the amount of gadolinium precipitated varied linearly with the initial concentration of gadolinium varying from 2 ppm to 20 ppm. While for gadolinium concentration from 20 ppm to 400 ppm, gadolinium in particulate form was observed. The amount of carboxylic acids formed depends on the nature of cations present in solution. It was found that the amount of oxalic acid formed in the case of gadolinium was more than that formed in the case of sodium. Presence of metal oxides such as ZrO 2 formed over zircoloy surfaces was found to

2-keto-4-(methylthio)butyric acid (keto analog of methionine) is a safe and efficacious precursor of L-methionine in chicks.

Science.gov (United States)

Dilger, Ryan N; Kobler, Christoph; Weckbecker, Christoph; Hoehler, Dirk; Baker, David H

2007-08-01

Relative bioefficacy and toxicity of Met precursor compounds were investigated in young chicks. The effectiveness of DL-Met and 2-keto-4-(methylthio)butyric acid (Keto-Met) to serve as L-Met precursors was quantified using Met-deficient diets of differing composition. Efficacy was based on slope-ratio and standard-curve methodology. Using L-Met as a standard Met source added to a purified diet, DL-Met and Keto-Met were assigned relative bioefficacy values of 98.5 and 92.5%, respectively, based on weight gain. Relative bioefficacy values of 98.5 and 89.3% were assigned to DL-Met and Keto-Met, respectively, when chicks were fed a Met-deficient, corn-soybean meal-peanut meal diet. Thus, both DL-Met and Keto-Met are effective Met precursor compounds in chicks. Additionally, growth-depressing effects of L-Met, DL-Met, and Keto-Met were compared using a nutritionally adequate corn-soybean meal diet supplemented with 15 or 30 g/kg of each compound. Similar reductions in weight gain, food intake, and gain:food ratio were observed for each compound. Subjective spleen color scores, indicative of splenic hemosiderosis, increased linearly (P Keto-Met to L-Met in vivo merely requires transamination, Keto-Met may prove to be a useful supplement not only in food animal production, but also as a component of enteral and parenteral formulas for humans suffering from renal insufficiency.

Bioavailability of zinc to rats from defatted soy flour, acid-precipitated soy concentrate and neutralized soy concentrate as determined by intrinsic and extrinsic labeling techniques

International Nuclear Information System (INIS)

Ketelsen, S.M.; Stuart, M.A.; Weaver, C.M.; Forbes, R.M.; Erdman, J.W. Jr.

1984-01-01

The bioavailability of 65Zn from intrinsically and extrinsically labeled soy flour, acid-precipitated soy concentrate and neutralized soy concentrate was evaluated in rats. Weanling rats were fed marginally zinc-deficient diets, providing 8 ppm zinc from one of these three soy products, for 7 days. The rats then received a radioactively labeled test meal, identical in composition to the previous diet except that the soy product was either intrinsically or extrinsically labeled with 65Zn. After the test meal the rats were again fed diets the same as those consumed prior to the test meal. Whole-body retention of 65Zn at 24 hours and 12 days as well as 65Zn retained in tibias of rats given meals containing neutralized concentrate-based meals was significantly lower than for rats given meals containing the soy flour or acid-precipitated concentrate. In addition, retention of 65Zn from the extrinsically labeled acid-precipitated concentrate-based meal was significantly higher than from the same product intrinsically labeled. These findings confirm the results of previous feeding studies from which it was suggested that neutralization of soy protein concentrates reduces zinc bioavailability to the rat. In addition, the results are taken to suggest that experimental conditions may influence the validity of the extrinsic labeling technique for zinc

Alteration of tricarboxylic acid cycle metabolism in rat brain slices by halothane

International Nuclear Information System (INIS)

Cheng, S.C.; Brunner, E.A.

1978-01-01

Metabolism of [2- 14 C] pyruvate, [1- 14 C] acetate and [5- 14 C] citrate in rat cerebral cortex slices was studied in the presence of halothane. Metabolites assayed include acetylcholine (ACh), citrate, glutamate, glutamineγ-aminobutyrate (GABA) and aspartate. The trichloroacetic acid soluble extract, the trichloracetic acid insoluble precipitate and its lipid extract were also studied. In control experiments, pyruvate preferentially labelled ACh, citrate, glutamate, GABA and aspartate. Acetate labelled ACh, but to a lesser extent than pyruvate. Acetate also labelled lipids and glutamine. Citrate labelled lipids but not ACh and served as a preferential precursor for glutamine. These data support a three-compartment model for cerebral tricarboxylic acid cycle metabolism. Halothane caused increases in GABA and aspartate contents and a decrease in ACh content. It has no effect on the contents of citrate, glutamate and glutamine. Halothane preferentially inhibited the metabolic transfer of radioactivity from pyruvate into almost all metabolites, an effect probably not related to pyruvate permeability. This is interpreted as halothane depression of the large metabolic compartment which includes the nerve endings. Halothane increased the metabolic transfer of radioactivity from acetate into lipids but did not alter such a transfer into the trichloroacetic acid extract. Halothane increased the metabolic transfer of radioactivity from citrate into the trichloroacetic acid precipitate, lipids and especially glutamine. Transfer of citrate radioactivity into GABA was somewhat decreased. The differential effects of halothane on acetate and citrate utilization suggest that the small metabolic compartment should be subdivided. Therefore, at least three metabolic compartments are demonstrated. Halothane did not interfere with the dicarboxylic acid portion of the tricarboxylic acid cycle. (author)

Trends of two decadal precipitation chemistry in a subtropical rainforest in East Asia.

Science.gov (United States)

Chang, Chung-Te; Wang, Chiao-Ping; Huang, Jr-Chuan; Wang, Lih-Jih; Liu, Chiung-Pin; Lin, Teng-Chiu

2017-12-15

Long-term monitoring of precipitation chemistry provides a great opportunity to examine the evolution of air pollutant emissions and effectiveness of air pollution control measures. We evaluated the characteristics and trends of precipitation chemistry at both annual and seasonal scales based on the records of 1994-2013 at Fushan Experimental Forest (FEF) of northeastern Taiwan. The results showed that 77% of the weekly precipitation had pHprecipitation pH and the difference between [SO 4 2 - +NO 3 - ] and [Ca 2+ +NH 4 + ], not just [SO 4 2 - +NO 3 - ], suggesting that precipitation acidity was not solely determined by acidic pollutants but by the balance between acidic pollutants and base cations. We also found temporal decreases of Ca 2+ and NH 4 + concentrations in precipitation which contributed to the low acid neutralization capacity of precipitation. Annual deposition of NO 3 - and SO 4 2- was 23 and 55kgha -1 yr -1 , which is much higher than most forest sites in the industrialized countries suggesting that acid deposition is still a major environmental issue in Taiwan. Annual deposition of NH 4 + , Ca 2+ and NO 3 - showed significant decreasing trends during the 20-year period, which was mostly due to the decreases in the summer deposition associated with air pollution mitigation strategies. Winter deposition showed no decreasing patterns for the same period. The high contribution to annual acid deposition from autumn-winter and spring rains (50%) associated with northeast monsoon implies that long-range transport of anthropogenic emissions from East Asia played a key role on acid depositions at FEF and possibly many areas in the region. Therefore, intergovernmental cooperation is urgently needed to effectively mitigate the threat of acid deposition in East Asia. Copyright © 2017 Elsevier B.V. All rights reserved.

New composite materials prepared by calcium phosphate precipitation in chitosan/collagen/hyaluronic acid sponge cross-linked by EDC/NHS.

Science.gov (United States)

Kaczmarek, B; Sionkowska, A; Kozlowska, J; Osyczka, A M

2018-02-01

Nowadays, fabrication of composite materials based on biopolymers is a rising field due to potential for bone repair and tissue engineering application. Blending of different biopolymers and incorporation of inorganic particles in the blend can lead to new materials with improved physicochemical properties and biocompatibility. In this work 3D porous structures called scaffolds based on chitosan, collagen and hyaluronic acid were obtained through the lyophilization process. Scaffolds were cross-linked by EDC/NHS. Infrared spectra for the materials were made, the percentage of swelling, scaffolds porosity and density, mechanical parameters, thermal stability were studied. Moreover, the scaffolds were used as matrixes for the calcium phosphate in situ precipitation. SEM images were taken and EDX analysis was carried out for calcium and phosphorous content determination in the scaffold. In addition, the adhesion and proliferation of human osteosarcoma SaOS-2 cells was examined on obtained scaffolds. The results showed that the properties of 3D composites cross-linked by EDC/NHS were altered after the addition of 1, 2 and 5% hyaluronic acid. Mechanical parameters, thermal stability and porosity of scaffolds were improved. Moreover, calcium and phosphorous were found in each kind of scaffold. SEM images showed that the precipitation was homogeneously carried in the whole volume of samples. Attachment of SaOS-2 cells to all modified materials was better compared to unmodified control and proliferation of these cells was markedly increased on scaffolds with precipitated calcium phosphate. Obtained materials can provide the support useful in tissue engineering and regenerative medicine. Copyright © 2017 Elsevier B.V. All rights reserved.

Characterization of Lignin Precipitated From The Soda Black Liquor of Oil Palm Empty Fruit Bunch Fibers by Various Mineral Acids

Directory of Open Access Journals (Sweden)

M.N Mohamad Ibrahim

2017-10-01

Full Text Available Soda lignin from oil palm empty fruit bunch was directly isolated by various mineral acids i.e. sulfuric acid, hydrochloric acid, phosphoric acid and nitric acid at three levels of concentration (20% v/v, 60%v/v and concentrated. A comparison study was performed through physicochemical properties and structural features using FT-IR, UV, 13C-NMR and nitrobenzene oxidation. The FT-IR results showed that there is no significant difference between the main structures of the lignin isolated by various acids. However, low concentration of phosphoric acid is preferable because of its highest yield. The S: V: H ratio of 7-15:6-11:1 as evaluated by the nitrobenzene oxidation procedure suggests that soda lignin can be classified as belonging to either the cereal straw on grass type. The UV results indicate that phosphoric acid consistently gave the highest absorbance value among the four acids tested in this study regardless of its concentration level. The C13-FTNMR spectra, suggest that the lignin structure is independent of the type of acid used for precipitation.

Well acidizing

Energy Technology Data Exchange (ETDEWEB)

Street, E H

1980-01-23

The apparatus relates in particular to a well-treating process in which an aqueous acid solution having a pH of < 2 is injected into a subterranean reservoir in a manner such that materials that contain ferric ions are present in the acid and, as the acid reacts within the reservoir and attains a pH exceeding 3, tend to be precipitated as ferric ion-containing solid materials that may plug the pores of the reservoir. Such a precipitation is prevented by dissolving in the acid solution an amount of 5-sulfosalicylic acid which is at least sufficient to sequester significant proportions of ferric ions when the pH of the acid is from 0.5 to 3 but is less than enough to cause a significant salting-out of solid materials, and an amount of citric acid which is at least sufficient to sequester significant proportions of ferric ions when the pH of the acid is from 3 to 6 but is less than enough to precipitate a significant amount of calcium citrate. The amount of the 5-sulfosalicylic acid may be from 0.01 to 0.05 moles/l and the amount of citric acid is from 0.001 to 0.009 moles/l. 11 claims.

Caracterización de recubrimientos sintetizados por el método de los precursores poliméricos

Directory of Open Access Journals (Sweden)

Jorge Hernando Bautista Ruiz

2012-03-01

Full Text Available Ceramic films were formed SiO2-TiO2 system synthesized by the polymeric precursor method from tetraethyl orthosilicate (TEOS and Titanium tetrabutoxide (TBT, a hydroxycarboxylic acid (citric acid and polyhydric alcohol (ethylene glycol. The films were deposited monolayer on substrates of AISI 304 steel using the immersion technique (dip-coating. Concentrations were used as precursors Si (silicon 10% Ti (Titanium 90%, Si 30% Ti 70% and Si 50% Ti 50% in the system. The influence of coatings on corrosion behavior of the substrate in a solution of hydrochloric acid (HCl, using the technique of Electrochemical Impedance Spectroscopy (EIS. Additionally, the topography was evaluated by scanning electronmicroscopy (SEM and adhesion of coatings to the substrate. It was found that the values of these parameters change substantially depending on the concentrations of the precursors used in synthesis.

Capability of cation exchange technology to remove proven N-nitrosodimethylamine precursors.

Science.gov (United States)

Li, Shixiang; Zhang, Xulan; Bei, Er; Yue, Huihui; Lin, Pengfei; Wang, Jun; Zhang, Xiaojian; Chen, Chao

2017-08-01

N-nitrosodimethylamine (NDMA) precursors consist of a positively charged dimethylamine group and a non-polar moiety, which inspired us to develop a targeted cation exchange technology to remove NDMA precursors. In this study, we tested the removal of two representative NDMA precursors, dimethylamine (DMA) and ranitidine (RNTD), by strong acidic cation exchange resin. The results showed that pH greatly affected the exchange efficiency, with high removal (DMA>78% and RNTD>94%) observed at pHMg 2+ >RNTD + >K + >DMA + >NH 4 + >Na + . The partition coefficient of DMA + to Na + was 1.41±0.26, while that of RNTD + to Na + was 12.1±1.9. The pseudo second-order equation fitted the cation exchange kinetics well. Bivalent inorganic cations such as Ca 2+ were found to have a notable effect on NA precursor removal in softening column test. Besides DMA and RNTD, cation exchange process also worked well for removing other 7 model NDMA precursors. Overall, NDMA precursor removal can be an added benefit of making use of cation exchange water softening processes. Copyright © 2017. Published by Elsevier B.V.

Solution synthesis of mixed-metal chalcogenide nanoparticles and spray deposition of precursor films

Science.gov (United States)

Schulz, Douglas L.; Curtis, Calvin J.; Ginley, David S.

2000-01-01

A colloidal suspension comprising metal chalcogenide nanoparticles and a volatile capping agent. The colloidal suspension is made by reacting a metal salt with a chalcogenide salt in an organic solvent to precipitate a metal chalcogenide, recovering the metal chalcogenide, and admixing the metal chalcogenide with a volatile capping agent. The colloidal suspension is spray deposited onto a substrate to produce a semiconductor precursor film which is substantially free of impurities.

A second pathway to degrade pyrimidine nucleic acid precursors in eukaryotes

DEFF Research Database (Denmark)

Andersen, Gorm; Bjornberg, Olof; Polakova, Silvia

2008-01-01

Pyrimidine bases are the central precursors for RNA and DNA, and their intracellular pools are determined by de novo, salvage and catabolic pathways. In eukaryotes, degradation of uracil has been believed to proceed only via the reduction to dihydrouracil. Using a yeast model, Saccharomyces kluyv...... of the eukaryotic or prokaryotic genes involved in pyrimidine degradation described to date.......Pyrimidine bases are the central precursors for RNA and DNA, and their intracellular pools are determined by de novo, salvage and catabolic pathways. In eukaryotes, degradation of uracil has been believed to proceed only via the reduction to dihydrouracil. Using a yeast model, Saccharomyces......, respectively. The gene products of URC1 and URC4 are highly conserved proteins with so far unknown functions and they are present in a variety of prokaryotes and fungi. In bacteria and in some fungi, URC1 and URC4 are linked on the genome together with the gene for uracil phosphoribosyltransferase (URC6). Urc1...

Acid rain abatement in Belgium: lessons in cost-effectiveness studies

International Nuclear Information System (INIS)

Cuijpers, C.; Proost, S.

1992-01-01

In this paper a cost-effectiveness analysis is presented for combating emissions of acid precursors. The focus of concern is to reach the environmental quality goal at least cost. Two cost-effective approaches are elaborated. Firstly, the maximum allowable emission of each acid precursor seperately is allocated in a cost-effective way across the economic sectors. Secondly, the maximum allowable emissions of acid precursors are allocated in a cost-effective way across the three considered acid precursors as well as across the economic sectors. It is argued that not only the energy consumption but also the agricultural sector could play an important role in a cost-effective strategy by curtailing its ammonia emissions. 6 refs., 8 figs., 1 tab

The presence of modifiable residues in the core peptide part of precursor nisin is not crucial for precursor nisin interactions with NisB- and NisC.

Directory of Open Access Journals (Sweden)

Rustem Khusainov

Full Text Available Precursor nisin is a model posttranslationally modified precursor lantibiotic that can be structurally divided into a leader peptide sequence and a modifiable core peptide part. The nisin core peptide clearly plays an important role in the precursor nisin-nisin modification enzymes interactions, since it has previously been shown that the construct containing only the nisin leader sequence is not sufficient to pull-down the nisin modification enzymes NisB and NisC. Serines and threonines in the core peptide part are the residues that NisB specifically dehydrates, and cysteines are the residues that NisC stereospecifically couples to the dehydrated amino acids. Here, we demonstrate that increasing the number of negatively charged residues in the core peptide part of precursor nisin, which are absent in wild-type nisin, does not abolish binding of precursor nisin to the modification enzymes NisB and NisC, but dramatically decreases the antimicrobial potency of these nisin mutants. An unnatural precursor nisin variant lacking all serines and threonines in the core peptide part and an unnatural precursor nisin variant lacking all cysteines in the core peptide part still bind the nisin modification enzymes NisB and NisC, suggesting that these residues are not essential for direct interactions with the nisin modification enzymes NisB and NisC. These results are important for lantibiotic engineering studies.

Functional Nanoporous Polymers from Block Copolymer Precursors

DEFF Research Database (Denmark)

Guo, Fengxiao

Abstract Self-assembly of block copolymers provides well-defined morphologies with characteristic length scales in the nanometer range. Nanoporous polymers prepared by selective removal of one block from self-assembled block copolymers offer great technological promise due to their many potential...... functionalities remains a great challenge due to the limitation of available polymer synthesis and the nanoscale confinement of the porous cavities. The main topic of this thesis is to develop methods for fabrication of functional nanoporous polymers from block copolymer precursors. A method has been developed......, where living anionic polymerization and atom transfer radical polymerization (ATRP) are combined to synthesize a polydimethylsiloxane-b-poly(tert-butyl acrylate)-b-polystyrene (PDMS-b-PtBA-b-PS) triblock copolymer precursor. By using either anhydrous hydrogen fluoride or trifluoroacetic acid, PtBA block...

Uranium (III) precipitation in molten chloride by wet argon sparging

Energy Technology Data Exchange (ETDEWEB)

Vigier, Jean-François, E-mail: jean-francois.vigier@ec.europa.eu [CEA, Nuclear Energy Division, Radiochemistry & Processes Department, F-30207 Bagnols sur Cèze (France); Unité de Catalyse et de Chimie du Solide, UCCS UMR CNRS 8181, Univ. Lille Nord de France, ENSCL-USTL, B.P. 90108, 59652 Villeneuve d' Ascq Cedex (France); Laplace, Annabelle [CEA, Nuclear Energy Division, Radiochemistry & Processes Department, F-30207 Bagnols sur Cèze (France); Renard, Catherine [Unité de Catalyse et de Chimie du Solide, UCCS UMR CNRS 8181, Univ. Lille Nord de France, ENSCL-USTL, B.P. 90108, 59652 Villeneuve d' Ascq Cedex (France); Miguirditchian, Manuel [CEA, Nuclear Energy Division, Radiochemistry & Processes Department, F-30207 Bagnols sur Cèze (France); Abraham, Francis [Unité de Catalyse et de Chimie du Solide, UCCS UMR CNRS 8181, Univ. Lille Nord de France, ENSCL-USTL, B.P. 90108, 59652 Villeneuve d' Ascq Cedex (France)

2016-06-15

In the context of pyrochemical processes for nuclear fuel treatment, the precipitation of uranium (III) in molten salt LiCl-CaCl{sub 2} (30–70 mol%) at 705 °C is studied. First, this molten chloride is characterized with the determination of the water dissociation constant. With a value of 10{sup −4.0}, the salt has oxoacid properties. Then, the uranium (III) precipitation using wet argon sparging is studied. The salt is prepared using UCl{sub 3} precursor. At the end of the precipitation, the salt is totally free of solubilized uranium. The main part is converted into UO{sub 2} powder but some uranium is lost during the process due to the volatility of uranium chloride. The main impurity of the resulting powder is calcium. The consequences of oxidative and reductive conditions on precipitation are studied. Finally, coprecipitation of uranium (III) and neodymium (III) is studied, showing a higher sensitivity of uranium (III) than neodymium (III) to precipitation. - Highlights: • Precipitation of Uranium (III) is quantitative in molten salt LiCl-CaCl{sub 2} (30–70 mol%). • The salt is oxoacid with a water dissociation constant of 10{sup −4.0} at 705 °C. • Volatility of uranium chloride is strongly reduced in reductive conditions. • Coprecipitation of U(III) and Nd(III) leads to a consecutive precipitation of the two elements.

Effect of precursors on flavonoid production by Hydrocotyle ...

African Journals Online (AJOL)

Callus tissue of Hydrocotyle bonariensis was initiated from the leaf of H. bonariensis treated with 2 mg/l of 2,4-dichlorophenoxyacetic acid (2,4-D) and 1 mg/l kinetin. The culture was kept at 25°C, under light (cool white fluorescent tubes, 1200 lux). To optimize the precursors to increase the production of flavonoid, different ...

Synthesis of WO{sub 3} nanoparticles by citric acid-assisted precipitation and evaluation of their photocatalytic properties

Energy Technology Data Exchange (ETDEWEB)

Sánchez-Martínez, D. [Departamento de Ecomateriales y Energía, Facultad de Ingeniería Civil (UANL), Ciudad Universitaria, C.P. 66451, San Nicolás de los Garza, N.L. (Mexico); Martínez-de la Cruz, A., E-mail: azael70@yahoo.com.mx [Facultad de Ingeniería Mecánica y Eléctrica, Universidad Autónoma de Nuevo León, Ciudad Universitaria, C.P. 66451, San Nicolás de los Garza, N.L. (Mexico); López-Cuéllar, E. [Facultad de Ingeniería Mecánica y Eléctrica, Universidad Autónoma de Nuevo León, Ciudad Universitaria, C.P. 66451, San Nicolás de los Garza, N.L. (Mexico)

2013-02-15

Graphical abstract: Display Omitted Highlights: ► WO{sub 3} nanoparticles were synthesized by a simple citric acid-assisted precipitation. ► WO{sub 3} photocatalyst was able to the partial mineralization of rhB, IC and MO. ► WO{sub 3} can be considered as a photocatalyst active under visible light irradiation. -- Abstract: WO{sub 3} nanoparticles were synthesized by citric acid-assisted precipitation method using a 1:1.5 molar ratio of ammonium paratungstate hydrate (H{sub 42}N{sub 10}O{sub 42}W{sub 12}·xH{sub 2}O):citric acid (C{sub 6}H{sub 8}O{sub 7}). The formation of monoclinic crystal structure of WO{sub 3} at different temperatures was confirmed by X-ray powder diffraction (XRD). The characterization of the samples synthesized was complemented by transmission electron microscopy (TEM), Brunauer–Emmitt–Teller surface area (BET) and diffuse reflectance spectroscopy (DRS). According to the thermal treatment followed during the synthesis of WO{sub 3}, the morphology of the nanoparticles formed was characterized by rectangular and ovoid shapes. The photocatalytic activity of WO{sub 3} obtained under different experimental conditions was evaluated in the degradation of rhodamine B (rhB), indigo carmine (IC), methyl orange (MO), and Congo red (CR) in aqueous solution under UV and UV–vis radiation. The highest photocatalytic activity was observed in the sample obtained by thermal treatment at 700 °C. In general, the sequence of degradation of the organic dyes was: indigo carmine (IC) > rhodamine B (rhB) > methyl orange (MO) > Congo red (CR). The mineralization degree of organic dyes by WO{sub 3} photocatalysts was determined by total organic carbon analysis (TOC) reaching percentages of mineralization of 82% (rhB), 85% (IC), 28% (MO), and 7% (CR) for 96 h of lamp irradiation.

New Ir Bis-Carbonyl Precursor for Water Oxidation Catalysis

Energy Technology Data Exchange (ETDEWEB)

Huang, Daria L. [Department of Chemistry, Yale University, 225; Beltrán-Suito, Rodrigo [Department of Chemistry, Yale University, 225; Thomsen, Julianne M. [Department of Chemistry, Yale University, 225; Hashmi, Sara M. [Department of Chemical and Environmental; Materna, Kelly L. [Department of Chemistry, Yale University, 225; Sheehan, Stafford W. [Catalytic Innovations LLC, 70 Crandall; Mercado, Brandon Q. [Department of Chemistry, Yale University, 225; Brudvig, Gary W. [Department of Chemistry, Yale University, 225; Crabtree, Robert H. [Department of Chemistry, Yale University, 225

2016-02-05

This paper introduces IrI(CO)2(pyalc) (pyalc = (2-pyridyl)-2-propanoate) as an atom-efficient precursor for Ir-based homogeneous oxidation catalysis. This compound was chosen to simplify analysis of the water oxidation catalyst species formed by the previously reported Cp*IrIII(pyalc)OH water oxidation precatalyst. Here, we present a comparative study on the chemical and catalytic properties of these two precursors. Previous studies show that oxidative activation of Cp*Ir-based precursors with NaIO4 results in formation of a blue IrIV species. This activation is concomitant with the loss of the placeholder Cp* ligand which oxidatively degrades to form acetic acid, iodate, and other obligatory byproducts. The activation process requires substantial amounts of primary oxidant, and the degradation products complicate analysis of the resulting IrIV species. The species formed from oxidation of the Ir(CO)2(pyalc) precursor, on the other hand, lacks these degradation products (the CO ligands are easily lost upon oxidation) which allows for more detailed examination of the resulting Ir(pyalc) active species both catalytically and spectroscopically, although complete structural analysis is still elusive. Once Ir(CO)2(pyalc) is activated, the system requires acetic acid or acetate to prevent the formation of nanoparticles. Investigation of the activated bis-carbonyl complex also suggests several Ir(pyalc) isomers may exist in solution. By 1H NMR, activated Ir(CO)2(pyalc) has fewer isomers than activated Cp*Ir complexes, allowing for advanced characterization. Future research in this direction is expected to contribute to a better structural understanding of the active species. A diol crystallization agent was needed for the structure determination of 3.

Kinetic study on the acid-catalyzed hydrolysis of cellulose to levulinic acid

NARCIS (Netherlands)

Girisuta, B.; Janssen, L. P. B. M.; Heeres, H. J.

2007-01-01

A variety of interesting bulk chemicals is accessible by the acid-catalyzed hydrolysis of cellulose. An interesting example is levulinic acid, a versatile precursor for fuel additives, polymers, and resins. A detailed kinetic study on the acid-catalyzed hydrolysis of cellulose to levulinic acid is

[Characteristics of precipitation pH and conductivity at Mt. Huang].

Science.gov (United States)

Shi, Chun-e; Deng, Xue-liang; Wu, Bi-wen; Hong, Jie; Zhang, Su; Yang, Yuan-jian

2013-05-01

To understand the general characteristics of pH distribution and pollution in precipitation at Mt. Huang, statistical analyses were conducted for the routine measurements of pH and conductivity (K) at Mt. Huang during 2006-2011. The results showed that: (1) Over the period of study, the annual volume weighted mean (VWM) precipitation pH varied from 4.81 to 5.57, with precipitation acidity strengthening before 2009 and weakening thereafter. The precipitation acidity showed evident seasonal variations, with the VWM pH lowest in winter (4.78), and highest in summer (5.33). The occurrence frequency of acid rain was 46% , accounting for 45% of total rainfalls and with the most frequent pH falling into weak acid to neutral rain. (2) The annual VWM K varied from 16.91 to 27.84 microS x cm(-1), with no evident trend. As for ions pollution, the precipitation was relatively clean at Mt. Huang, with the most frequent K range being below 15 microS x cm(-1), followed by 15-25 microS x cm(-1). From February 2010 to December 2011, precipitation samples were collected on daily basis for ions analysis, as well as pH and K measurement in lab. Detailed comparisons were conducted between the two sets of pH and K, one set from field measurement and the other from lab measurement. The results indicated: (1) The lab measured pH (K) was highly correlated with the field pH (K); however, the lab pH tended to move towards neutral comparing with the corresponding field pH, and the shift range was closely correlated with the field pH and rainfall. The shift range of K from field to lab was highly correlated with the total ion concentration of precipitation. The field K showed evident negative correlation with the field pH with a correlation coefficient of -0.51. (2) When sampling with nylon-polyethylene bags, the statistics showed smaller bias between two sets of pH, with higher correlation coefficient between two sets of K. Furthermore, the lab K also showed evident negative correlation with

Three-decade changes in chemical composition of precipitation in Guangzhou city, southern China: has precipitation recovered from acidification following sulphur dioxide emission control?

Directory of Open Access Journals (Sweden)

Yunting Fang

2013-09-01

Full Text Available We examined if precipitation had recovered from acidification in Guangzhou, the third biggest city in China, and if sulphur deposition in precipitation had decreased, and to what extent if yes, following abatement strategies in sulphur dioxide (SO2 emission and energy use implemented since 2001. SO2 emissions were decreasing steadily since 2001, but a marked recovery of precipitation acidity occurred only since 2005; precipitation pH values decreased from 4.65 in 2001 to 4.34 in 2005 and then increased to 5.08 in 2010, while in the same period acid rain (pH<5.6 frequency increased from 70% to 81% and then decreased to 48%. During this period, the change in pH value and sulphate concentration more reflected the patterns of SO2 emission at provincial and national scales than at the local scale, suggesting that precipitation chemical composition was largely controlled by the emissions of pollutants from surrounding areas of the study city. Since 2001, sulphate deposition in precipitation decreased significantly (by 40% but nitrogen deposition remained unaltered. More importantly, the current sulphur (43 kg S ha−1 yr−1 as sulphate and nitrogen depositions (35 kg N ha−1 yr−1 as ammonium plus nitrate in 2010 were still among the highest in China. These results highlight the fact that ambient sulphur and nitrogen deposition still pose a threat to the health of both terrestrial and aquatic ecosystems. Precipitation may become more acidified in the future because the deposition of alkaline dusts containing calcium is also likely to decrease with stricter SO2 emission control policy and reduced construction activities. Additionally, we recommend that a reduction of emissions of nitrogen and chlorine bearing pollutants is urgently required for complete control on acid deposition.

Thermoset precursor

International Nuclear Information System (INIS)

Yamamoto, Y.

1983-04-01

This invention pertains to a distinctive thermoset precursor which is prepared by mixing a resin composition (A) which can be hardened by ionizing radiation, and a resin composition (B) which can be hardened by heat but cannot be hardened by, or is resistant to, ionizing radiation, and by coating or impregnating a molding or other substrate with a sheet or film of this mixture and irradiating this with an ionizing radiation. The principal components of composition (A) and (B) can be the following: (1) an acrylate or methacrylate and an epoxy resin and an epoxy resin hardener; (2) an unsaturated polyester resin and epoxy resin and an epoxy resin hardener; (3) a diacrylate or dimethacrylate or polyethylene glycol and an epoxy resin; (4) an epoxy acrylates or epoxy methacrylate obtained by the addition reaction of epoxy resin and acrylic or methacrylic acid

Fog and precipitation chemistry at a mid-land forest in central Taiwan.

Science.gov (United States)

Liang, Yang-Ling; Lin, Teng-Chiu; Hwong, Jeen-Liang; Lin, Neng-Huei; Wang, Chiao-Ping

2009-01-01

We analyzed fog and bulk precipitation chemistry at a cloud forest in central Taiwan where mountain agriculture activities are highest. There were 320 foggy days (visibility agriculture has a major impact on atmospheric deposition at the surrounding forest ecosystems. The input of inorganic N reached 125 kg N ha(-1) yr(-1) and likely exceeded the biological demand of the forest ecosystem. Sulfate is the most abundant anion in fog at Chi-tou and in precipitation at various forests throughout Taiwan, suggesting that the emission and transport of large quantities of SO(2,) the precursor of SO(4)(2-), is an island-wide environmental issue.

Precursor type affecting surface properties and catalytic activity of sulfated zirconia

Directory of Open Access Journals (Sweden)

Zarubica Aleksandra R.

2007-01-01

Full Text Available Zirconium-hydroxide precursor samples are synthesized from Zr-hydroxide, Zr-nitrate, and Zr-alkoxide, by precipitation/impregnation, as well as by a modified sol-gel method. Precursor samples are further sulphated for the intended SO4 2- content of 4 wt.%, and calcined at 500-700oC. Differences in precursors’ origin and calcination temperature induce the incorporation of SO4 2- groups into ZrO2 matrices by various mechanisms. As a result, different amounts of residual sulphates are coupled with other structural, as well as surface properties, resulting in various catalytic activities of sulphated zirconia samples. Catalyst activity and selectivity are a complex synergistic function of tetragonal phase fraction, sulphates contents, textural and surface characteristics. Superior activity of SZ of alkoxide origin can be explained by a beneficial effect of meso-pores owing to a better accommodation of coke deposits.

Pretreating dogwood seedlings with simulated acidic precipitation increases dogwood anthracnose symptoms in greenhouse-laboratory trials

Energy Technology Data Exchange (ETDEWEB)

Anderson, R.L.; Knighten, J. (USDA Forest Service, Resistance Screening Center, Asheville, NC (United States)); Berrange, P.; Lawton, K.A. (USDA Forest Service, Center for Forest Environmental Studies, Dry Branch, GA (United States)); Britton, K.O. (USDA Forest Service, Southeastern Forest Experiment Station, Athens, GA (United States))

1993-01-01

Dogwood anthracnose is the most damaging disease of flowering dogwood (Cornus florida L.) in a large part of the tree's natural range. It is caused by Discula destructiva infection. Previous attempts to inoculate C. florida to produce anthracnose symptoms have met with limited success except when the leaves were pretreated with acidic water, suggesting that acidic precipitation may predispose dogwoods to the disease. This hypothesis was tested in two greenhouse-laboratory studies in which year-old C. florida seedlings were randomly assigned to four treatments of simulated rain (pH 2.5, 3.5, 4.5, and 5.5) in 1989 and 1990. After 10 applications over a 42-d period, the seedlings were moved to a temperature-controlled laboratory, placed in plastic bags, humidified, and sprayed with a spore suspension of five D. destructiva isolates. About 30 d layter, the seedlings were examined for the percentage of leaves exhibiting anthracnose symptoms and disease severity on affected leaves. Both trials showed that as the acidity of the simulated rain increased, the incidence and severity of anthracnose leaf symptoms increased. The 1989 study included a soil lime treatment that showed the same trend but the overall occurrence and severity of symptoms was higher. 17 refs., 5 tabs.

Fabrication of ITO particles using a combination of a homogeneous precipitation method and a seeding technique and their electrical conductivity

Directory of Open Access Journals (Sweden)

Yoshio Kobayashi

2015-09-01

Full Text Available The present work proposes a method to fabricate indium tin oxide (ITO particles using precursor particles synthesized with a combination of a homogeneous precipitation method and a seeding technique, and it also describes their electronic conductivity properties. Seed nanoparticles were produced using a co-precipitation method with aqueous solutions of indium (III chloride, tin (IV chloride aqueous solution and sodium hydroxide. Three types of ITO nanoparticles were fabricated. The first type was fabricated using the co-precipitation method (c-ITO. The second and third types were fabricated using a homogeneous precipitation method with the seed nanoparticles (s-ITO and without seeds (n-ITO. The as-prepared precursor particles were annealed in air at 500 °C, and their crystal structures were cubic ITO. The c-ITO nanoparticles formed irregular-shaped agglomerates of nanoparticles. The n-ITO nanoparticles had a rectangular-parallelepiped or quasi-cubic structure. Most s-ITO nanoparticles had a quasi-cubic structure, and their size was larger than the n-ITO particles. The volume resistivities of the c-ITO, n-ITO and s-ITO powders decreased in that order because the regular-shaped particles were made to strongly contact with each other.

Sex pheromone in the moth Heliothis virescens is produced as a mixture of two pools: de novo and via precursor storage in glycerolipids.

Science.gov (United States)

Foster, Stephen P; Anderson, Karin G; Casas, Jérôme

2017-08-01

Most species of moths use a female-produced volatile sex pheromone, typically produced via de novo fatty acid synthesis in a specialized gland, for communication among mates. While de novo biosynthesis of pheromone (DNP) is rapid, suggesting transient precursor acids, substantial amounts of pheromone precursor (and other) acids are stored, predominantly in triacylglycerols in the pheromone gland. Whether these stored acids are converted to pheromone later or not has been the subject of some debate. Using a tracer/tracee approach, in which we fed female Heliothis virescens U- 13 C-glucose, we were able to distinguish two pools of pheromone, in which precursors were temporally separated (after and before feeding on labeled glucose): DNP synthesized from a mixed tracer/tracee acetyl CoA pool after feeding, and pheromone made from precursor acids primarily synthesized before feeding, which we call recycled precursor fat pheromone (RPP). DNP titer varied from high (during scotophase) to low (photophase) and with presence/absence of pheromone biosynthesis activating neuropeptide (PBAN), in accord with native pheromone titer previously observed. By contrast, RPP was constant throughout the photoperiod and did not change with PBAN presence/absence. The amount of RPP (6.3-10.3 ng/female) was typically much lower than that of DNP, especially during the scotophase (peak DNP, 105 ng/female). We propose an integral role for stored fats in pheromone biosynthesis, in which they are hydrolyzed and re-esterified throughout the photoperiod, with a small proportion of liberated precursor acyl CoAs being converted to pheromone. During the sexually active period, release of PBAN results in increased flux of glucose (from trehalose) and hydrolyzed acids entering the mitochondria, producing acetyl CoA precursor for de novo fat and pheromone biosynthesis. Copyright © 2017 Elsevier Ltd. All rights reserved.

A perspective of stepwise utilisation of Bayer red mud: Step two--Extracting and recovering Ti from Ti-enriched tailing with acid leaching and precipitate flotation.

Science.gov (United States)

Huang, Yanfang; Chai, Wencui; Han, Guihong; Wang, Wenjuan; Yang, Shuzhen; Liu, Jiongtian

2016-04-15

The extraction and recovery of Ti from Ti-enriched tailing with acid leaching and precipitate flotation, as one of the critical steps, was proposed for the stepwise utilization of red mud. The factors influencing acid leaching and precipitate flotation were examined by factorial design. The leaching thermodynamics, kinetics of Ti(4+), Al(3+) and Fe(3+), and the mechanism of selectively Fe(3+) removal using [Hbet][Tf2N] as precipitating reagent were discussed. The extracting of Ti(4+), Al(3+) and Fe(3+) in concentrated H2SO4 is controlled by diffusion reactions, depending mainly upon leaching time and temperature. The maximum extracting efficiency of Ti(4+) is approximately 92.3%, whereas Al(3+) and Fe(3+) leaching are respectively 75.8% and 84.2%. [Hbet][Tf2N], as a precipitating reagent, operates through a coordination mechanism in flotation. The pH value is the key factor influencing the flotation recovery of Ti(4+), whereas the dosage of precipitating reagent is that for Al(3+) recovery. The maximum flotation recovery of Ti(4+) is 92.7%, whereas the maximum Al(3+) recovery is 93.5%. The total recovery rate for extracting and recovering titanium is 85.5%. The liquor with Ti(4+) of 15.5g/L, Al(3+) of 30.4g/L and Fe(3+) of 0.48g/L was obtained for the following hydrolysis step in the integrated process for red mud utilisation. Copyright © 2016 Elsevier B.V. All rights reserved.

Uranium peroxide precipitate drying temperature relationships

Energy Technology Data Exchange (ETDEWEB)

Rodgers, C.; Dyck, B., E-mail: chick_rodgers@cameco.com [Cameco Corp., Saskatoon, SK (Canada)

2010-07-01

Cameco Corporation is in the process of revitalizing the mill at its Key Lake operation in northern Saskatchewan. The current Key Lake process employs ammonia stripping and ammonia precipitation. As part of the revitalization, the company is considering installing strong acid stripping in solvent extraction as used at its Rabbit Lake operation. This change would lead to using hydrogen peroxide for uranium precipitation. As part of the process evaluation, tests were carried out to study how changes in the temperature of an indirect fired dryer affected the properties of uranium peroxide [yellowcake] precipitate. This paper discusses the results of the test work, including the relationships between drying temperature and the following: (author)

Precipitation of plutonium (III) oxalate and calcination to plutonium oxide

International Nuclear Information System (INIS)

Esteban, A.; Orosco, E.H.; Cassaniti, P.; Greco, L.; Adelfang, P.

1989-01-01

The plutonium based fuel fabrication requires the conversion of the plutonium nitrate solution from nuclear fuel reprocessing into pure PuO2. The conversion method based on the precipitation of plutonium (III) oxalate and subsequent calcination has been studied in detail. In this procedure, plutonium (III) oxalate is precipitated, at room temperature, by the slow addition of 1M oxalic acid to the feed solution, containing from 5-100 g/l of plutonium in 1M nitric acid. Before precipitation, the plutonium is adjusted to trivalent state by addition of 1M ascorbic acid in the presence of an oxidation inhibitor such as hydrazine. Finally, the precipitate is calcinated at 700 deg C to obtain PuO2. A flowsheet is proposed in this paper including: a) A study about the conditions to adjust the plutonium valence. b) Solubility data of plutonium (III) oxalate and measurements of plutonium losses to the filtrate and wash solution. c) Characterization of the obtained products. Plutonium (III) oxalate has several potential advantages over similar conversion processes. These include: 1) Formation of small particle sizes powder with good pellets fabrication characteristics. 2) The process is rather insensitive to most process variables, except nitric acid concentration. 3) Ambient temperature operations. 4) The losses of plutonium to the filtrate are less than in other conversion processes. (Author) [es

Experimental evidence on formation of imminent and short-term hydrochemical precursors for earthquakes

International Nuclear Information System (INIS)

Du Jianguo; Amita, Kazuhiro; Ohsawa, Shinji; Zhang Youlian; Kang Chunli; Yamada, Makoto

2010-01-01

The formation of imminent hydrochemical precursors of earthquakes is investigated by the simulation for water-rock reaction in a brittle aquifer. Sixty-one soaking experiments were carried out with granodiorite and trachyandesite grains of different sizes and three chemically-distinct waters for 6 to 168 h. The experimental data demonstrate that water-rock reaction can result in both measurable increases and decreases of ion concentrations in short times and that the extents of hydrochemical variations are controlled by the grain size, dissolution and secondary mineral precipitation, as well as the chemistry of the rock and groundwater. The results indicate that water-rock reactions in brittle aquifers and aquitards may be an important genetic mechanism of hydrochemical seismic precursors when the aquifers and aquitards are fractured in response to tectonic stress.

Comparative study on precipitation methods of yellow-cake from acid leachate of rock phosphate and Its purification

International Nuclear Information System (INIS)

Abow Slama, E. H. Y.

2009-05-01

This study was carried-out to leach uranium from rock phosphate using sulphuric acid in presences of potassium chlorate as an oxidant and to investigate the relative purity of different forms of yellow cakes produced with ammonia ((NH 4 ) 2 U 2 O 7 ), magnesia (UO 3 .xH 2 O) and sodium hydroxide (Na 2 U 2 O 7 ) as precipitants, as well as purification of the products with TBP extraction and matching its impurity levels with specification of the commercial products. Alpha-particle spectrometry was for used for determination of activity concentration of uranium isotopes (''2''3''4U and ''2''3''8U) in rock phosphate, resulting green phosphoric acid solution, and in different forms of the yellow cake from which the equivalent mass concentration of uranium was deduced. Likewise, AAS was used for determination of impurities (Pb, Ni, Cd, Fe, Zn, Mn, and Cu). On the average, the activity concentration of uranium in the rock phosphate was 1468±979 Bq/Kg (119.38±79.66 ppm), and 711±252 Bq/L (57.85±20.46 ppm) in the resulting green solution with corresponding percent of dissolution amounting to 48% which is considered low indicating that the experimental conditions (i.e. dissolution container, temperature, PH, retention time) were not optimal. However, the isotopic ratio (''2''3''4U, ''2''3''8U) in all stages of hydrometallurgical process was not much different from unity indicating lack of fractionation. Crude yellow cakes (hydrate uranium trioxide, ammonium diuranate and sodium diuranate) were precipitated from the green solutions prior to separation of iron and once after iron separation. Although, iron was tested using bipyridine and SCN, it was found in all types of crude samples analyzed this might be attributed to either the quality of the reagent used or inhibition of Fe present in the solution by stronger complexing agent. Uranium mass concentration in crude yellow cakes precipitated before iron separation was found following the order: UO 3 .xH 2 O

Ionospheric earthquake precursors

International Nuclear Information System (INIS)

Bulachenko, A.L.; Oraevskij, V.N.; Pokhotelov, O.A.; Sorokin, V.N.; Strakhov, V.N.; Chmyrev, V.M.

1996-01-01

Results of experimental study on ionospheric earthquake precursors, program development on processes in the earthquake focus and physical mechanisms of formation of various type precursors are considered. Composition of experimental cosmic system for earthquake precursors monitoring is determined. 36 refs., 5 figs

Synthesis and characterization of a boron-containing precursor for ZrB{sub 2} ceramic

Energy Technology Data Exchange (ETDEWEB)

Tao, X.Y.; Xiang, Z.; Zhou, S.; Zhu, Y. [China Univ. of Mining and Technology, Xuzhou (China). School of Materials Science and Engineering; Qiu, W.; Zhao, T. [Chinese Academy of Sciences, Beijing (China). Lab. of Advanced Polymer Materials

2016-07-01

A precursor for ZrB{sub 2} ceramic was successfully synthesized in a chemical reaction between polyzirconoxanesal (PZS) and boric acid. The molecular structure of the precursor, thermal properties and the pyrolysis behavior of the precursor were investigated. The results showed that the as-synthesized precursor was a polymer based on Zr-O-C-B bonds. The precursor was stable in air atmosphere and soluble in common organic solvents. The ceramic yield of the precursor at 1200 C was around 65.5 % under N{sub 2} atmosphere. The derived ceramics obtained at 1200 C were composed of B{sub 2}O{sub 3}, ZrO{sub 2} and carbon. When the temperature was increased up to 1300 C, peaks of ZrC emerged owing to carbothermal reduction. m-ZrO{sub 2} and t-ZrO{sub 2} disappeared when the pyrolysis temperature was increased to above 1400 C. ZrB{sub 2} became the predominant phase when the pyrolysis temperature was increased up to 1500 C.

The precipitation and effect of nano nitrides in HSLC steel

Institute of Scientific and Technical Information of China (English)

2008-01-01

The existing forms of N and Al in HSLC (high strength low carbon) steel produced by TSCR (thin slab casting and rolling process), the precipitation thermodynamics and kinetics of AlN, and its effects on structure and mechanical property are studied. The experimental results show that only a small quantity of nitrogen is com- bined into AlN in HSLC steel produced by TSCR and most of the nitrogen in steel is still free nitrogen. Aluminum-nitride is mainly precipitated during the period of slow air cooling after coiling, but not during rolling and water cooling. The acid-soluble aluminum has no obvious effect on the grain size and mechanical property of HSLC steel produced by TSCR whose acid-soluble aluminum content is 0.005%―0.043%. The precipitation of AlN is not the main cause of grain refinement of HSLC steel produced by TSCR, nor is AlN the dominating precipitate that has precipitation strengthening effect. The nano nitrides are not pure AlN, but have complex compositions.

A simple procedure for preparing chitin oligomers through acetone precipitation after hydrolysis in concentrated hydrochloric acid.

Science.gov (United States)

Kazami, Nao; Sakaguchi, Masayoshi; Mizutani, Daisuke; Masuda, Tatsuhiko; Wakita, Satoshi; Oyama, Fumitaka; Kawakita, Masao; Sugahara, Yasusato

2015-11-05

Chitin oligomers are of interest because of their numerous biologically relevant properties. To prepare chitin oligomers containing 4-6 GlcNAc units [(GlcNAc)4-6], α- and β-chitin were hydrolyzed with concentrated hydrochloric acid at 40 °C. The reactant was mixed with acetone to recover the acetone-insoluble material, and (GlcNAc)4-6 was efficiently recovered after subsequent water extraction. Composition analysis using gel permeation chromatography and MALDI-TOF mass spectrometry indicated that (GlcNAc)4-6 could be isolated from the acetone-insoluble material with recoveries of approximately 17% and 21% from the starting α-chitin and β-chitin, respectively. The acetone precipitation method is highly useful for recovering chitin oligomers from the acid hydrolysate of chitin. The changes in the molecular size and higher-order structure of chitin during the course of hydrolysis were also analyzed, and a model that explains the process of oligomer accumulation is proposed. Copyright © 2015 Elsevier Ltd. All rights reserved.

Optimization of the Hydrolysis of Safflower Oil for the Production of Linoleic Acid, Used as Flavor Precursor

Directory of Open Access Journals (Sweden)

Marya Aziz

2015-01-01

Full Text Available Commercial lipases, from porcine pancreas (PPL, Candida rugosa (CRL, and Thermomyces lanuginosus (Lipozyme TL IM, were investigated in terms of their efficiency for the hydrolysis of safflower oil (SO for the liberation of free linoleic acid (LA, used as a flavor precursor. Although PPL, under the optimized conditions, showed a high degree of hydrolysis (91.6%, its low tolerance towards higher substrate concentrations could limit its use for SO hydrolysis. In comparison to the other investigated lipases, Lipozyme TL IM required higher amount of enzyme and an additional 3 h of reaction time to achieve its maximum degree of SO hydrolysis (90.2%. On the basis of the experimental findings, CRL was selected as the most appropriate biocatalyst, with 84.1% degree of hydrolysis. The chromatographic analyses showed that the CRL-hydrolyzed SO is composed mainly of free LA.

Optimization of the Hydrolysis of Safflower Oil for the Production of Linoleic Acid, Used as Flavor Precursor.

Science.gov (United States)

Aziz, Marya; Husson, Florence; Kermasha, Selim

2015-01-01

Commercial lipases, from porcine pancreas (PPL), Candida rugosa (CRL), and Thermomyces lanuginosus (Lipozyme TL IM), were investigated in terms of their efficiency for the hydrolysis of safflower oil (SO) for the liberation of free linoleic acid (LA), used as a flavor precursor. Although PPL, under the optimized conditions, showed a high degree of hydrolysis (91.6%), its low tolerance towards higher substrate concentrations could limit its use for SO hydrolysis. In comparison to the other investigated lipases, Lipozyme TL IM required higher amount of enzyme and an additional 3 h of reaction time to achieve its maximum degree of SO hydrolysis (90.2%). On the basis of the experimental findings, CRL was selected as the most appropriate biocatalyst, with 84.1% degree of hydrolysis. The chromatographic analyses showed that the CRL-hydrolyzed SO is composed mainly of free LA.

A review on the kinetics of microbially induced calcium carbonate precipitation by urea hydrolysis

Science.gov (United States)

van Paassen, L. A.

2017-12-01

In this study the kinetics of calcium carbonate precipitation induced by the ureolytic bacteria are reviewed based on experiments and mathematical modelling. The study shows how urea hydrolysis rate depends on the amount of bacteria and the conditions during growth, storage, hydrolysis and precipitation. The dynamics of Microbially Induced Carbonate Precipitation has been monitored in non-seeded liquid batch experiments. Results show that particulary for a fast hydrolysis of urea (>1 M-urea day-1) in a highly concentrated equimolar solution with calcium chloride (>0.25 M) the solubility product of CaCO3 is exceeded within a short period (less than 30 minutes), the supersaturation remains high for an exended period, resulting in prolonged periods of nucleation and crystal growth and extended growth of metastable precursor mineral phases. The pH, being a result of the speciation, quickly rises until critical supersaturation is reached and precipitation is initiated. Then pH drops (sometimes showing oscillating behaviour) to about neutral where it stays until all substrates are depleted. Higher hydrolysis rates lead to higher supersaturation and pH and relatively many small crystals, whereas higher concentrations of urea and calcium chloride mainly lead to lower pH values. The conversion can be reasonably monitored by electrical conductivity and reasonably predicted, using a simplified model based on a single reaction as long as the urea hydrolysis rate is known. Complex geochemical models, which include chemical speciciation through acid-base equilibria and kinetic equations to describe mineral precipitation, do not show significant difference from the simplified model regarding the bulk chemistry and the total amount of precipitates. However, experiments show that ureolytic MICP can result in a highly variable crystal morphologies with large variation in the affected hydraulic properties when applied in a porous medium. In order to calculate the number, size and

Preparation and Characterization of Various Activated Carbons Derived From Mixed Precursors Using Phosphoric Acid

International Nuclear Information System (INIS)

Daifullah, A.A.M.; Sharaf El-Deen, S.E.A.; Elkhalafawy, A.; Shehata, F.A.; Mahmoud, W.H.

2008-01-01

Rice straw (RS) and rice husk (RH), a low-cost agricultural by-products, have been used as a mixed precursor (i.e., RS mixed with RH in 1:1; 1:3 and 3:1 ratios) for the production of novel carbons using phosphoric acid as chemical activation. The raw materials were impregnated with 50% and 70% H 3 PO 4 followed by activation at 500 degree C. The latter proved to be the most effective in producing active carbon with good adsorptive capacity. The resulting carbons were characterized by elemental analysis, infrared spectroscopy, density, SEM and S BET . In general, the resulting carbons showed reasonable surface areas with mainly micropore structure. The adsorption capacity was demonstrated by the isotherms of methylene blue (MB), phenol and iodine from aqueous solution. The adsorption data was found to conform with the Langmuir equation with the concentration range studied, and the monolayer coverage was determined for each of the samples. It was found that surface area is mainly attributed to micropore volume so that phenol adsorption and iodine number correspond well with surface area determined by nitrogen adsorption

Analysis of ADU structure obtained under different precipitation conditions

International Nuclear Information System (INIS)

Ramella, Jose L.; Esteban, Adolfo; Mendez De Leo, Lucia P.; Sassone, Ariel; Novara, Oscar E.; Boero, Norma L.; Leyva, Ana G.

1999-01-01

ADU is the nominal name for ammonium poly uranate. It is a very complex compound of polymeric structure, which may have, according to precipitation conditions, different chemical composition and crystallographic structure. ADU is used as uranium oxide precursor in the manufacture of fuel elements. In former papers it was proved that if ultrasound is applied during precipitation and digestion the characteristics of the final product (U 3 O 8 UO 2 ) improve. By studying ADU thermal decomposition obtained by ultrasonic application, it was intended to obtain its composition. Therefore, differential thermal gravimetric and differential thermal analyses were performed. Samples were taken from special points and analyzed by X-ray diffraction, infra-red spectroscopy and scanning. An experiment was also designed to identify the products released during heating. Results and conclusions obtained are presented in this work. (author)

Organophosphonic acid as precursor to prepare LiFePO4/carbon nanocomposites for high-power lithium ion batteries

International Nuclear Information System (INIS)

Chen, Ming; Shao, Leng-Leng; Yang, Hua-Bin; Zhao, Qian-Yong; Yuan, Zhong-Yong

2015-01-01

Graphical abstract: LiFePO4/C nanocomposites were prepared by a quasi-sol–gel method with the use of organophosphonic acid, exhibiting improved electrochemical performance with excellent cycle stability. Display Omitted -- Highlights: •Amino tris(methylene phosphonic acid) is served as a novel precursor for LiFePO 4 /C. •Nano-sized and high-purity LiFePO 4 /C composites are obtained by a quasi-sol–gel route. •Core-shell structured LiFePO 4 /C nanocomposites are fabricated by further introducing sucrose. •Superior electrochemical performance is observed in the organophosphorus-synthesized LiFePO 4 /C. -- Abstract: Amino tris(methylene phosphonic acid) (ATMP) is selected as phosphorus and carbon co-source for the synthesis of uniformly nano-sized LiFePO 4 /C by a quasi-sol–gel method. This strategy using ATMP instead of conventional NH 4 H 2 PO 4 supplies two advantages: firstly, ATMP in situ chelates Li + onto its framework and subsequently binds with FeC 2 O 4 in aqueous solution, forming a molecule-scale homogeneous precursor which can obviously improve the purity of LiFePO 4 . Secondly, the organic carbon contained in ATMP can form uniformly distributed conductive carbon networks among LiFePO 4 particles after calcination, which improves the electrical conductivity. The resultant LiFePO 4 /C with 1.1 wt.% carbon achieves a higher discharge capacity than those of LiFePO 4 and LiFePO 4 /C prepared with inorganic NH 4 H 2 PO 4 . Moreover, core-shell structured LiFePO 4 /C nanocomposites are also fabricated by further introducing sucrose into the synthesis system. The high-quality carbon shell effectively hinders the LiFePO 4 particle growth and aggregation under high-temperature treatment, which further enhances the electrical conductivity and lithium-ion diffusion, resulting in the improved electrochemical performance with excellent cycle stability (the optimum discharge capacity of 158.6 mAh g −1 at 0.1 C and 138.4 mAh g −1 at 2 C). The high

Optimization of the conditions for the precipitation of thorium oxalate. II. Minimization of the product losses

International Nuclear Information System (INIS)

Pazukhin, E.M.; Smirnova, E.A.; Krivokhatskii, A.S.; Pazukhina, Yu.L.; Kiselev, P.P.

1987-01-01

The precipitation of thorium as a poorly soluble oxalate was investigated. An equation relating the concentrations of the metal and nitric acid in the initial solution and the amount of precipitant required to minimize the product losses was derived. A graphical solution of the equation is presented for the case where the precipitant is oxalic acid at a concentration of 0.78 M

Seasonal variations of ochreous precipitates in mine effluents in Finland

International Nuclear Information System (INIS)

Kumpulainen, Sirpa; Carlson, Liisa; Raeisaenen, Marja-Liisa

2007-01-01

Ochreous precipitate and water samples were collected from the surroundings of seven closed sulphide mines in Finland. In the Hammaslahti Zn-Cu-Au mine, Otravaara pyrite mine and Paroistenjaervi Cu-W-As mine, the collection was repeated in different seasons to study mineralogical and geochemical variations of precipitates. The sampling was done in 1999-2002 from the ditches and drainage ponds of the tailings and waste rock piles that are susceptible to seasonal changes. Mineralogy of the precipitates was evaluated by X-ray diffraction (XRD) and infrared spectroscopy (IR), and precipitate geochemistry was examined by selective extractions. Schwertmannite (Fe 8 O 8 (OH) 6 SO 4 ) was the most typical Fe hydroxide mineral found. Goethite was almost as common as schwertmannite, was often poorly ordered, and contained up to 10 wt.% of SO 4 . Goethite and schwertmannite were commonly found as mixtures, and they occurred in similar pH and SO 4 concentrations. Ferrihydrite (nominally Fe 5 HO 8 . 4H 2 O) was typically found in areas not influenced by acid mine drainage, and also in acid mine waters with high organic matter or As content. Jarosite (KFe 3 (SO 4 ) 2 (OH) 6 ) was found only in one site. In addition, some gypsum (CaSO 4 . 2H 2 O) and aluminous sulphate precipitates (presumably basaluminite, Al 4 (SO 4 )(OH) 10 . 5H 2 O) were identified. Selective extractions showed that acid extracts Fe tot /S tot -ratios of schwertmannite and goethite samples were similar, but the ratio of oxalate-extractable to total Fe, Fe ox /Fe tot , of goethite samples were lower than those of the schwertmannite samples. Only Al, Si and As were bound to precipitates in substantial amounts, up to several wt.%. In schwertmannites and goethites, Al, Cu, Co, Mn and Zn were mostly structural, substituting for Fe in an Fe oxyhydroxide structure or bound to surface adsorption sites in pores limited by diffusion. In ferrihydrites, heavy metals were also partly bound in adsorbed form dissolving in

Study on the Key Technology of High Purity Strontium Titanate Powder Synthesized from Oxalic Acid Co-sediment Precipitation

Science.gov (United States)

Bi, Xiaoguo; Dong, Yingnan; Li, Yingjie; Niu, Wei; Tang, Jian; Ding, Shuang; Li, Meiyang

2017-09-01

Oxalate coprecipitation is applied in this paper, high purity titanium tetrachloride, and after the purification of strontium chloride, match with a certain concentration of solution, oxalate and strontium chloride and titanium tetrachloride in 1.005:1.000 make strontium titanium mixture ratio, slowly under 60°C to join in oxalic acid solution, aging around 4 h, get oxygen titanium strontium oxalate (SrTiO(C2O4)2 • 4H2 ) precipitation, after washing, drying and other process made oxygen titanium strontium oxalate powder.

Methods for conversion of lignocellulosic-derived products to transportation fuel precursors

Science.gov (United States)

Lilga, Michael A.; Padmaperuma, Asanga B.

2017-10-03

Methods are disclosed for converting a biomass-derived product containing levulinic acid and/or gamma-valerolactone to a transportation fuel precursor product containing diesel like hydrocarbons. These methods are expected to produce fuel products at a reduced cost relative to conventional approaches.

Preparation of macroporous zirconia monoliths from ionic precursors via an epoxide-mediated sol-gel process accompanied by phase separation

International Nuclear Information System (INIS)

Guo, Xingzhong; Song, Jie; Lvlin, Yixiu; Yang, Hui; Nakanishi, Kazuki; Kanamori, Kazuyoshi

2015-01-01

Monolithic macroporous zirconia (ZrO 2 ) derived from ionic precursors has been successfully fabricated via the epoxide-mediated sol-gel route accompanied by phase separation in the presence of propylene oxide (PO) and poly(ethylene oxide) (PEO). The addition of PO used as an acid scavenger mediates the gelation, whereas PEO enhances the polymerization-induced phase separation. The appropriate choice of the starting compositions allows the production of a macroporous zirconia monolith with a porosity of 52.9% and a Brunauer–Emmett–Teller (BET) surface area of 171.9 m 2 · g −1 . The resultant dried gel is amorphous, whereas tetragonal ZrO 2 and monoclinic ZrO 2 are precipitated at 400 and 600 °C, respectively, without spoiling the macroporous morphology. After solvothermal treatment with an ethanol solution of ammonia, tetragonal ZrO 2 monoliths with smooth skeletons and well-defined mesopores can be obtained, and the BET surface area is enhanced to 583.8 m 2 · g −1 . (paper)

GAS-PHASE SYNTHESIS OF PRECURSORS OF INTERSTELLAR GLYCINE: A COMPUTATIONAL STUDY OF THE REACTIONS OF ACETIC ACID WITH HYDROXYLAMINE AND ITS IONIZED AND PROTONATED DERIVATIVES

Energy Technology Data Exchange (ETDEWEB)

Barrientos, Carmen; Redondo, Pilar; Largo, Laura; Rayon, Victor M.; Largo, Antonio, E-mail: alargo@qf.uva.es [Departamento de Quimica Fisica y Quimica Inorganica, Facultad de Ciencias, Universidad de Valladolid, 47005 Valladolid (Spain)

2012-04-01

A computational study of the reactions of hydroxylamine and its ionized and protonated derivatives with acetic acid is provided. The reaction of neutral hydroxylamine with acetic acid, despite being clearly exothermic, involves a very large energy barrier. The reaction of ionized hydroxylamine with acetic acid is also clearly exothermic, but again a significant energy barrier is found (around 24 kcal mol{sup -1} at the CCSD(T) level). The reaction of the most stable protonated isomer of hydroxylamine, NH{sub 3}OH{sup +}, with acetic acid also involves a high barrier (more than 27 kcal mol{sup -1} at the CCSD(T) level). Only the higher energy isomer, NH{sub 2}OH{sup +}{sub 2}, leads to a sensibly lower energy barrier (about 2.3 kcal mol{sup -1} at the CCSD(T) level). Nevertheless, an estimate of the reaction coefficient at low temperatures such as those reigning in the interstellar medium gives very low values. Therefore, it seems that precursors of interstellar glycine could not be efficiently produced from the reactions of hydroxylamine-derived ions with acetic acid.

GAS-PHASE SYNTHESIS OF PRECURSORS OF INTERSTELLAR GLYCINE: A COMPUTATIONAL STUDY OF THE REACTIONS OF ACETIC ACID WITH HYDROXYLAMINE AND ITS IONIZED AND PROTONATED DERIVATIVES

International Nuclear Information System (INIS)

Barrientos, Carmen; Redondo, Pilar; Largo, Laura; Rayón, Víctor M.; Largo, Antonio

2012-01-01

A computational study of the reactions of hydroxylamine and its ionized and protonated derivatives with acetic acid is provided. The reaction of neutral hydroxylamine with acetic acid, despite being clearly exothermic, involves a very large energy barrier. The reaction of ionized hydroxylamine with acetic acid is also clearly exothermic, but again a significant energy barrier is found (around 24 kcal mol –1 at the CCSD(T) level). The reaction of the most stable protonated isomer of hydroxylamine, NH 3 OH + , with acetic acid also involves a high barrier (more than 27 kcal mol –1 at the CCSD(T) level). Only the higher energy isomer, NH 2 OH + 2 , leads to a sensibly lower energy barrier (about 2.3 kcal mol –1 at the CCSD(T) level). Nevertheless, an estimate of the reaction coefficient at low temperatures such as those reigning in the interstellar medium gives very low values. Therefore, it seems that precursors of interstellar glycine could not be efficiently produced from the reactions of hydroxylamine-derived ions with acetic acid.

Synthesis of Nanoparticles of the Giant Dielectric Material, CaCu3Ti4O12 from a Precursor Route

OpenAIRE

Thomas, P.; Dwarakanath, K.; Varma, K. B. R.; Kutty, T. R. N.

2013-01-01

A complex oxalate precursor, CaCu3(TiO)4(C2O4)8.9H2O, was synthesized and the precipitate that obtained was confirmed to be monophasic by the wet chemical analyses, X-ray diffraction, FTIR absorption and TG, DTA analyses. The thermal decomposition of this oxalate precursor led to the formation of phase-pure calcium copper titanate, CaCu3Ti4O12, at 680oC. The bright field TEM micrographs revealed that the size of the as synthesized crystallites to be in the 30 to 80 nm range. The powders so ob...

Synthesis of CuO-NiO core-shell nanoparticles by homogeneous precipitation method

International Nuclear Information System (INIS)

Bayal, Nisha; Jeevanandam, P.

2012-01-01

Highlights: ► CuO-NiO core-shell nanoparticles have been synthesized using a simple homogeneous precipitation method for the first time. ► Mechanism of the formation of core-shell nanoparticles has been investigated. ► The synthesis route may be extended for the synthesis of other mixed metal oxide core-shell nanoparticles. - Abstract: Core-shell CuO–NiO mixed metal oxide nanoparticles in which CuO is the core and NiO is the shell have been successfully synthesized using homogeneous precipitation method. This is a simple synthetic method which produces first a layered double hydroxide precursor with core-shell morphology which on calcination at 350 °C yields the mixed metal oxide nanoparticles with the retention of core-shell morphology. The CuO–NiO mixed metal oxide precursor and the core-shell nanoparticles were characterized by powder X-ray diffraction, FT-IR spectroscopy, thermal gravimetric analysis, elemental analysis, scanning electron microscopy, transmission electron microscopy, and diffuse reflectance spectroscopy. The chemical reactivity of the core-shell nanoparticles was tested using catalytic reduction of 4-nitrophenol with NaBH 4 . The possible growth mechanism of the particles with core-shell morphology has also been investigated.

Marine bacterial transparent exopolymer particles (TEP) and TEP precursors: Characterization and RO fouling potential

KAUST Repository

Li, Sheng

2015-10-31

This paper investigated the characteristics and membrane fouling potential of bacterial transparent exopolymer particles (TEP)/TEP precursors released from two marine bacteria, Pseudidiomarina homiensis (P. homiensis) and Pseudoalteromonas atlantica (P. atlantica), isolated from the Red Sea. Results showed that both bacteria grew at the similar rate, but the production of TEP/TEP precursors from P. atlantica was higher than that from P. homiensis. During the 168. h of incubation time, production rates of TEP/TEP precursors from P. atlantica and P. homiensis were 0.30 and 0.08 xanthan gum eq. mg/L-h, respectively. Isolated bacterial TEP precursors were mainly biopolymer, and P. atlantica produced a significantly higher concentration of biopolymer than that produced by P. homiensis. TEP/TEP precursors from both marine bacteria possessed protein-like material and were very similar in composition to previously reported foulants isolated from a fouled reverse osmosis (RO) membrane. Bacterial TEP/TEP precursors mostly consisted of aliphatic hydrocarbon from amino acids and amide group carbon of proteins (around 55%). Bacterial TEP precursors caused obvious fouling on RO membranes, which may create an ideal environment for bacteria attachment and promote to biofouling.

Study of fallout by precipitation around an oil-fired power plant

Energy Technology Data Exchange (ETDEWEB)

Granat, L; Rodhe, H

1973-01-01

An investigation into the distribution of deposition by precipitation around an oil-fired power plant on the west coast of Sweden is presented. The measurements cover seven precipitation events during late fall. The samples have been analyzed for sulfur, pH, alkalinity, and sodium. In most precipitation events an additional deposition (above the regional background level) of sulfur and acid has been identified on the leeward side of the source. Compared with the background values, the observed increase was generally less than about 100 percent. As a long-term average the additional deposition of acid by precipitation, due to the power plant, is estimated to be not larger than 10-15 percent within 15 km of the plant. A comparison with emitted quantities shows that 1-6 percent of the sulfur emittted during the precipitation has been deposited within the first 15 km, corresponding to a travel time of 20-60 min. If the comparison is made using the total emission, including the dry periods, this fraction is only a few per mille.

Effect of Aqueous Media on the Recovery of Scandium by Selective Precipitation

Directory of Open Access Journals (Sweden)

Bengi Yagmurlu

2018-05-01

Full Text Available This research presents a novel precipitation method for scandium (Sc concentrate refining from bauxite residue leachates and the effect of aqueous media on this triple-stage successive precipitation process. The precipitation pattern and the precipitation behavior of the constituent elements was investigated using different precipitation agents in three major mineral acid media, namely, H2SO4, HNO3, and HCl in a comparative manner. Experimental investigations showed behavioral similarities between HNO3 and HCl media, while H2SO4 media was different from them because of the nature of the formed complexes. NH4OH was found to be the best precipitation agent in every leaching media to remove Fe(III with low Sc co-precipitation. To limit Sc loss from the system, Fe(III removal was divided into two steps, leading to more than 90% of Fe(III removal at the end of the process. Phosphate concentrates were produced in the final step of the precipitation process with dibasic phosphates which have a strong affinity towards Sc. Concentrates containing more than 50% of ScPO4 were produced in each case from the solutions after Fe(III removal, as described. A flow diagram of the selective precipitation process is proposed for these three mineral acid media with their characteristic parameters.

Microbially Induced Precipitation of Gold(0) Nanoparticles.

Science.gov (United States)

Roh, Yu; Kang, Serku; Park, Bitna; Kim, Yumi

2015-01-01

The objectives of this study were to synthesize gold nanoparticles by biomineralization using metal-reducing bacteria and to characterize their mineralogical properties. The metal-reducing bacteria were able to reduce Au(III) to Au(0) with organic fatty acids as electron donors, as indicated by the color change of the culture solution from colorless gold ions to black precipitates at 25 degrees C. XRD, SEM- and TEM-EDS analyses of the precipitates showed that Au(0) was precipitated and formed at either the cell membrane or extracellularly. The Au(0) nanoparticles were about 200 nm in size and ball-shaped. Biomineralization for elemental Au(0) nanoparticle synthesis may be useful for the recovery of natural gold in natural environments.

Powder of a copper oxide superconductor precursor, fabrication process and use for the preparation of superconducting oxide

International Nuclear Information System (INIS)

Dehaudt, P.

1990-01-01

The precursor powder comprises at least a copper compound (hydroxide, oxide and hydroxynitrates), at least a rare earth and/or yttrium compound (nitrates, hydroxides and hydroxynitrates) or bismuth oxide and at least an alkaline earth nitrate. It can be prepared by atomization drying of a suspension a copper precipitate or coprecipitate and other elements of the superconducting oxide in solution [fr

Towards deriving Ni-rich cathode and oxide-based anode materials from hydroxides by sharing a facile co-precipitation method.

Science.gov (United States)

Qiu, Haifa; Du, Tengfei; Wu, Junfeng; Wang, Yonglong; Liu, Jian; Ye, Shihai; Liu, Sheng

2018-05-22

Although intensive studies have been conducted on layered transition metal oxide(TMO)-based cathode materials and metal oxide-based anode materials for Li-ion batteries, their precursors generally follow different or even complex synthesis routes. To share one route for preparing precursors of the cathode and anode materials, herein, we demonstrate a facile co-precipitation method to fabricate Ni-rich hydroxide precursors of Ni0.8Co0.1Mn0.1(OH)2. Ni-rich layered oxide of LiNi0.8Co0.1Mn0.1O2 is obtained by lithiation of the precursor in air. An NiO-based anode material is prepared by calcining the precursor or multi-walled carbon nanotubes (MWCNTs) incorporated precursors. The pre-addition of ammonia solution can simplify the co-precipitation procedures and the use of an air atmosphere can also make the heat treatment facile. LiNi0.8Co0.1Mn0.1O2 as the cathode material delivers a reversible capacity of 194 mA h g-1 at 40 mA g-1 and a notable cycling retention of 88.8% after 100 cycles at 200 mA g-1. This noticeable performance of the cathode arises from a decent particle morphology and high crystallinity of the layered oxides. As the anode material, the MWCNTs-incorporated oxides deliver a much higher reversible capacity of 811.1 mA h g-1 after 200 cycles compared to the pristine oxides without MWCNTs. The improvement on electrochemical performance can be attributed to synergistic effects from MWCNTs incorporation, including reinforced electronic conductivity, rich meso-pores and an alleviated volume effect. This facile and sharing method may offer an integrated and economical approach for commercial production of Ni-rich electrode materials for Li-ion batteries.

Quantitative transmission electron microscopy and atom probe tomography study of Ag-dependent precipitation of Ω phase in Al-Cu-Mg alloys

Energy Technology Data Exchange (ETDEWEB)

Bai, Song; Ying, Puyou [Key Laboratory of Nonferrous Metal Materials Science and Engineering, Ministry of Education, Central South University, Changsha 410083 (China); School of Material Science and Engineering, Central South University, Changsha 410083 (China); Liu, Zhiyi, E-mail: liuzhiyi@csu.edu.cn [Key Laboratory of Nonferrous Metal Materials Science and Engineering, Ministry of Education, Central South University, Changsha 410083 (China); School of Material Science and Engineering, Central South University, Changsha 410083 (China); Wang, Jian; Li, Junlin [Key Laboratory of Nonferrous Metal Materials Science and Engineering, Ministry of Education, Central South University, Changsha 410083 (China); School of Material Science and Engineering, Central South University, Changsha 410083 (China)

2017-02-27

The close association between the Ω precipitation and various Ag additions is systematically investigated by quantitative transmission electron microscopy and atom probe tomography analysis. Our results suggest that the precipitation of Ω phase is strongly dependent on Ag variations. Increasing the bulk Ag content favors a denser Ω precipitation and hence leads to a greater age-hardening response of Al-Cu-Mg-Ag alloy. This phenomenon, as proposed by proximity histograms, is directly related to the greater abundance of Ag solutes within Ω precursors. This feature lowers its nucleation barrier and increases the nucleation rate of Ω phase, finally contributes to the enhanced Ω precipitation. Also, it is noted that increasing Ag remarkably restricts the precipitation of θ' phase.

Does objective cluster analysis serve as a useful precursor to seasonal precipitation prediction at local scale? Application to western Ethiopia

Science.gov (United States)

Zhang, Ying; Moges, Semu; Block, Paul

2018-01-01

Prediction of seasonal precipitation can provide actionable information to guide management of various sectoral activities. For instance, it is often translated into hydrological forecasts for better water resources management. However, many studies assume homogeneity in precipitation across an entire study region, which may prove ineffective for operational and local-level decisions, particularly for locations with high spatial variability. This study proposes advancing local-level seasonal precipitation predictions by first conditioning on regional-level predictions, as defined through objective cluster analysis, for western Ethiopia. To our knowledge, this is the first study predicting seasonal precipitation at high resolution in this region, where lives and livelihoods are vulnerable to precipitation variability given the high reliance on rain-fed agriculture and limited water resources infrastructure. The combination of objective cluster analysis, spatially high-resolution prediction of seasonal precipitation, and a modeling structure spanning statistical and dynamical approaches makes clear advances in prediction skill and resolution, as compared with previous studies. The statistical model improves versus the non-clustered case or dynamical models for a number of specific clusters in northwestern Ethiopia, with clusters having regional average correlation and ranked probability skill score (RPSS) values of up to 0.5 and 33 %, respectively. The general skill (after bias correction) of the two best-performing dynamical models over the entire study region is superior to that of the statistical models, although the dynamical models issue predictions at a lower resolution and the raw predictions require bias correction to guarantee comparable skills.

The use of microemulsions for the synthesis of oxalate precursors of YBaCuO superconduction oxide

International Nuclear Information System (INIS)

Wang, L.; Zhang, Y.; Muhammed, M.

1992-01-01

Although emulsion technique has been used as an advanced separation method, little attention has been paid to the particular feature of emulsions as a powerful reaction media for synthesis of powders, e.g., precipitation of fine particles. In the present paper, the authors report the use of some microemulsion systems as a reaction media in a controlled coprecipitation of the oxalate precursors of superconducting YBa 2 Cu 3 O 7-δ ceramics. The phase diagram of the system: oil (hydrocarbon) - surfactant (Aerosol Orange T) - water, in the absence and presence of nitric/oxalic acids and nitrates, have been systematically investigated. Several hydrocarbons, n-hexane, n-haptene and n-octane have been tested. The different stability regions of microemulsions have been determined. The oxalate coprecipitation of Y, Ba and Cu from nitrate solution was studied under various operating conditions, pH, ratio of oil/surfactant/water and ratio of Y/Ba/Cu/.H 2 C 2 O 4 2 . The chemical and morphological properties of the oxalate powders obtained in the microemulsion systems have been examined by different techniques, e.g., ICP, TGA, XRD and SEM. By XRD, the optimum products are found to be amorphous oxalate composite with exact required stoichiometry and high homogeneity. The average size of the dispersed particles is 50-70 nm while the mean diameter of the agglomerates is around 300 nm. The best sinters bulk sample has T, (R = 0) at 92 K. These powders are used as fine precursors for the synthesis of high T c superconducting ceramics as bulk material and particularly thick films

Zinc and nickel removal in limestone based treatment of acid mine drainage: The relative role of adsorption and co-precipitation

International Nuclear Information System (INIS)

Miller, Andrew; Wildeman, Thomas; Figueroa, Linda

2013-01-01

Highlights: • Limestone treatment of mining impacted water was simulated in batch reactors. • Zinc and nickel removals were quantified/characterized with a sequential extraction. • Removals were described with a surface complexation and a surface precipitation model. • Extraction/modeling results imply mechanisms beyond adsorption dominate metal removal. - Abstract: Mining influenced water may contain high metal and sulfate loads, and have low pH (acid mine drainage). Removal of these metals prior to environmental discharge is critical to maintain ecosystem vitality. Limestone based passive treatment systems are commonly used for pH neutralization. The same conditions that lead to pH neutralization may also remove a substantial amount of metals from solution, but the connection between treatment conditions and metal removal are not well understood. In this study, zinc and nickel removals are quantified in batch reactor simulated limestone treatment of acid mine drainage. The resulting solid phase is characterized with a sequential extraction procedure, and the removals are interpreted using surface complexation and surface precipitation models. Zinc and nickel removals are closely linked to the initial iron concentration in the mine water, but are also affected by pH, alkalinity, calcium and sulfate concentrations. The surface complexation model was based on literature descriptions of hydrous ferric oxide. In order to obtain a sufficient fit to the data, the surface site density was increased to an unrealistically high value. Uptake data was also fit to an existing surface precipitation model. The values used are similar to those found in previous studies. Both models indicate that adsorption is not the dominant removal process in the treatment system. Using adsorption only models will generally underpredict metal removals within limestone based treatment systems

Thermal decomposition and spectroscopic investigation of a new aqueous glycolato(-peroxo) Ti(IV) solution-gel precursor

International Nuclear Information System (INIS)

De Dobbelaere, Christopher; Mullens, Jules; Hardy, An; Van Bael, Marlies K.

2011-01-01

Highlights: → A totally water based glycolato-Ti(IV) precursor is presented and characterized. → The precursors' thermal decomposition profile depends on the ligand to metal ratio. → Titanium is coordinated in an unidentate fashion by the glycolate anion. → Smooth and uniform TiO 2 films can be prepared from the precursor solution. - Abstract: A new aqueous solution-gel precursor based on water soluble glycolato(-peroxo)-Ti(IV) complexes is developed for the preparation of TiO 2 films. With regard to the decomposition of complexes towards oxide formation, it is important to gain insight in the chemical transformations inside the precursor during thermal treatment. Therefore, the thermo-oxidative decomposition pathway of a gel obtained by slow evaporation of the precursor solution is described based on hyphenated thermogravimetric analysis with Fourier transform infrared spectroscopy (TGA-FTIR) and mass spectrometry (TGA-MS). Pure glycolic acid is used as a reference system for this study. By varying the molar glycolic acid to Ti(IV) ratio, the thermal decomposition of the gel can be drastically shortened and the profile's course changed. Gel structure and chemical changes in the gel upon heating are also studied by means of off-line FTIR. A unidentate coordination of the titanium(IV) ion by the carboxylate group of the glycolato ligands and the involvement of the hydroxyl group is confirmed. Phase formation at certain points in the thermal decomposition is studied by X-ray diffraction and Raman spectroscopy. Finally, it is proven that the new precursor is a valuable candidate for the deposition of low carbon containing solution-gel films which can ultimately be converted into smooth and uniform TiO 2 films.

Decomposition of oxalate precipitates by photochemical reaction

International Nuclear Information System (INIS)

Yoo, J.H.; Kim, E.H.

1998-01-01

A photo-radiation method was applied to decompose oxalate precipitates so that it can be dissolved into dilute nitric acid. This work has been studied as a part of partitioning of minor actinides. Minor actinides can be recovered from high-level wastes as oxalate precipitates, but they tend to be coprecipitated together with lanthanide oxalates. This requires another partitioning step for mutual separation of actinide and lanthanide groups. In this study, therefore, the photochemical decomposition mechanism of oxalates in the presence of nitric acid was elucidated by experimental work. The decomposition of oxalates was proved to be dominated by the reaction with hydroxyl radical generated from the nitric acid, rather than with nitrite ion also formed from nitrate ion. The decomposition rate of neodymium oxalate, which was chosen as a stand-in compound representing minor actinide and lanthanide oxalates, was found to be 0.003 M/hr at the conditions of 0.5 M HNO 3 and room temperature when a mercury lamp was used as a light source. (author)

Decomposition of oxalate precipitates by photochemical reaction

International Nuclear Information System (INIS)

Jae-Hyung Yoo; Eung-Ho Kim

1999-01-01

A photo-radiation method was applied to decompose oxalate precipitates so that it can be dissolved into dilute nitric acid. This work has been studied as a part of partitioning of minor actinides. Minor actinides can be recovered from high-level wastes as oxalate precipitates, but they tend to be coprecipitated together with lanthanide oxalates. This requires another partitioning step for mutual separation of actinide and lanthanide groups. In this study, therefore, some experimental work of photochemical decomposition of oxalate was carried out to prove its feasibility as a step of partitioning process. The decomposition of oxalic acid in the presence of nitric acid was performed in advance in order to understand the mechanistic behaviour of oxalate destruction, and then the decomposition of neodymium oxalate, which was chosen as a stand-in compound representing minor actinide and lanthanide oxalates, was examined. The decomposition rate of neodymium oxalate was found as 0.003 mole/hr at the conditions of 0.5 M HNO 3 and room temperature when a mercury lamp was used as a light source. (author)

Organic acids as analytical reagent: Part 1. Estimation of zirconium by gallic acid

International Nuclear Information System (INIS)

Pande, C.S.; Singh, A.K.; Kumar, Ashok

1975-01-01

Gallic acid has been found to be a selective reagent for the estimation of zirconium. The acid gives crystalline precipitate at pH of 4.8. The precipitate is ignited and weighed as ZrO 2 . Cations like Ca +2 , Ba +2 , Sr +2 , Mn +2 , Co +2 , Ni +2 , Fe +3 do not interfere in the estimation. (author)

UV and VUV characteristics of (YGd)2O3:Eu phosphor particles prepared by spray pyrolysis from polymeric precursors

International Nuclear Information System (INIS)

Kim, E.J.; Kang, Y.C.; Park, H.D.; Ryu, S.K.

2003-01-01

Red-emitting (YGd) 2 O 3 :Eu phosphor particles, with high luminescence efficiency under vacuum ultraviolet (VUV) and ultraviolet (UV) excitation, were prepared by a large-scale spray pyrolysis process. To control the morphology of phosphor particles under severe preparation conditions, spray solution with polymeric precursors were introduced in spray pyrolysis. The prepared (YGd) 2 O 3 :Eu phosphor particles had spherical shape and filled morphology even after post-treatment irrespective of Gd/Y ratio. In the case of solution with polymeric precursors, long polymeric chains formed by esterification reaction in a hot tubular reactor; the droplets turned into viscous gel, which retarded the precipitation of nitrate salts and promoted the volume precipitation of droplets. The brightness of (YGd) 2 O 3 :Eu phosphor particles increased with increasing gadolinium content, and the Gd 2 O 3 :Eu phosphor had the highest luminescence intensity under UV and VUV excitation. The maximum peak intensity of Gd 2 O 3 :Eu phosphor particles under UV and VUV were 118 and 110% of the commercial Y 2 O 3 :Eu phosphor particles, respectively

Acid Rain. LC Science Tracer Bullet.

Science.gov (United States)

Hollmann, Pauline, Comp.

The term "acid rain," also called "acid precipitation," generally refers to any precipitation having a pH value of less than 5.6. This guide to the literature on acid rain in the collections of the Library of Congress is not necessarily intended to be a comprehensive bibliography. It is designed to provide the reader with a set…

Does objective cluster analysis serve as a useful precursor to seasonal precipitation prediction at local scale? Application to western Ethiopia

Directory of Open Access Journals (Sweden)

Y. Zhang

2018-01-01

Full Text Available Prediction of seasonal precipitation can provide actionable information to guide management of various sectoral activities. For instance, it is often translated into hydrological forecasts for better water resources management. However, many studies assume homogeneity in precipitation across an entire study region, which may prove ineffective for operational and local-level decisions, particularly for locations with high spatial variability. This study proposes advancing local-level seasonal precipitation predictions by first conditioning on regional-level predictions, as defined through objective cluster analysis, for western Ethiopia. To our knowledge, this is the first study predicting seasonal precipitation at high resolution in this region, where lives and livelihoods are vulnerable to precipitation variability given the high reliance on rain-fed agriculture and limited water resources infrastructure. The combination of objective cluster analysis, spatially high-resolution prediction of seasonal precipitation, and a modeling structure spanning statistical and dynamical approaches makes clear advances in prediction skill and resolution, as compared with previous studies. The statistical model improves versus the non-clustered case or dynamical models for a number of specific clusters in northwestern Ethiopia, with clusters having regional average correlation and ranked probability skill score (RPSS values of up to 0.5 and 33 %, respectively. The general skill (after bias correction of the two best-performing dynamical models over the entire study region is superior to that of the statistical models, although the dynamical models issue predictions at a lower resolution and the raw predictions require bias correction to guarantee comparable skills.

Sulfonic-based precursors (SAPs for silica mesostructures: Advances in synthesis and applications

Directory of Open Access Journals (Sweden)

Sadegh Rostamnia*

2016-01-01

Full Text Available Sulfonic acid-based precursors (SAP play an important role in tailoring mesoporous silica’s and convert them to a solid acid catalyst with a Bronsted-type nature. These kinds of solid acids contribute to sustainable and green chemistry by their heterogeneous, recyclable, and high efficiency features. Therefore, knowing the properties and reactivity of SAPs can guide us to manufacture a sulfonated mesostructures compatible with reaction type and conditions. In the present review, some of the important SAPs, their reactivity and mechanism of functionalization are discussed.

Fabrication of Tb3Al5O12 transparent ceramics using co-precipitated nanopowders

Science.gov (United States)

Dai, Jiawei; Pan, Yubai; Wang, Wei; Luo, Wei; Xie, Tengfei; Kou, Huamin; Li, Jiang

2017-11-01

Terbium aluminum garnet (TAG) precursor was synthesized by a co-precipitation method from a mixed solution of terbium and aluminum nitrates using ammonium hydrogen carbonate (AHC) as the precipitant. The powders calcined at different temperatures were investigated by XRD, FTIR and FESEM in order to choose the optimal calcination temperature. Fine and low-agglomerated TAG powders with average particle size of 88 nm were obtained by calcining the precursor at 1100 °C for 4 h. Using this powder as starting material, TAG transparent ceramics were fabricated by vacuum sintering combined with hot isostatic pressing (HIP) sintering. For the sample pre-sintered at 1700 °C for 20 h with HIP post-treated at 1700 °C for 3 h, the average grain size is about 3.9 μm and the in-line transmittance is beyond 55% in the region of 500-1600 nm, reaching a maximum transmittance of 64.2% at the wavelength of 1450 nm. The Verdet constant at 633 nm is measured to be -178.9 rad T-1 m-1, which is 33% larger than that of the commercial TGG single crystal (-134 rad T-1 m-1).

Recovery Ce from Ce - TBP Used Oxalic Acid

International Nuclear Information System (INIS)

Purwani, MV; Subagiono, R.; Suyanti

2007-01-01

Recovery or stripping Ce from Ce - TBP product of monazite sand used oxalic acid. Ce - TBP as organic phase and oxalic acid as aqueous phase and as strong precipitant compound to precipitate metal element. The stripping product as Ce - oxalic precipitate. The influence parameter were percentage of oxalic acid, volume ratio of Ce-TBP with oxalic acid, time and rate of stripping. At stripping of 25 ml Ce - TBP used oxalic acid, the optimum condition were achieve at using 5% oxalic acid, volume ratio of Ce - TBP : 5% oxalic acid = 1 : 1, time of stripping 7.5 minute and rate of stripping 150 rpm. At the optimum condition was obtained the recovery efficiency was 100%. (author)

Binding interactions between yeast tRNA ligase and a precursor transfer ribonucleic acid containing two photoreactive uridine analogues

International Nuclear Information System (INIS)

Tanner, N.K.; Hanna, M.M.; Abelson, J.

1988-01-01

Yeast tRNA ligase, from Saccharomyces cerevisiae, is one of the protein components that is involved in the splicing reaction of intron-containing yeast precursor tRNAs. It is an unusual protein because it has three distinct catalytic activities. It functions as a polynucleotide kinase, as a cyclic phosphodiesterase, and as an RNA ligase. We have studied the binding interactions between ligase and precursor tRNAs containing two photoreactive uridine analogues, 4-thiouridine and 5-bromouridine. When irradiated with long ultraviolet light, RNA containing these analogues can form specific covalent bonds with associated proteins. In this paper, we show that 4-thiouridine triphosphate and 5-bromouridine triphosphate were readily incorporated into a precursor tRNA(Phe) that was synthesized, in vitro, with bacteriophage T7 RNA polymerase. The analogue-containing precursor tRNAs were authentic substrates for the two splicing enzymes that were tested (endonuclease and ligase), and they formed specific covalent bonds with ligase when they were irradiated with long-wavelength ultraviolet light. We have determined the position of three major cross-links and one minor cross-link on precursor tRNA(Phe) that were located within the intron and near the 3' splice site. On the basis of these data, we present a model for the in vivo splicing reaction of yeast precursor tRNAs

Whole-cell fungal transformation of precursors into dyes

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Jarosz-Wilkołazka Anna

2010-07-01

Full Text Available Abstract Background Chemical methods of producing dyes involve extreme temperatures and unsafe toxic compounds. Application of oxidizing enzymes obtained from fungal species, for example laccase, is an alternative to chemical synthesis of dyes. Laccase can be replaced by fungal biomass acting as a whole-cell biocatalyst with properties comparable to the isolated form of the enzyme. The application of the whole-cell system simplifies the transformation process and reduces the time required for its completion. In the present work, four fungal strains with a well-known ability to produce laccase were tested for oxidation of 17 phenolic and non-phenolic precursors into stable and non-toxic dyes. Results An agar-plate screening test of the organic precursors was carried out using four fungal strains: Trametes versicolor, Fomes fomentarius, Abortiporus biennis, and Cerrena unicolor. Out of 17 precursors, nine were transformed into coloured substances in the presence of actively growing fungal mycelium. The immobilized fungal biomass catalyzed the transformation of 1 mM benzene and naphthalene derivatives in liquid cultures yielding stable and non-toxic products with good dyeing properties. The type of fungal strain had a large influence on the absorbance of the coloured products obtained after 48-hour transformation of the selected precursors, and the most effective was Fomes fomentarius (FF25. Whole-cell transformation of AHBS (3-amino-4-hydroxybenzenesulfonic acid into a phenoxazinone dye was carried out in four different systems: in aqueous media comprising low amounts of carbon and nitrogen source, in buffer, and in distilled water. Conclusions This study demonstrated the ability of four fungal strains belonging to the ecological type of white rot fungi to transform precursors into dyes. This paper highlights the potential of fungal biomass for replacing isolated enzymes as a cheaper industrial-grade biocatalyst for the synthesis of dyes and other

Oral bioavailability of the ether lipid plasmalogen precursor, PPI-1011, in the rabbit: a new therapeutic strategy for Alzheimer's disease

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Wood Paul L

2011-12-01

Full Text Available Abstract Introduction Docosahexaenoic acid (DHA and DHA-containing ethanolamine plasmalogens (PlsEtn are decreased in the brain, liver and the circulation in Alzheimer's disease. Decreased supply of plasmalogen precursors to the brain by the liver, as a result of peroxisomal deficits is a process that probably starts early in the AD disease process. To overcome this metabolic compromise, we have designed an orally bioavailable DHA-containing ether lipid precursor of plasmalogens. PPI-1011 is an alkyl-diacyl plasmalogen precursor with palmitic acid at sn-1, DHA at sn-2 and lipoic acid at sn-3. This study outlines the oral pharmacokinetics of this precursor and its conversion to PlsEtn and phosphatidylethanolamines (PtdEtn. Methods Rabbits were dosed orally with PPI-1011 in hard gelatin capsules for time-course and dose response studies. Incorporation into PlsEtn and PtdEtn was monitored by LC-MS/MS. Metabolism of released lipoic acid was monitored by GC-MS. To monitor the metabolic fate of different components of PPI-1011, we labeled the sn-1 palmitic acid, sn-2 DHA and glycerol backbone with13C and monitored their metabolic fates by LC-MS/MS. Results PPI-1011 was not detected in plasma suggesting rapid release of sn-3 lipoic acid via gut lipases. This conclusion was supported by peak levels of lipoic acid metabolites in the plasma 3 hours after dosing. While PPI-1011 did not gain access to the plasma, it increased circulating levels of DHA-containing PlsEtn and PtdEtn. Labeling experiments demonstrated that the PtdEtn increases resulted from increased availability of DHA released via remodeling at sn-2 of phospholipids derived from PPI-1011. This release of DHA peaked at 6 hrs while increases in phospholipids peaked at 12 hr. Increases in circulating PlsEtn were more complex. Labeling experiments demonstrated that increases in the target PlsEtn, 16:0/22:6, consisted of 2 pools. In one pool, the intact precursor received a sn-3

Correlation between precipitation and geographical location of the δ2H values of the fatty acids in milk and bulk milk powder

Science.gov (United States)

Ehtesham, E.; Baisden, W. T.; Keller, E. D.; Hayman, A. R.; Van Hale, R.; Frew, R. D.

2013-06-01

Hydrogen isotope ratios (δ2H) have become a tool for food traceability and authentication of agricultural products. The principle is that the isotopic composition of the produce is influenced by environmental and biological factors and hence exhibits a spatial differentiation of δ2H. This study investigates the variation in δ2H values of New Zealand milk, both in the bulk powder and individual fatty acids extracted from milk samples from dairy factories across New Zealand. Multivariate statistical analyses were used to test for relationships between δ2H of bulk milk powder, milk fatty acid and geographical location. Milk powder samples from different regions of New Zealand were found to exhibit patterns in isotopic composition similar to the corresponding regional precipitation associated with their origin. A model of δ2H in precipitation was developed based on measurements between 2007 and 2010 at 51 stations across New Zealand (Frew and Van Hale, 2011). The model uses multiple linear regressions to predict daily δ2H from 2 geographic and 5 rain-weighted climate variables from the 5 × 5 km New Zealand Virtual Climate Station Network (VCSN). To approximate collection radius for a drying facility the modelled values were aggregated within a 50 km radius of each dairy factory and compared to observed δ2H values of precipitation and bulk milk powder. Daily δ2H predictions for the period from August to December for the area surrounding the sample collection sites were highly correlated with the δ2H values of bulk milk powder. Therefore the δ2H value of milk fatty acids demonstrates promise as a tool for determining the provenance of milk powders and products where milk powder is an ingredient. Separation of milk powder origin to geographic sub-regions within New Zealand was achieved. Hydrogen isotope measurements could be used to complement traditional tracking systems in verifying point of origin.

Synthesis and characterization of Co3O4 prepared from atmospheric pressure acid leach liquors of nickel laterite ores

Science.gov (United States)

Meng, Long; Guo, Zhan-cheng; Qu, Jing-kui; Qi, Tao; Guo, Qiang; Hou, Gui-hua; Dong, Peng-yu; Xi, Xin-guo

2018-01-01

A chemical precipitation-thermal decomposition method was developed to synthesize Co3O4 nanoparticles using cobalt liquor obtained from the atmospheric pressure acid leaching process of nickel laterite ores. The effects of the precursor reaction temperature, the concentration of Co2+, and the calcination temperature on the specific surface area, morphology, and the electrochemical behavior of the obtained Co3O4 particles were investigated. The precursor basic cobaltous carbonate and cobaltosic oxide products were characterized and analyzed by Fourier transform infrared spectroscopy, thermogravimetric differential thermal analysis, X-ray diffraction, field-emission scanning electron microscopy, specific surface area analysis, and electrochemical analysis. The results indicate that the specific surface area of the Co3O4 particles with a diameter of 30 nm, which were obtained under the optimum conditions of a precursor reaction temperature of 30°C, 0.25 mol/L Co2+, and a calcination temperature of 350°C, was 48.89 m2/g. Electrodes fabricated using Co3O4 nanoparticles exhibited good electrochemical properties, with a specific capacitance of 216.3 F/g at a scan rate of 100 mV/s.

Technical Note: Methionine, a precursor of methane in living plants

Science.gov (United States)

Lenhart, K.; Althoff, F.; Greule, M.; Keppler, F.

2015-03-01

When terrestrial plants were identified as producers of the greenhouse gas methane, much discussion and debate ensued not only about their contribution to the global methane budget but also with regard to the validity of the observation itself. Although the phenomenon has now become more accepted for both living and dead plants, the mechanism of methane formation in living plants remains to be elucidated and its precursor compounds to be identified. We made use of stable isotope techniques to verify the in vivo formation of methane, and, in order to identify the carbon precursor, 13C positionally labeled organic compounds were employed. Here we show that the amino acid L-methionine acts as a methane precursor in living plants. Employing 13C-labeled methionine clearly identified the sulfur-bound methyl group of methionine as a carbon precursor of methane released from lavender (Lavandula angustifolia). Furthermore, when lavender plants were stressed physically, methane release rates and the stable carbon isotope values of the emitted methane greatly increased. Our results provide additional support that plants possess a mechanism for methane production and suggest that methionine might play an important role in the formation of methane in living plants, particularly under stress conditions.

Geological and hydrochemical sensitivity of the eastern United States to acid precipitation

Energy Technology Data Exchange (ETDEWEB)

Hendrey, G.R.; Galloway, J.N.; Norton, S.A.; Schofield, C.L.; Shaffer, P.W.; Burns, D.A.

1980-03-01

A new analysis of bedrock geology maps of the eastern US constitutes a simple model for predicting areas which might be impacted by acid precipitation and it allows much greater resolution for detecting sensitivity than has previously been available for the region. Map accuracy has been verified by examining current alkalinities and pH's of waters in several test states, including Maine, New Hampshire, New York, Virginia and North Carolina. In regions predicted to be highly sensitive, alkalinities in upstream sites were generally low. Many areas of the eastern US are pinpointed in which some of the surface waters, especially upstream reaches, may be sensitive to acidification. Pre-1970 data were compared to post-1975 data, revealing marked declines in both alkalinity and pH of sensitive waters of two states tested, North Carolina, where pH and alkalinity have decreased in 80% of 38 streams and New Hampshire, where pH in 90% of 49 streams and lakes has decreased since 1949. These sites are predicted to be sensitive by the geological map on the basis of their earlier alkalinity values. The map is to be improved by the addition of a soils component.

Studies on the distribution of radioactivity in the organism and rate of incorporation of radioactivity into the tissue proteins of monogastric animals after intravenous injection of tracer amino acids

International Nuclear Information System (INIS)

Simon, O.; Muenchmeyer, R.; Bergner, H.; Zebrowska, T.

1976-01-01

Radioactive amino acids ( 14 C leucine and 3 H lysine) were administrated to pigs by means of a catheter tube into the jugular vein. Subsequently, the time pattern of the distribution of the specific amino acid radioactivity was followed in the TCE soluble and TCE precipitable fractions of the blood plasma (TCE = trichloroacetic acid). Rats were injected 14 C into the portal vein. The animals were killed after incorporation periods of 2 to 60 minutes, and the levels of specific radioactivity were estimated in the TCE soluble and TCE precipitable fractions of the blood plasma, in the liver and in the skeletal muscles. The experimental results indicated that the specific radioactivity of the tracer amino acids and the rate of incorporation of radioactivity into tissue proteins were influenced by the size of the free amino acid pool within the range of distribution of the tracer. An estimation of the magnitude of the pool of free amino acids within the distribution range of the tracer can be obtained from the curve pattern for the decline of specific radioactivity of the corresponding free amino acid in the blood plasma. This pool exhibits a high rate of turnover. In all studies made to evaluate in vivo processes of protein synthesis using radioactive tracer amino acids it will be particularly important that consideration is given to the specific radioactivity of the amino acid in the precursor pool for protein synthesis. (author)

Synthesis, properties and space applications of chemically precipitated YBa/sub 2/Cu/sub 3/O/sub 7-x/ superconducting powders

International Nuclear Information System (INIS)

Trivedi, A.; Sundahl, R.C.; Olson, W.L.; Welsh, L.B.; Polak, A.J.; Dolgin, B.P.; Barder, T.J.; Karasek, K.R.; Parker, C.A.

1988-01-01

Processing properties of and chemically precipitated YBa/sub 2/Cu/sub 3/O/sub 7-x/ powders were evaluated. The authors have successfully developed a method for precipitating stoichiometric oxalate precursors for YBa/sub 2/Cu/sub 3/O/sub 7-x/ powders. Precipitation and calcination conditions were found to dramatically impact upon key powder characteristics such as particle size, morphology, phase composition and microscopic homogeneity. Four space applications were identified: a superconducting motor/generator, a magnetic bearing, an electromagnetic coupling, and a motor commutator. The primary device, a motor, would make use of superconducting windings and a superconducting flux bottle to improve efficiency

Thermal decomposition and spectroscopic investigation of a new aqueous glycolato(-peroxo) Ti(IV) solution-gel precursor

Energy Technology Data Exchange (ETDEWEB)

De Dobbelaere, Christopher, E-mail: christopher.dedobbelaere@uhasselt.be [Hasselt University, Institute for Materials Research, Inorganic and Physical Chemistry, Agoralaan Building D, B-3590 Diepenbeek (Belgium); Mullens, Jules, E-mail: jules.mullens@uhasselt.be [Hasselt University, Institute for Materials Research, Inorganic and Physical Chemistry, Agoralaan Building D, B-3590 Diepenbeek (Belgium); Hardy, An, E-mail: an.hardy@uhasselt.be [Hasselt University, Institute for Materials Research, Inorganic and Physical Chemistry, Agoralaan Building D, B-3590 Diepenbeek (Belgium); IMEC vzw, Division IMOMEC, Agoralaan Building D, B-3590 Diepenbeek (Belgium); Van Bael, Marlies K., E-mail: marlies.vanbael@uhasselt.be [Hasselt University, Institute for Materials Research, Inorganic and Physical Chemistry, Agoralaan Building D, B-3590 Diepenbeek (Belgium); IMEC vzw, Division IMOMEC, Agoralaan Building D, B-3590 Diepenbeek (Belgium)

2011-06-10

Highlights: {yields} A totally water based glycolato-Ti(IV) precursor is presented and characterized. {yields} The precursors' thermal decomposition profile depends on the ligand to metal ratio. {yields} Titanium is coordinated in an unidentate fashion by the glycolate anion. {yields} Smooth and uniform TiO{sub 2} films can be prepared from the precursor solution. - Abstract: A new aqueous solution-gel precursor based on water soluble glycolato(-peroxo)-Ti(IV) complexes is developed for the preparation of TiO{sub 2} films. With regard to the decomposition of complexes towards oxide formation, it is important to gain insight in the chemical transformations inside the precursor during thermal treatment. Therefore, the thermo-oxidative decomposition pathway of a gel obtained by slow evaporation of the precursor solution is described based on hyphenated thermogravimetric analysis with Fourier transform infrared spectroscopy (TGA-FTIR) and mass spectrometry (TGA-MS). Pure glycolic acid is used as a reference system for this study. By varying the molar glycolic acid to Ti(IV) ratio, the thermal decomposition of the gel can be drastically shortened and the profile's course changed. Gel structure and chemical changes in the gel upon heating are also studied by means of off-line FTIR. A unidentate coordination of the titanium(IV) ion by the carboxylate group of the glycolato ligands and the involvement of the hydroxyl group is confirmed. Phase formation at certain points in the thermal decomposition is studied by X-ray diffraction and Raman spectroscopy. Finally, it is proven that the new precursor is a valuable candidate for the deposition of low carbon containing solution-gel films which can ultimately be converted into smooth and uniform TiO{sub 2} films.

Fabrication of calcite blocks from gypsum blocks by compositional transformation based on dissolution-precipitation reactions in sodium carbonate solution.

Science.gov (United States)

Ishikawa, Kunio; Kawachi, Giichiro; Tsuru, Kanji; Yoshimoto, Ayami

2017-03-01

Calcium carbonate (CaCO 3 ) has been used as a bone substitute, and is a precursor for carbonate apatite, which is also a promising bone substitute. However, limited studies have been reported on the fabrication of artificial calcite blocks. In the present study, cylindrical calcite blocks (ϕ6×3mm) were fabricated by compositional transformation based on dissolution-precipitation reactions using different calcium sulfate blocks as a precursor. In the dissolution-precipitation reactions, both CaSO 4 ·2H 2 O and CaSO 4 transformed into calcite, a polymorph of CaCO 3 , while maintaining their macroscopic structure when immersed in 1mol/L Na 2 CO 3 solution at 80°C for 1week. The diametral tensile strengths of the calcite blocks formed using CaSO 4 ·2H 2 O and CaSO 4 were 1.0±0.3 and 2.3±0.7MPa, respectively. The fabrication of calcite blocks using CaSO 4 ·2H 2 O and CaSO 4 proposed in this investigation may be a useful method to produce calcite blocks because of the self-setting ability and high temperature stability of gypsum precursors. Copyright © 2016 Elsevier B.V. All rights reserved.

Selective Precipitation of Thorium lodate from a Tartaric Acid-Hydrogen Peroxide Medium Application to Rapid Spectrophotometric Determination of Thorium in Silicate Rocks and in Ores

Science.gov (United States)

Grimaldi, F.S.

1957-01-01

This paper presents a selective iodate separation of thorium from nitric acid medium containing d-tartaric acid and hydrogen peroxide. The catalytic decomposition of hydrogen peroxide is prevented by the use of 8quinolinol. A few micrograms of thorium are separated sufficiently clean from 30 mg. of such oxides as cerium, zirconium, titanium, niobium, tantalum, scandium, or iron with one iodate precipitation to allow an accurate determination of thorium with the thoronmesotartaric acid spectrophotometric method. The method is successful for the determination of 0.001% or more of thorium dioxide in silicate rocks and for 0.01% or more in black sand, monazite, thorite, thorianite, eschynite, euxenite, and zircon.

Endogenous peptide profile for elucidating biosynthetic processing of the ghrelin precursor.

Science.gov (United States)

Tsuchiya, Takashi; Iwakura, Hiroshi; Minamino, Naoto; Kangawa, Kenji; Sasaki, Kazuki

2017-09-02

Ghrelin is an orexigenic peptide primarily produced by gastric endocrine cells. The biosynthetic cleavage site of ghrelin has been well documented, but how its downstream region undergoes proteolytic processing remains poorly explored. Here, we provide the first snapshot of endogenous peptides from the ghrelin precursor by profiling the secretopeptidome of cultured mouse ghrelin-producing cells during exocytosis. Mapping of MS/MS sequenced peptides to the precursor highlighted three atypical monobasic processing sites, including the established C-terminus of ghrelin and the N-terminal cleavage site for obestatin, a putative 23-amino-acid C-terminally amidated peptide. However, we found that mouse obestatin does not occur in the form originally reported, but that a different amidation site is used to generate a shorter peptide. These data can be extended to study and characterize the precursor-derived peptides located downstream of ghrelin in different biological contexts. Copyright © 2017 Elsevier Inc. All rights reserved.

Structural characterization of FeVO{sub 4} synthesized by co-precipitation method

Energy Technology Data Exchange (ETDEWEB)

Bera, Ganesh; Sinha, Sourav; Rambabu, P.; Das, P.; Gupta, A. K.; Turpu, G. R., E-mail: dr.tgreddy@gmail.com [Department of Pure and Applied Physics, Guru Ghasidas Vishwavidyalaya, Koni, Bilaspur 495 009 (India)

2016-05-06

A Low temperature method for synthesizing triclinic FeVO{sub 4} nanoparticles is manifested through co-precipitation method. Three precursor materials taken for the synthesis are Iron Nitrate, Ammonium Metavanadate and NaOH along with DI water. The attained precipitate was dried at 100°C for overnight and calcined at different temperatures ranging from 400°C - 650°C. The achieved powdered materials are studied through X-ray diffraction and found to be in pure single phase of P-1 space group symmetry. The crystallite size measured through Scherrer’s method is in found to be in the range of 40-60 nm. Raman spectroscopic studies were carried out at room temperature. Raman spectra is in agreement with the reported structural data of FeVO{sub 4}.

Investigation of gallium redistribution processes during Cu(In,Ga)Se{sub 2} absorber formation from electrodeposited/annealed oxide precursor films

Energy Technology Data Exchange (ETDEWEB)

Sidali, T., E-mail: tarik.sidali@edf.fr; Duchatelet, A.; Chassaing, E.; Lincot, D.

2015-05-01

A way to prepare metallic precursors for CuIn{sub 1−x},Ga{sub x}Se{sub 2} (CIGS) solar cells has been recently introduced leading to efficiencies above 12.4%. It consists in the electrodeposition of Cu-In-Ga mixed oxides in an acidic nitrate aqueous solution followed by thermal reduction and selenization. This paper investigates, in a first part, the nucleation and growth mechanisms taking place during the co-electrodeposition of Cu-In-Ga oxide/hydroxide film. Scanning Electron Microscope observations coupled to Energy Dispersive X-ray spectrometry point out that the deposition is initiated by the formation of metallic copper nuclei. These nuclei enable the growth of Cu-In-Ga oxide film. This observation confirms that freshly deposited copper catalyzes nitrate reduction leading to an increase in the surface pH enabling the precipitation of the Cu-In-Ga hydroxides. In a second part, precursor films were elaborated with increasing Ga(NO{sub 3}){sub 3} concentration. After reduction of the films in hydrogen and selenization heat treatments, X-ray diffraction analysis shows the incorporation of Ga into the CIGS phase with increasing Ga content in the optimal composition range for photovoltaic applications (x = 0.25-0.34). Gallium composition profiles are evidenced in the films with a tendency to higher concentration near the Mo surface. Increasing annealing temperature allows a better homogenization of Ga in the film. The consequences are correlated to optoelectronic measurements (Eg and cell efficiency) with bandgap measurement and cell efficiencies (10 to 12%). - Highlights: • Electrodeposition starts with copper nucleation. • Gallium content in the precursor is tuned by Ga(III) concentration. • Increasing selenization temperature promotes Ga homogenization in CIGS.

Novel method for concentrating and drying polymeric nanoparticles: hydrogen bonding coacervate precipitation.

Science.gov (United States)

D'Addio, Suzanne M; Kafka, Concepcion; Akbulut, Mustafa; Beattie, Patrick; Saad, Walid; Herrera, Margarita; Kennedy, Michael T; Prud'homme, Robert K

2010-04-05

Nanoparticles have significant potential in therapeutic applications to improve the bioavailability and efficacy of active drug compounds. However, the retention of nanometer sizes during concentrating or drying steps presents a significant problem. We report on a new concentrating and drying process for poly(ethylene glycol) (PEG) stabilized nanoparticles, which relies upon the unique pH sensitive hydrogen bonding interaction between PEG and polyacid species. In the hydrogen bonding coacervate precipitation (HBCP) process, PEG protected nanoparticles rapidly aggregate into an easily filterable precipitate upon the addition various polyacids. When the resulting solid is neutralized, the ionization of the acid groups eliminates the hydrogen bonded structure and the approximately 100 nm particles redisperse back to within 10% of their original size when poly(acrylic acid) and citric acid are used and 45% when poly(aspartic acid) is used. While polyacid concentrations of 1-5 wt % were used to form the precipitates, the incorporation of the acid into the PEG layer is approximately 1:1 (acid residue):(ethylene oxide unit) in the final dried precipitate. The redispersion of dried beta-carotene nanoparticles protected with PEG-b-poly(lactide-co-glycolide) polymers dried by HBCP was compared with the redispersion of particles dried by freeze-drying with sucrose as a cryprotectant, spray freeze-drying, and normal drying. Freeze-drying with 0, 2, and 12 wt % sucrose solutions resulted in size increases of 350%, 50%, and 6%, respectively. Spray freeze-drying resulted in particles with increased sizes of 50%, but no cryoprotectant and only moderate redispersion energy was required. Conventional drying resulted in solids that could not be redispersed back to nanometer size. The new HBCP process offers a promising and efficient way to concentrate or convert nanoparticle dispersions into a stable dry powder form.

Relationships between precipitation and surface water chemistry in three Carolina bays

International Nuclear Information System (INIS)

Monegue, R.L.; Jagoe, C.H.

1995-01-01

Carolina Bays are shallow freshwater wetlands, the only naturally occurring lentic systems on the southeastern coastal plain. Bays are breeding sites for many amphibian species, but data on precipitation/surface water relationships and long-term chemical trends are lacking. Such data are essential to interpret major fluctuations in amphibian populations. Surface water and bulk precipitation were sampled bi-weekly for over two years at three bays along a 25 km transect on the Savannah River Site in South Carolina. Precipitation chemistry was similar at all sites; average pH was 4.56, and the major ions were H + (30.8 % of total), and SO 4 (50.3% of total). H + was positively correlated with SO 4 , suggesting the importance of anthropogenic acids to precipitation chemistry. All three bays, Rainbow Bay (RB), Thunder Bay (TB), and Ellenton Bay (EB), contained soft (specific conductivity 5--90 microS/cm), acidic water (pH 4.0--5.9) with DOM from 4--40 mg/L. The major cation for RB, TB, and EB, respectively, was: Mg (30.8 % of total); Na (27% of total); and Ca (34.2% of total). DOM was the major anion for all bays, and SO 4 represented 13 to 28 % of total anions. H + was not correlated to DOM or SO, in RB; H + was positively correlated to DOM and SO 4 in TB, and negatively correlated to DOM and SO 4 in EB. Different biogeochemical processes probably control pH and other chemical variables in each bay. While surface water H + was not directly correlated with precipitation H + , NO 3 , or SO 4 , precipitation and shallow groundwater are dominant water sources for these bays. Atmospheric inputs of anthropogenic acids and other chemicals are important factors influencing bay chemistry

Nrt1 and Tna1-independent export of NAD+ precursor vitamins promotes NAD+ homeostasis and allows engineering of vitamin production.

Directory of Open Access Journals (Sweden)

Peter Belenky

2011-05-01

Full Text Available NAD(+ is both a co-enzyme for hydride transfer enzymes and a substrate of sirtuins and other NAD(+ consuming enzymes. NAD(+ biosynthesis is required for two different regimens that extend lifespan in yeast. NAD(+ is synthesized from tryptophan and the three vitamin precursors of NAD(+: nicotinic acid, nicotinamide and nicotinamide riboside. Supplementation of yeast cells with NAD(+ precursors increases intracellular NAD(+ levels and extends replicative lifespan. Here we show that both nicotinamide riboside and nicotinic acid are not only vitamins but are also exported metabolites. We found that the deletion of the nicotinamide riboside transporter, Nrt1, leads to increased export of nicotinamide riboside. This discovery was exploited to engineer a strain to produce high levels of extracellular nicotinamide riboside, which was recovered in purified form. We further demonstrate that extracellular nicotinamide is readily converted to extracellular nicotinic acid in a manner that requires intracellular nicotinamidase activity. Like nicotinamide riboside, export of nicotinic acid is elevated by the deletion of the nicotinic acid transporter, Tna1. The data indicate that NAD(+ metabolism has a critical extracellular element in the yeast system and suggest that cells regulate intracellular NAD(+ metabolism by balancing import and export of NAD(+ precursor vitamins.

Thermal behaviour of natural and synthetic iron precipitates from mine drainage

Czech Academy of Sciences Publication Activity Database

Pulišová, Petra; Máša, B.; Michalková, E.; Večerníková, Eva; Maříková, Monika; Bezdička, Petr; Murafa, Nataliya; Šubrt, Jan

2014-01-01

Roč. 116, č. 2 (2014), s. 625-632 ISSN 1388-6150 R&D Projects: GA MŠk 7AMB12SK155 Institutional support: RVO:61388980 Keywords : Thermogravimetry * Differential thermal analysis * X-ray diffraction analysis * Acid mine drainage * Iron precipitates * Precipitation with urea Subject RIV: CA - Inorganic Chemistry Impact factor: 2.042, year: 2014

Understanding Acid Rain

Science.gov (United States)

Damonte, Kathleen

2004-01-01

The term acid rain describes rain, snow, or fog that is more acidic than normal precipitation. To understand what acid rain is, it is first necessary to know what an acid is. Acids can be defined as substances that produce hydrogen ions (H+), when dissolved in water. Scientists indicate how acidic a substance is by a set of numbers called the pH…

Characterization of Uranium Solids Precipitated with Aluminosilicates

International Nuclear Information System (INIS)

DUFF, MC

2004-01-01

At the Savannah River Site (SRS), the High-Level Waste (HLW) Tank Farms store and process high-level liquid radioactive wastes from the Canyons and recycle water from the Defense Waste Processing Facility. The waste is concentrated using evaporators to minimize the volume of space required for HLW storage. Recently, the 2H Evaporator was shutdown due to the crystallization of sodium aluminosilicate (NAS) solids (such as cancrinite and sodalite) that contained close to 10 weight percent of elementally-enriched uranium (U). Prior to extensive cleaning,the evaporator deposits resided on the evaporator walls and other exposed internal surfaces within the evaporator pot. Our goal is to support the basis for the continued safe operation of SRS evaporators and to gain more information that could be used to help mitigate U accumulation during evaporator operation. To learn more about the interaction between U(VI) and NAS in HLW salt solutions, we performed several fundamental studies to examine the mechanisms of U accumulation with NAS in highly caustic solutions. This larger group of studies focused on the following processes: co-precipitation/structural incorporation, sorption, and precipitation (with or without NAS), which will be reviewed in this presentation. We will present and discuss local atomic structural characterization data about U that has been co-precipitated with NAS solids (such as amorphous zeolite precursor material and sodalite) using X-ray absorption fine-structure (XAFS) spectroscopic techniques

Synthesis of Barium Titanate from Titanyl Acylate Precursor by Sol-precipitate Method

International Nuclear Information System (INIS)

Thandar Win; Kyaw Naing; Khin Mar Tun

2008-03-01

Nanometersize barium titanates (BaTiO3:BT) powders can be obtained by sol-precipitate method in the presence of polyoxyethylene (20) sorbiton monooleate (Tween-80) as a polymeric surface modifier in a strong alkaline solution (pH > 13). FT-IR, TG/DTA, SEM and XRD were used to investigate the effects of the surfactant influence on the morphology of the obtained BaTiO3 powders. With adding surfactant, a slower rate of hydrolyzation is observed and the rate of condensation is slower. The addition of Tween-80 surfactant in general leads to the formation of smaller particle size of BaTi)3 (70-100 nm). Without adding surfactant, larger particle size of BaTiO3 (100-200 nm) was obtained. The nanometersize BaTiO3 powders were readily sintered at 1000-1200C. Raman-active modes of tetragonal phase BT were detected from Raman spectra of BaTiO3 between 800 0 C to 1200 0 C.

Recovery of yttrium from fluorescent powder of cathode ray tube, CRT: Zn removal by sulphide precipitation

International Nuclear Information System (INIS)

Innocenzi, Valentina; De Michelis, Ida; Ferella, Francesco; Beolchini, Francesca; Kopacek, Bernd; Vegliò, Francesco

2013-01-01

Highlights: • Treatment of fluorescent powder of CRT waste. • Factorial experimental designs to study acid leaching of fluorescent powder and the purification of leach liquors. • Recover of yttrium by precipitation using oxalic acid. • Suitable flowsheet to recover yttrium from fluorescent powder. - Abstract: This work is focused on the recovery of yttrium and zinc from fluorescent powder of cathode ray tube (CRT). Metals are extracted by sulphuric acid in the presence of hydrogen peroxide. Leaching tests are carried out according to a 2 2 full factorial plan and the highest extraction yields for yttrium and zinc equal to 100% are observed under the following conditions: 3 M of sulphuric acid, 10% v/v of H 2 O 2 concentrated solution at 30% v/v, 10% w/w pulp density, 70 °C and 3 h of reaction. Two series of precipitation tests for zinc are carried out: a 2 2 full factorial design and a completely randomized factorial design. In these series the factors investigated are pH of solution during the precipitation and the amount of sodium sulphide added to precipitate zinc sulphide. The data of these tests are used to describe two empirical mathematical models for zinc and yttrium precipitation yields by regression analysis. The highest precipitation yields for zinc are obtained under the following conditions: pH equal to 2–2.5% and 10–12% v/v of Na 2 S concentrated solution at 10% w/v. In these conditions the coprecipitation of yttrium is of 15–20%. Finally further yttrium precipitation experiments by oxalic acid on the residual solutions, after removing of zinc, show that yttrium could be recovered and calcined to obtain the final product as yttrium oxide. The achieved results allow to propose a CRT recycling process based on leaching of fluorescent powder from cathode ray tube and recovery of yttrium oxide after removing of zinc by precipitation. The final recovery of yttrium is 75–80%

Recovery of yttrium from fluorescent powder of cathode ray tube, CRT: Zn removal by sulphide precipitation

Energy Technology Data Exchange (ETDEWEB)

Innocenzi, Valentina, E-mail: valentina.innocenzi1@univaq.it [Department of Industrial Engineering and Information and Economy, University of L’Aquila, Via Giovanni Gronchi n.18, Nucleo Ind.le di Pile, 67100 L’Aquila (Italy); De Michelis, Ida; Ferella, Francesco [Department of Industrial Engineering and Information and Economy, University of L’Aquila, Via Giovanni Gronchi n.18, Nucleo Ind.le di Pile, 67100 L’Aquila (Italy); Beolchini, Francesca [Department of Marine Sciences, Polytechnic Institute of Marche, Via Brecce Bianche, 60131 Ancona (Italy); Kopacek, Bernd [SAT, Austrian Society for Systems Engineering and Automation, Gurkasse 43/2, A-1140 Vienna (Austria); Vegliò, Francesco [Department of Industrial Engineering and Information and Economy, University of L’Aquila, Via Giovanni Gronchi n.18, Nucleo Ind.le di Pile, 67100 L’Aquila (Italy)

2013-11-15

Highlights: • Treatment of fluorescent powder of CRT waste. • Factorial experimental designs to study acid leaching of fluorescent powder and the purification of leach liquors. • Recover of yttrium by precipitation using oxalic acid. • Suitable flowsheet to recover yttrium from fluorescent powder. - Abstract: This work is focused on the recovery of yttrium and zinc from fluorescent powder of cathode ray tube (CRT). Metals are extracted by sulphuric acid in the presence of hydrogen peroxide. Leaching tests are carried out according to a 2{sup 2} full factorial plan and the highest extraction yields for yttrium and zinc equal to 100% are observed under the following conditions: 3 M of sulphuric acid, 10% v/v of H{sub 2}O{sub 2} concentrated solution at 30% v/v, 10% w/w pulp density, 70 °C and 3 h of reaction. Two series of precipitation tests for zinc are carried out: a 2{sup 2} full factorial design and a completely randomized factorial design. In these series the factors investigated are pH of solution during the precipitation and the amount of sodium sulphide added to precipitate zinc sulphide. The data of these tests are used to describe two empirical mathematical models for zinc and yttrium precipitation yields by regression analysis. The highest precipitation yields for zinc are obtained under the following conditions: pH equal to 2–2.5% and 10–12% v/v of Na{sub 2}S concentrated solution at 10% w/v. In these conditions the coprecipitation of yttrium is of 15–20%. Finally further yttrium precipitation experiments by oxalic acid on the residual solutions, after removing of zinc, show that yttrium could be recovered and calcined to obtain the final product as yttrium oxide. The achieved results allow to propose a CRT recycling process based on leaching of fluorescent powder from cathode ray tube and recovery of yttrium oxide after removing of zinc by precipitation. The final recovery of yttrium is 75–80%.

Iron filled carbon nanostructures from different precursors

International Nuclear Information System (INIS)

Costa, S.; Borowiak-Palen, E.; Bachmatiuk, A.; Ruemmeli, M.H.; Gemming, T.; Kalenczuk, R.J.

2008-01-01

Here, we present a study on the synthesis of different nanostructures with one single-step in situ filling (encapsulation) via carbon vapor deposition (CVD). Ferrocene, acetylferrocene and iron (II) nitrate as iron precursors were explored. The application of each of these compounds resulted in different carbon nanomaterials such as: iron filled multiwalled carbon nanotubes with a low filling ratio (Fe-MWCNT), iron filled nanocapsules and unfilled MWCNT. The as-produced samples were purified by high temperature annealing and acid treatment. The purified materials were characterised using transmission electron microscopy (TEM) and Raman spectroscopy

Integration of coagulation and adsorption for removal of N-nitrosodimethylamine (NDMA) precursors from biologically treated municipal wastewater.

Science.gov (United States)

Wang, Miaomiao; Meng, Yingjie; Ma, Defang; Wang, Yan; Li, Fengli; Xu, Xing; Xia, Chufan; Gao, Baoyu

2017-05-01

This study investigated the N-nitrosodimethylamine (NDMA) formation potential of various dissolved organic matter (DOM) fractions in biologically treated municipal wastewater by UF fractionation, XAD-8 resin adsorption isolation, and excitation and emission matrix (EEM) fluorescence spectroscopy. Removal of various NDMA precursor fractions was also analyzed to evaluate the efficiency of traditional water treatment processes (coagulation, adsorption, and coagulation-adsorption). Results showed that NDMA were mainly formed by low molecular weight (MW) fractions (NDMA formation potential (57%), followed by isolated adsorption treatment (50%) and isolated coagulation treatment (28%). The powdered activated carbon (PAC) adsorption process could reduce the high MW precursors (>30 kDa) by 48%, which was higher than other treatments. In contrast, the highest uptake (66%) of low MW precursors (<30 kDa) was achieved by the coagulation-adsorption process. All treatments preferentially removed the hydrophobic acids (HoA) fraction compared to other fractions. Coagulation could remove more fulvic acid-like substances and adsorption could remove more microbial by-products and aromatic proteins.

Oxidative Precipitation of Manganese from Acid Mine Drainage by Potassium Permanganate

Directory of Open Access Journals (Sweden)

Regeane M. Freitas

2013-01-01

Full Text Available Although oxidative precipitation by potassium permanganate is a widely recognised process for manganese removal, research dealing with highly contaminated acid mine drainage (AMD has yet to be performed. The present study investigated the efficiency of KMnO4 in removing manganese from AMD effluents. Samples of AMD that originated from inactive uranium mine in Brazil were chemically characterised and treated by KMnO4 at pH 3.0, 5.0, and 7.0. Analyses by Raman spectroscopy and geochemical modelling using PHREEQC code were employed to assess solid phases. Results indicated that the manganese was rapidly oxidised by KMnO4 in a process enhanced at higher pH. The greatest removal, that is, 99%, occurred at pH 7.0, when treated waters presented manganese levels as low as 1.0 mg/L, the limit established by the Brazilian legislation. Birnessite (MnO2, hausmannite (Mn3O4, and manganite (MnOOH were detected by Raman spectroscopy. These phases were consistently identified by the geochemical model, which also predicted phases containing iron, uranium, manganese, and aluminium during the correction of the pH as well as bixbyite (Mn2O3, nsutite (MnO2, pyrolusite (MnO2, and fluorite (CaF2 following the KMnO4 addition.

The use of radioactive precursors for the labeling of ribosomal proteins in Euglena

International Nuclear Information System (INIS)

Freyssinet, Georges

1977-01-01

The metabolism of three radioactive compounds has been studied in Euglena gracilis, either in the dark during the non-growing phase, or during light-induced greening, in the presence or absence of inhibitors of protein synthesis. The results can be summarized as follows: the fixation of 14 CO 2 and its incorporation into proteins occurs rapidly. Their intensities depend on the time of incubation and the physiological state of cells. Radioactive amino acids penetrate the cells within 2-4 hours and incorporation into proteins follows the uptake. In a few cases, amino acid uptake is low or even nonexistent. The rates of uptake and incorporation of radioactive sodium sulfate depend on the sulfur deficiency induced during growth in the dark, and on the time of incubation. Protein synthesis inhibitors act either on uptake or on incorporation or on both. The rate of inhibition depends on the inhibitor and precursor used. The radioactive precursors can be used for the labeling of cytoplasmic and chloroplast ribosomal proteins. The most favourable conditions for this labeling are mostly related to the uptake and incorporation measured on whole cells. All these results allow criteria to be determined which facilitate the choice of inhibitors, precursors and conditions of incubation depending on the protein studied

Effect of elicitors and precursors on azadirachtin production in hairy root culture of Azadirachta indica.

Science.gov (United States)

Srivastava, Smita; Srivastava, A K

2014-02-01

The present study involved strategies for enhancement in in vitro azadirachtin (commercially used biopesticide) production by hairy root cultivation of Azadirachta indica. Improvement in the azadirachtin production via triggering its biosynthetic pathway in plant cells was carried out by the exogenous addition of precursors and elicitors in the growth medium. Among the different abiotic stress inducers (Ag(+), Hg(+2), Co(+2), Cu(+2)) and signal molecules (methyl jasmonate and salicylic acid) tested, salicylic acid at 15 mg l(-1) of concentration was found to enhance the azadirachtin yield in the hairy roots to the maximum (up to 4.95 mg g(-1)). Similarly, among the different biotic elicitors tested (filter-sterilized fungal culture filtrates of Phoma herbarium, Alternaria alternata, Myrothecium sp., Fusarium solani, Curvularia lunata, and Sclerotium rolfsii; yeast extract; and yeast extract carbohydrate fraction), addition of filter-sterilized fungal culture filtrate of C. lunata (1 % v/v) resulted in maximum azadirachtin yield enhancement in hairy root biomass (up to 7.1 mg g(-1)) with respect to the control (3.3 mg g(-1)). Among all the biosynthetic precursors studied (sodium acetate, cholesterol, squalene, isopentynyl pyrophosphate, mavalonic acid lactone, and geranyl pyrophosphate), the overall azadirachtin production (70.42 mg l(-1) in 25 days) was found to be the highest with cholesterol (50 mg l(-1)) addition as an indirect precursor in the medium.

Precipitation of iron (III) using magnesium oxide in fluidized bed

International Nuclear Information System (INIS)

Esteban-Bocardo, P. A.; Ferreira-Rocha, S. D.

2006-01-01

A process for iron (III) removal by hydroxide precipitation from and acid synthetic inorganic effluent using magnesium oxide as an alternative precipitant agent in a fluidized bed was developed. An acid synthetic inorganic effluent containing 100 and 200 mg/l of ferric ions (pH=1.0) was continuously fed up to the acrylic column (30 cm high and 2 cm diameter) during 180 minutes. Magnesium oxide pulp (3% v/v) was injected at the beginning of the experiment in order to allow the iron hydroxides precipitation. The concentration and pH profiles agreed in their curves, while the pH profile rose,the concentration profile decreased and a high percentage of iron removal /higher to 99%) was reached. Extremely low iron concentrations have been reached, thus permitting to attend to the environmental standard of 10.0 mg/l for discharge of effluent containing ferric ions established by the law DN 10/86 of COPAM (Conselho de Politica Ambiental do Estado de Minas Gerais-Brazil). (Author)

Lanthanide-alkali double sulfate precipitation from strong sulfuric acid NiMH battery waste leachate.

Science.gov (United States)

Porvali, Antti; Wilson, Benjamin P; Lundström, Mari

2018-01-01

In NiMH battery leaching, rare earth element (REE) precipitation from sulfate media is often reported as being a result of increasing pH of the pregnant leach solution (PLS). Here we demonstrate that this precipitation is a phenomenon that depends on both Na + and SO 4 2- concentrations and not solely on pH. A two-stage leaching for industrially crushed NiMH waste is performed: The first stage consists of H 2 SO 4 leaching (2 M H 2 SO 4 , L/S = 10.4, V = 104 ml, T = 30 °C) and the second stage of H 2 O leaching (V = 100 ml, T = 25 °C). Moreover, precipitation experiments are separately performed as a function of added Na 2 SO 4 and H 2 SO 4 . During the precipitation, higher than stoichiometric quantities of Na to REE are utilized and this increase in both precipitation reagent concentrations results in an improved double sulfate precipitation efficiency. The best REE precipitation efficiencies (98-99%) - achieved by increasing concentrations of H 2 SO 4 and Na 2 SO 4 by 1.59 M and 0.35 M, respectively - results in a 21.8 times Na (as Na 2 SO 4 ) and 58.3 times SO 4 change in stoichiometric ratio to REE. Results strongly indicate a straightforward approach for REE recovery from NiMH battery waste without the need to increase the pH of PLS. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

Bound volatile precursors in genotypes in the pedigree of 'Marion' blackberry (Rubus sp.).

Science.gov (United States)

Du, Xiaofen; Finn, Chad E; Qian, Michael C

2010-03-24

Glycosidically bound volatiles and precursors in genotypes representing the pedigree for 'Marion' blackberry were investigated over two growing seasons. The volatile precursors were isolated using a C18 solid-phase extraction column. After enzymatic hydrolysis, the released volatiles were analyzed using stir bar sorptive extraction gas chromatography-mass spectrometry (GC-MS) and direct microvial insert thermal desorption GC-MS. The most abundant volatile precursors in the genotypes were alcohols, followed by shikimic acid derivatives. High amounts of furanone glycosides were also detected, while norisoprenoids only existed in a small amount in blackberries. The volatile precursor composition in the genotypes in the 'Marion' pedigree was very similar to their free volatile distribution. 'Logan' and 'Olallie' predominantly had bound norisoprenoids. Wild 'Himalaya' predominated with terpene alcohol and furaneol glycosides, whereas 'Santiam' and 'Chehalem' contained a high level of terpene alcohol glycosides. A similar inheritance pattern was also observed for some volatile precursors in the genotypes in the 'Marion' pedigree. A high content of linalool, hydroxylinalool, and alpha-ionol glycosides in 'Olallie' and a low content in 'Chehalem' resulted in a moderate level in their offspring 'Marion', while a low content of (E)-linalool oxide precursor in 'Olallie' and a high content in 'Chehalem' also resulted in a moderate level in 'Marion'. However, the concentration of furaneol glycosides in 'Marion' exceeded that of its two parents.

Adsorption of arsenic by iron rich precipitates from two coal mine drainage sites on the West Coast of New Zealand

International Nuclear Information System (INIS)

Rait, R.; Trumm, D.; Pope, J.; Craw, D.; Newman, N.; MacKenzie, H.

2010-01-01

Dissolved As can be strongly adsorbed to fine grained Fe(III) minerals such as hydroxides, oxyhydroxides and hydroxysulphates. Therefore precipitates that form during neutralisation or treatment of acid mine drainage have potential to be useful for treatment of As-contaminated water because acid mine drainage is often Fe rich. We tested the adsorption properties of Fe(III) rich precipitates from two West Coast coal mines with As-contaminated water from an historic gold ore processing site near Reefton. Precipitates were collected from distinctly different settings, an active acid mine drainage treatment plant at Stockton mine and the neutralisation/oxidation zone of acid mine drainage discharge at the abandoned Blackball Coal Mine. The two mine sites produce precipitates with different compositions and mineralogy. Arsenic adsorption onto precipitates from each site was determined in batch and column tests under laboratory conditions. Batch experiments indicate As adsorption occurs rapidly during the first 5 h and reaches equilibrium after 24 h. At equilibrium, and for a dosing ratio of 50 g of precipitate per litre of water, As concentrations decreased from 99 mg/L to 0.0080 mg/L with precipitates from Stockton and to 0.0017 mg/L with precipitates from Blackball. Arsenic adsorption capacity is up to 12 mg/g on precipitates from Stockton sludge and 74 mg/g on precipitates from Blackball. The Blackball precipitate adsorbs more As than precipitates from Stockton which is probably due to the higher Fe oxide content but pH and surface structure could also play a role. The column experiment confirmed that adsorption of As from a continuous waste stream onto these precipitates is possible, and that passive remediation using this waste product mixed with gravel to enhance permeability could be a viable approach at As-contaminated mine sites. (author). 56 refs., 10 figs., 6 tabs.

Precursors prior to type IIn supernova explosions are common: Precursor rates, properties, and correlations

Energy Technology Data Exchange (ETDEWEB)

Ofek, Eran O.; Steinbok, Aviram; Arcavi, Iair; Gal-Yam, Avishay; Tal, David; Ben-Ami, Sagi; Yaron, Ofer [Benoziyo Center for Astrophysics, Weizmann Institute of Science, 76100 Rehovot (Israel); Sullivan, Mark [School of Physics and Astronomy, University of Southampton, Southampton SO17 1BJ (United Kingdom); Shaviv, Nir J. [Racah Institute of Physics, The Hebrew University, 91904 Jerusalem (Israel); Kulkarni, Shrinivas R. [Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA 91125 (United States); Nugent, Peter E. [Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720 (United States); Kasliwal, Mansi M. [Observatories of the Carnegie Institution for Science, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Cenko, S. Bradley [Astrophysics Science Division, NASA/Goddard Space Flight Center, Mail Code 661, Greenbelt, MD 20771 (United States); Laher, Russ; Surace, Jason [Spitzer Science Center, California Institute of Technology, M/S 314-6, Pasadena, CA 91125 (United States); Bloom, Joshua S.; Filippenko, Alexei V. [Department of Astronomy, University of California, Berkeley, CA 94720-3411 (United States); Silverman, Jeffrey M. [Department of Astronomy, University of Texas, Austin, TX 78712 (United States)

2014-07-10

There is a growing number of Type IIn supernovae (SNe) which present an outburst prior to their presumably final explosion. These precursors may affect the SN display, and are likely related to poorly charted phenomena in the final stages of stellar evolution. By coadding Palomar Transient Factory (PTF) images taken prior to the explosion, here we present a search for precursors in a sample of 16 Type IIn SNe. We find five SNe IIn that likely have at least one possible precursor event (PTF 10bjb, SN 2010mc, PTF 10weh, SN 2011ht, and PTF 12cxj), three of which are reported here for the first time. For each SN we calculate the control time. We find that precursor events among SNe IIn are common: at the one-sided 99% confidence level, >50% of SNe IIn have at least one pre-explosion outburst that is brighter than 3 × 10{sup 7} L{sub ☉} taking place up to 1/3 yr prior to the SN explosion. The average rate of such precursor events during the year prior to the SN explosion is likely ≳ 1 yr{sup –1}, and fainter precursors are possibly even more common. Ignoring the two weakest precursors in our sample, the precursors rate we find is still on the order of one per year. We also find possible correlations between the integrated luminosity of the precursor and the SN total radiated energy, peak luminosity, and rise time. These correlations are expected if the precursors are mass-ejection events, and the early-time light curve of these SNe is powered by interaction of the SN shock and ejecta with optically thick circumstellar material.

Mathematical modeling of the formation of sedimentary acid precipitation in the atmosphere in view of the evaporation of moisture from their surface

Directory of Open Access Journals (Sweden)

Gvozdyakov Dmitry

2017-01-01

Full Text Available The article presents the results of numeric simulation of the formation of sedimentary acid precipitation in the atmosphere taking into account the evaporation of moisture from their surfaces. It is established that the joint condensation of vapors of sulfuric anhydride and water vapor, given the flow of solar energy and the evaporation process significantly slows the growth of drops. The possibility of achieving the underlying surface by the formed sediments is analyzed.

A new technique for production of yellow cake with double precipitation

International Nuclear Information System (INIS)

Li Jianhua; Zeng Yijun; Li Shangyuan; Kong Guiying

1997-01-01

The author presents a new technique for production of yellow cake with double precipitation, thus solving a series of problems for precipitating uranium with traditional double precipitation. The new technique can not only remove ferric ions and sulfate radicals but also make solid-liquid separation easy, utilize effectively the sulfuric acid produced in ferric ions precipitation process, and increase uranium concentration of leaching liquor. To take it as producing yellow cake will save investment, simplify operation, and cut down the consumption of raw materials and energies. It is more competitive than ion-exchange or solvent extraction in the process of extracting-purifying and preparing yellow cake

Direct observation of a non-isothermal crystallization process in precursor Li10GeP2S12 glass electrolyte

Science.gov (United States)

Tsukasaki, Hirofumi; Mori, Shigeo; Shiotani, Shinya; Yamamura, Hideyuki; Iba, Hideki

2017-11-01

Crystallization of a precursor Li10GeP2S12 (LGPS) glass electrolyte by heat treatment significantly improves its ionic conductivity. The LGPS crystalline phase obtained by heat treatment above 450 °C shows an ionic conductivity on the order of 10-2 S/cm. To clarify the correlation between the crystallization behavior of precursor LGPS glasses and ionic conductivity, we developed an observation technique to visualize precipitated nanocrystallites and a new method to evaluate the crystallization degree via transmission electron microscopy (TEM). In-situ TEM observation revealed that LGPS nanocrystallites precipitated above 450 °C and their size remained fundamentally intact during heating. That is, the crystallization behavior could be characterized by only the formation of LGPS nanocrystallites in an amorphous matrix. In addition, the crystallization degree was quantitatively evaluated from electron diffraction patterns. The crystallization degree remarkably increased at around 450 °C and reached more than 60% above 450 °C. Based on these results, a high ionic conductivity of approximately 1.0 × 10-2 S/cm was confirmed to be directly associated with the appearance of the LGPS crystalline phase.

A Drosophila gene encoding a protein resembling the human β-amyloid protein precursor

International Nuclear Information System (INIS)

Rosen, D.R.; Martin-Morris, L.; Luo, L.; White, K.

1989-01-01

The authors have isolated genomic and cDNA clones for a Drosophila gene resembling the human β-amyloid precursor protein (APP). This gene produces a nervous system-enriched 6.5-kilobase transcript. Sequencing of cDNAs derived from the 6.5-kilobase transcript predicts an 886-amino acid polypeptide. This polypeptide contains a putative transmembrane domain and exhibits strong sequence similarity to cytoplasmic and extracellular regions of the human β-amyloid precursor protein. There is a high probability that this Drosophila gene corresponds to the essential Drosophila locus vnd, a gene required for embryonic nervous system development

Polysialic acid modification of the synaptic cell adhesion molecule SynCAM 1 in human embryonic stem cell-derived oligodendrocyte precursor cells

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Sebastian Werneburg

2015-05-01

Full Text Available Oligodendrocyte precursor cells (OPCs are the progenitors of myelinating oligodendrocytes in brain development and repair. Successful myelination depends on the control of adhesiveness during OPC migration and axon contact formation. The decoration of cell surface proteins with the glycan polysialic acid (polySia is a key regulatory element of OPC interactions during development and under pathological conditions. By far the major protein carrier of polySia is the neural cell adhesion molecule NCAM, but recently, polysialylation of the synaptic cell adhesion molecule SynCAM 1 has been detected in the developing mouse brain. In mice, polySia-SynCAM 1 is associated with cells expressing NG2, a marker of a heterogeneous precursor cell population, which is the primary source for oligodendrocytes in development and myelin repair but can also give rise to astrocytes and possibly neurons. It is not yet clear if polySia-SynCAM 1 is expressed by OPCs and its occurrence in humans is elusive. By generating uniform human embryonic stem cell-derived OPC cultures, we demonstrate that polySia is present on human OPCs but down-regulated during differentiation into myelin basic protein-positive oligodendrocytes. PolySia on NCAM resides on the isoforms NCAM-180 and NCAM-140, and SynCAM 1 is identified as a novel polySia acceptor in human OPCs.

Synchrotron X-ray induced solution precipitation of nanoparticles

CERN Document Server

Lee, H J; Hwu, Y; Tsai, W L

2003-01-01

By irradiating a solution in electroless Ni deposition using synchrotron X-rays, Ni composite was found to nucleate homogeneously and eventually precipitate in the form of nanoparticles. The size of the nanoparticles precipitated is rather uniform (100-300 nm depending on the applied temperature). By the addition of an organic acid, well-dispersed nanoparticles could be effectively deposited on glass substrate. The hydrated electrons (e sub a sub q sup -), products of radiolysis of water molecules by synchrotron X-rays, may be responsible for the effective reduction of the metal ions, resulting in homogeneous nucleation and nanoparticle formation. Our results suggest that synchrotron X-ray can be used to induce solution precipitation of nanoparticles and therefore lead to a new method of producing nanostructured particles and coating.

Preparation of porous carboxymethyl chitosan grafted poly (acrylic acid) superabsorbent by solvent precipitation and its application as a hemostatic wound dressing

Energy Technology Data Exchange (ETDEWEB)

Chen, Yu, E-mail: cylsy@163.com [School of Material Science and Engineering, Beijing Institute of Technology, Beijing 100081 (China); Zhang, Yong [School of Life Science, Beijing Institute of Technology, Beijing 100081 (China); Wang, Fengju [School of Material Science and Engineering, Beijing Institute of Technology, Beijing 100081 (China); Meng, Weiwei; Yang, Xinlin [School of Life Science, Beijing Institute of Technology, Beijing 100081 (China); Li, Peng [School of Material Science and Engineering, Beijing Institute of Technology, Beijing 100081 (China); Jiang, Jianxin [State Key Laboratory of Trauma Burns and Combined Injury, The Third Military Medical University, Chongqing 400042 (China); Tan, Huimin [School of Material Science and Engineering, Beijing Institute of Technology, Beijing 100081 (China); Zheng, Yongfa [Guangdong Fuyang Biotechnology Co., Ltd., Heyuan, Guangdong 517000 (China)

2016-06-01

The volume phase transition of a hydrogel initiated by shrinking may result in complex patterns on its surface. Based on this unique property of hydrogel, we have developed a novel solvent precipitation method to prepare a kind of novel superabsorbent polymers with excellent hemostatic properties. A porous carboxymethyl chitosan grafted poly (acrylic acid) (CMCTS-g-PAA) superabsorbent polymer was prepared by precipitating CMCTS-g-PAA hydrogel with ethanol. Its potential application in hemostatic wound dressing was investigated. The results indicate that the modified superabsorbent polymer is non-cytotoxic. It showed a high swelling capacity and better hemostatic performance in the treatments of hemorrhage model of ear artery, arteria cruralis and spleen of the New Zealand white rabbit than the unmodified polymer and other commonly used clinic wound dressings. The hemostatic mechanism of the porous CMCTS-g-PAA polymer was also discussed. - Highlights: • The novel solvent precipitation method was developed to prepare the porous superabsorbent polymer. • The swelling rate was promoted and the harmful residual monomer was leached after modification. • The modified polymer showed good biological safety. • It showed good hemostasis to arterial hemorrhage model of the animal. • The hemostatic mechanism of the modified superabsorbent polymer was discussed.

Intestinal levels of anandamide and oleoylethanolamide in food-deprived rats are regulated through their precursors

DEFF Research Database (Denmark)

Petersen, Gitte; Sørensen, Camilla; Schmid, Patricia C

2006-01-01

The anorectic lipid oleoylethanolamide and the orexigenic lipid anandamide both belong to the group of N-acylethanolamines that are generated by the enzyme N-acylphosphatidylethanolamine-hydrolyzing phospholipase D. The levels of the two bioactive lipids were investigated in rat intestines after 24...... h of starvation as well as after 1 and 4 h of re-feeding. Total levels of precursor phospholipids and N-acylethanolamines were decreased upon food-deprivation whereas the level of the anandamide precursor molecule was significantly increased. The level of 2-arachidonoyl-glycerol was unchanged...... as was the activity of N-acyltransferase, N-acylphosphatidylethanolamine-hydrolyzing phospholipase D, and fatty acid amide hydrolase upon starvation and re-feeding. It is concluded that remodeling of the amide-linked fatty acids of N-acylphosphatidylethanolamine is responsible for the opposite effects on levels...

Characterization of CaSn(OH6 and CaSnO3 Nanostructures Synthesized by a New Precursor

Directory of Open Access Journals (Sweden)

S. Moshtaghi

2015-04-01

Full Text Available In this paper, calcium stannate nanoparticles were synthesized by a fast and simple co-precipitation procedure. For CaSnO3 preparation ammonia was used as precipitation agent. The effect of various surfactants such as cationic, anionic and neutral on the morphology of the products was investigated. By changing in Ca(Sal2 as a new precursor different morphologies were obtained. Ligand as a capping agent with steric hindrance leads to preparation of product with lower particle size. These semiconductor nanostructures have photo-catalyst activities and can degrade organic dyes as water pollution. The synthesized materials were characterized by X-ray diffraction (XRD technique, scanning electron microscopy (SEM Fourier transform infrared (FT-IR and UV-visible spectroscopy.

Influence of Pd-precursor on the acetoxylation activity of Pd-Sb/TiO{sub 2} catalysts

Energy Technology Data Exchange (ETDEWEB)

Ben-homeid, A. [Benghazi Univ. (Libyan Arab Jamahiriya). Chemistry Dept.; Kalevaru, V.N.; Radnik, J.; Luecke, B.; Martin, A. [Leibniz-Institut fuer Katalyse e.V. an der Universitaet Rostock (Germany)

2013-11-01

The impact of palladium precursors (e.g. chloride-PdCl{sub 2}; acetate-Pd(OAc){sub 2}; nitrate-Pd(NO{sub 3}){sub 2}) on the catalytic properties of Pd-Sb/TiO{sub 2} catalysts used for acetoxylation of toluene has been investigated. The catalysts were characterized by different techniques such as N{sub 2}-adsorption (BET-surface area and pore volume), XRD, TEM, CO-Chemisorption and XPS for better understanding of the catalytic properties of the catalysts. The acetate and nitrate-type precursors exhibited higher surface areas, pore volumes and higher dispersion of Pd, but displayed poor performance compared to chloride precursor. TEM analysis indicated that the size of Pd particles depended upon the nature of Pd-precursor. Among the three, chloride precursor exhibited bigger Pd particles. XPS results revealed that all the fresh catalysts irrespective of Pd-precursor contained Pd in oxidized state (i.e. Pd{sup +2}), while in the spent catalysts such oxidized Pd species were reduced. The catalytic performance was found to depend strongly on the nature of precursor used. Among the three, the catalysts prepared from chloride-type precursor showed much higher overall catalytic activity (68%) than those of nitrate and/or acetate type precursors. Moreover, these two precursors (acetate and nitrate) gave higher total oxidation products due to oxidative decomposition of mainly acetic acid. Furthermore, the catalyst prepared from Cl-precursor revealed easy deactivation due to coke deposition and also due to loss of Pd in the near-surface-region. (orig.)

Cyclization during synthetic studies on necic acids and their precursors

International Nuclear Information System (INIS)

Drewes, S.E.; Emslie, N.D.; Pitchford, A.T.; Wallace, B.W.

1982-01-01

The synthesis of macrocyclic diesters which incorporate one of the necic acids, retronecic acid, is described. Instances are also cited of the formation of 'unwanted' cyclic products which result during interconversion of certain intermediates used in the synthesis of necic acids. The mechanism of formation of these products serves to highlight interesting aspects of the reactivity of the intermediates

Cs separation from nitric acid solutions of radioactive waste

International Nuclear Information System (INIS)

Heckmann, K.; Pieronczyk, W.; Strnad, J.; Feldmaier, F.

1989-01-01

It was the objective of this study to selectively separate active caesium (Cs-134 and Cs-137) from acid radioactive waste solutions (especially MAW and HAWC). The following 'strategy' was designed for a separation process: synthesis of reagents which are acid-resistant and selective for caesium; precipitation of Cs + and separation of the precipitates by filtration or centrifugation or precipitation of Cs + and separation of the precipitates by flotation; caesium separation by liquid-liquid extraction. As precipitating agents, sodium tetraphenylborate (kalignost) and several of its fluorine derivatives were examined. (orig./RB) [de

Research and performance evaluation on an HA integrated acid system for sandstone acidizing

Directory of Open Access Journals (Sweden)

Liqiang Zhao

2018-03-01

Full Text Available When the conventional sandstone acidizing technologies are adopted, many slugs are needed in the injection of prepad fluid, treatment fluid and postpad fluid, and consequently the production and operation suffers inconveniences and difficulties. In view of this, a kind of HA integrated acid system which is mainly composed of organic polybasic acids (HA+HCl + HF and an efficient organic solvent was developed in this paper based on the idea of integrated acid replacing ''multiple steps'' and high efficiency and intensification. Via this HA integrated acid system, the complicated blockage in sandstone reservoirs can be removed effectively. Then, experiments were carried out on this system to evaluate its performance in terms of its retardance, organic blockage dissolution, chelating and precipitation inhibition. It is indicated that this new system can not only realize the acidizing of conventional integrated acid, but also present a good retarding performance by controlling H+ multi-stage ionization step by step and by forming silica acid-aluminum phosphonate film on the surface of clay minerals; that via this new HA integrated acid system, the organic blockage can be removed efficiently; and that it is wider in pH solution range than conventional APCs (aminopolycarboxyliates chelants, stronger in chelating capacity of Ca2+, Mg2+ and Fe3+ than conventional chelants (e.g. EDTA, NTA and DTPA, and better in precipitation inhibition on metal fluoride, fluosilicic acid alkali metal, fluoaluminic acid alkali metal and hydroxide than multi-hydrogen acid, fluoboric acid and mud acid systems. These research results provide a technical support for the plugging removal in high-temperature deep oil and gas reservoirs. Keywords: Organic polybasic acid, Integrated acid, Retardance, Chelating, Precipitation, Acidizing, Sandstone, Reservoir

Moessbauer study of CO-precipitated Fischer-Tropsch iron catalysts

International Nuclear Information System (INIS)

Rao, K.R.P.M.; Huggins, F.E.; Mahajan, V.; Huffman, G.P.; Bukur, D.B.; Rao, V.U.S.

1994-01-01

Moessbauer spectroscopy studies of precipitated Fischer-Tropsch (FT) iron catalysts, viz. 100 Fe/5 Cu/4.2 K/x SiO 2 , where x = 0, 8, 16, 24, 25, 40, or 100, have shown that reduction of the oxide precursor in CO gives rise to χ-carbide Fe 5 C 2 whose amount decreases with an increase of SiO 2 content. The χ-carbide is converted into magnetite Fe 3 O 4 while catalyzing the FT synthesis reaction. A correlation between FT activity and the content of χ-carbide in the catalysts was found, which indicated that χ-carbide is active for FT synthesis reaction. (orig.)

Characterization of the precipitates formed during the denitration of simulated HRLW

International Nuclear Information System (INIS)

Music, S.; Ristic, M.; Popovic, S.

1989-01-01

The denitration of several chemical compositions of simulated highly radioactive liquid waste (HRLW) was performed using formic acid as reducing agent. Precipitates formed during the denitration of simulated HRLW were analyzed using x-ray diffraction and 57 Fe Moessbauer spectroscopy. Goethite and amorphous fractions were the principal phases in these precipitates. It was found that the chemical composition of HRLW and the experimental conditions of denitration had more influence on the crystal formation and the particle size than on the phase composition of the precipitates. (author) 27 refs.; 6 figs.; 6 tabs

Biosynthethesis of dipicolinic acid in Clostridium roseum

International Nuclear Information System (INIS)

Prakasan, K.M.; Sharma, D.; Gollakota, K.G.; Lakechaura, B.D.

1975-01-01

Dipicolinic acid (DPA) is a major constituent of bacterial endospores and the thermal resistance of spores is closely correlated with their calcium dipicolinate content. The biosynthesis of DPA in anaerobes was studied in Cl. roseum using the technique of endotrophic sporulation. The cells from the complex medium were harvested at a stage when they were refractile and stainable, resuspended in nongrowth promoting mineral water supplemented with radioactive presumptive precursors of DPA and incubated. The incorporation in DPA of exogenously supplied individual metabolites was followed by radioactictivity (C 14 ) measurements. Glutamic acid, aspartic acid, alanine, serine, and acetate were found efficient precursors of DPA. (author)

Whither Acid Rain?

Directory of Open Access Journals (Sweden)

Peter Brimblecombe

2000-01-01

Full Text Available Acid rain, the environmental cause célèbre of the 1980s seems to have vanished from popular conscience. By contrast, scientific research, despite funding difficulties, has continued to produce hundreds of research papers each year. Studies of acid rain taught much about precipitation chemistry, the behaviour of snow packs, long-range transport of pollutants and new issues in the biology of fish and forested ecosystems. There is now evidence of a shift away from research in precipitation and sulfur chemistry, but an impressive theoretical base remains as a legacy.

Primary structure of the precursor for the anthozoan neuropeptide Antho-RFamide from Renilla köllikeri: Evidence for unusual processing enzymes

DEFF Research Database (Denmark)

Reinscheid, R K; Grimmelikhuijzen, C J

1994-01-01

distributed over the precursor protein. Of the 36 Antho-RFamide sequences, 29 copies are separated by the five amino acid spacer sequence Arg-Glu/Gly-Asn/Ser/Asp-Glu/Lys-Glu. This implicates processing at single Arg and single Glu residues. Endoproteolytic cleavage at the C-terminal side of paired or single......, and possibly also at other residues, and thus liberate all Antho-RFamide sequences. The processing of one precursor molecule probably yields 38 neuropeptides.(ABSTRACT TRUNCATED AT 250 WORDS)...... basic residues is a well known initial step in the maturation of precursor proteins. Cleavage at the C-terminal side of acidic residues, however, is unusual and must be catalyzed by a new type of processing enzyme. This processing enzyme is most likely to be an endoprotease, because the simplest way...

Complete covalent structure of statherin, a tyrosine-rich acidic peptide which inhibits calcium phosphate precipitation from human parotid saliva.

Science.gov (United States)

Schlesinger, D H; Hay, D I

1977-03-10

The complete amino acid sequence of human salivary statherin, a peptide which strongly inhibits precipitation from supersaturated calcium phosphate solutions, and therefore stabilizes supersaturated saliva, has been determined. The NH2-terminal half of this Mr=5380 (43 amino acids) polypeptide was determined by automated Edman degradations (liquid phase) on native statherin. The peptide was digested separately with trypsin, chymotrypsin, and Staphylococcus aureus protease, and the resulting peptides were purified by gel filtration. Manual Edman degradations on purified peptide fragments yielded peptides that completed the amino acid sequence through the penultimate COOH-terminal residue. These analyses, together with carboxypeptidase digestion of native statherin and of peptide fragments of statherin, established the complete sequence of the molecule. The 2 serine residues (positions 2 and 3) in statherin were identified as phosphoserine. The amino acid sequence of human salivary statherin is striking in a number of ways. The NH2-terminal one-third is highly polar and includes three polar dipeptides: H2PO3-Ser-Ser-H2PO3-Arg-Arg-, and Glu-Glu-. The COOH-terminal two-thirds of the molecule is hydrophobic, containing several repeating dipeptides: four of -Gn-Pro-, three of -Tyr-Gln-, two of -Gly-Tyr-, two of-Gln-Tyr-, and two of the tetrapeptide sequence -Pro-Tyr-Gln-Pro-. Unusual cleavage sites in the statherin sequence obtained with chymotrypsin and S. aureus protease were also noted.

DEGREE OF ACIDIFICATION OF PRECIPITATION IN BIELSKO-BIAŁA REGION

Directory of Open Access Journals (Sweden)

Henryk Kasza

2014-10-01

Full Text Available In the paper results of long-term studies on acidification of water precipitation conducted in seven research points located near Bielsko-Biała were introduced. In each point period of study lasted ca. 1 year. The research was performed in the years 2002-2010. The range of pH of precipitation varied between 3.35 to 7.22. Majority of precipitation samples, because approximately 86% had pH < 5.6 i.e. lower than natural level, which indicated the presence of acidifying substances. Amongst samples of precipitation 47.6% were significantly and strongly acidic i.e. pH < 4.5. The rainwater with pH < 5.6 was more frequent than in more industrialized part of Silesian voivodship. In the investigated area pH of precipitation is mainly under influence of pollution flowing from west and southern-west and local sources of its emission.

Development of techniques for tagging precursor and essential chemicals

Energy Technology Data Exchange (ETDEWEB)

Swansiger, W.A.; Shepodd, T.J. [Sandia National Labs., Livermore, CA (United States); Phillips, M.L.F. [Sandia National Labs., Albuquerque, NM (United States)

1994-01-01

The ability to identify the manufacturers and distributors of chemicals seized in raids of illicit drug labs would be of great value in controlling the diversion of these chemicals. We developed a tagging scheme based on the addition of sub-ppM concentrations of various combinations of rare-earth elements to the target chemicals and evaluated a number of techniques for detecting the tags. We developed soluble tags for tagging liquids and selected Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) as the preferred detection technique. We developed insoluble tags for tagging solids and developed methods to analyze them and mix them into solid precursors. We have successfully demonstrated the tagging of several solvents and two of the precursor chemicals used in one of the most popular clandestine methamphetamine syntheses (ephedrine reacting with hydriodic acid/red phosphorus). The tagging scheme is capable of yielding tens of thousands of signatures (using holmium as an internal standard and up to 9 rare-earths at up to 3 concentrations yields 3{sup 9} {minus} 1 = 19,682 signatures) and is applicable to most of the chemicals on the precursor and essential chemicals list. In the concentrations employed, the tags are safe enough to be added to pharmaceuticals and cheap enough to tag tanker loads of chemicals.

Natural Organochlorines as Precursors of 3-Monochloropropanediol Esters in Vegetable Oils.

Science.gov (United States)

Tiong, Soon Huat; Saparin, Norliza; Teh, Huey Fang; Ng, Theresa Lee Mei; Md Zain, Mohd Zairey Bin; Neoh, Bee Keat; Md Noor, Ahmadilfitri; Tan, Chin Ping; Lai, Oi Ming; Appleton, David Ross

2018-01-31

During high-temperature refining of vegetable oils, 3-monochloropropanediol (3-MCPD) esters, possible carcinogens, are formed from acylglycerol in the presence of a chlorine source. To investigate organochlorine compounds in vegetable oils as possible precursors for 3-MCPD esters, we tested crude palm, soybean, rapeseed, sunflower, corn, coconut, and olive oils for the presence of organochlorine compounds. Having found them in all vegetable oils tested, we focused subsequent study on oil palm products. Analysis of the chlorine isotope mass pattern exhibited in high-resolution mass spectrometry enabled organochlorine compound identification in crude palm oils as constituents of wax esters, fatty acid, diacylglycerols, and sphingolipids, which are produced endogenously in oil palm mesocarp throughout ripening. Analysis of thermal decomposition and changes during refining suggested that these naturally present organochlorine compounds in palm oils and perhaps in other vegetable oils are precursors of 3-MCPD esters. Enrichment and dose-response showed a linear relationship to 3-MCPD ester formation and indicated that the sphingolipid-based organochlorine compounds are the most active precursors of 3-MCPD esters.

The effects of borate minerals on the synthesis of nucleic acid bases, amino acids and biogenic carboxylic acids from formamide.

Science.gov (United States)

Saladino, Raffaele; Barontini, Maurizio; Cossetti, Cristina; Di Mauro, Ernesto; Crestini, Claudia

2011-08-01

The thermal condensation of formamide in the presence of mineral borates is reported. The products afforded are precursors of nucleic acids, amino acids derivatives and carboxylic acids. The efficiency and the selectivity of the reaction was studied in relation to the elemental composition of the 18 minerals analyzed. The possibility of synthesizing at the same time building blocks of both genetic and metabolic apparatuses, along with the production of amino acids, highlights the interest of the formamide/borate system in prebiotic chemistry.

Catalyst of a metal heteropoly acid salt that is insoluble in a polar solvent on a non-metallic porous support and method of making

Science.gov (United States)

Wang, Yong [Richland, WA; Peden, Charles H. F. [West Richland, WA; Choi, Saemin [Richland, WA

2002-10-29

The present invention includes a catalyst having (a) a non-metallic support having a plurality of pores; (b) a metal heteropoly acid salt that is insoluble in a polar solvent on the non-metallic support; wherein at least a portion of the metal heteropoly acid salt is dispersed within said plurality of pores. The present invention also includes a method of depositing a metal heteropoly acid salt that is insoluble in a polar solvent onto a non-metallic support having a plurality of pores. The method has the steps of: (a) obtaining a first solution containing a first precursor of a metal salt cation; (b) obtaining a second solution containing a second precursor of a heteropoly acid anion in a solvent having a limited dissolution potential for said first precursor; (c) impregnating the non-metallic support with the first precursor forming a first precursor deposit within the plurality of pores, forming a first precursor impregnated support; (d) heating said first precursor impregnated support forming a bonded first precursor impregnated support; (e) impregnating the second precursor that reacts with the precursor deposit and forms the metal heteropoly acid salt.

A single-source solid-precursor method for making eco-friendly doped semiconductor nanoparticles emitting multi-color luminescence.

Science.gov (United States)

Manzoor, K; Aditya, V; Vadera, S R; Kumar, N; Kutty, T R N

2007-02-01

A novel synthesis method is presented for the preparation of eco-friendly, doped semiconductor nanocrystals encapsulated within oxide-shells, both formed sequentially from a single-source solid-precursor. Highly luminescent ZnS nanoparticles, in situ doped with Cu(+)-Al3+ pairs and encapsulated with ZnO shells are prepared by the thermal decomposition of a solid-precursor compound, zinc sulfato-thiourea-oxyhydroxide, showing layered crystal structure. The precursor compound is prepared by an aqueous wet-chemical reaction involving necessary chemical reagents required for the precipitation, doping and inorganic surface capping of the nanoparticles. The elemental analysis (C, H, N, S, O, Zn), quantitative estimation of different chemical groups (SO4(2-) and NH4(-)) and infrared studies suggested that the precursor compound is formed by the intercalation of thiourea, and/or its derivatives thiocarbamate (CSNH2(-)), dithiocarbamate (CS2NH2(-)), etc., and ammonia into the gallery space of zinc-sulfato-oxyhydroxide corbel where the Zn(II) ions are both in the octahedral as well as tetrahedral coordination in the ratio 3 : 2 and the dopant ions are incorporated within octahedral voids. The powder X-ray diffraction of precursor compound shows high intensity basal reflection corresponding to the large lattice-plane spacing of d = 11.23 angstroms and the Rietveld analysis suggested orthorhombic structure with a = 9.71 angstroms, b = 12.48 angstroms, c = 26.43 angstroms, and beta = 90 degrees. Transmission electron microscopy studies show the presence of micrometer sized acicular monocrystallites with prismatic platy morphology. Controlled thermolysis of the solid-precursor at 70-110 degrees C leads to the collapse of layered structure due to the hydrolysis of interlayer thiourea molecules or its derivatives and the S2- ions liberated thereby reacts with the tetrahedral Zn(II) atoms leading to the precipitation of ZnS nanoparticles at the gallery space. During this process

In Vivo Roles of Fatty Acid Biosynthesis Enzymes in Biosynthesis of Biotin and α-Lipoic Acid in Corynebacterium glutamicum.

Science.gov (United States)

Ikeda, Masato; Nagashima, Takashi; Nakamura, Eri; Kato, Ryosuke; Ohshita, Masakazu; Hayashi, Mikiro; Takeno, Seiki

2017-10-01

For fatty acid biosynthesis, Corynebacterium glutamicum uses two type I fatty acid synthases (FAS-I), FasA and FasB, in addition to acetyl-coenzyme A (CoA) carboxylase (ACC) consisting of AccBC, AccD1, and AccE. The in vivo roles of the enzymes in supplying precursors for biotin and α-lipoic acid remain unclear. Here, we report genetic evidence demonstrating that the biosynthesis of these cofactors is linked to fatty acid biosynthesis through the FAS-I pathway. For this study, we used wild-type C. glutamicum and its derived biotin vitamer producer BFI-5, which was engineered to express Escherichia coli bioBF and Bacillus subtilis bioI Disruption of either fasA or fasB in strain BFI-5 led to decreased production of biotin vitamers, whereas its amplification contributed to increased production, with a larger impact of fasA in both cases. Double disruptions of fasA and fasB resulted in no biotin vitamer production. The acc genes showed a positive effect on production when amplified simultaneously. Augmented fatty acid biosynthesis was also reflected in pimelic acid production when carbon flow was blocked at the BioF reaction. These results indicate that carbon flow down the FAS-I pathway is destined for channeling into the biotin biosynthesis pathway, and that FasA in particular has a significant impact on precursor supply. In contrast, fasB disruption resulted in auxotrophy for lipoic acid or its precursor octanoic acid in both wild-type and BFI-5 strains. The phenotypes were fully complemented by plasmid-mediated expression of fasB but not fasA These results reveal that FasB plays a specific physiological role in lipoic acid biosynthesis in C. glutamicum IMPORTANCE For the de novo biosynthesis of fatty acids, C. glutamicum exceptionally uses a eukaryotic multifunctional type I fatty acid synthase (FAS-I) system comprising FasA and FasB, in contrast to most bacteria, such as E. coli and B. subtilis , which use an individual nonaggregating type II fatty acid synthase

Cervical digital photography for screening of uterine cervix cancer and its precursor lesions in developing countries.

Science.gov (United States)

Hillmann, Elise de Castro; Dos Reis, Ricardo; Monego, Heleusa; Appel, Márcia; Hammes, Luciano Serpa; Rivoire, Waldemar Augusto; Capp, Edison

2013-07-01

This study aims to evaluate and to compare the performance of cervical digital photography (CDP) to the visual inspection with acetic acid (VIA) and visual inspection with Lugol's iodine (VILI) methods for screening the uterine cervix cancer and its precursor lesions in developing countries. A cross-sectional study was performed in Brazil. 176 women were evaluated by VIA, VILI, CDP with acetic acid and CDP with Lugol's iodine. Kappa statistic was used to estimate the interobserver and intermethod agreement. Sensitivity, specificity and diagnostic accuracy of the four methods (VIA, VILI, CDP with acetic acid, CDP with Lugol's iodine) was calculated. Interobserver agreement for CDP with acetic acid was K = 0.441 and for CDP with Lugol's iodine was K = 0.533; intermethod agreement of VIA and CDP with acetic acid, K = 0.559; and of VILI and CDP with Lugol's iodine, K = 0.507. Sensitivity and specificity of CDP with acetic acid were 84.00 and 95.83 %, and of CDP with Lugol's iodine were 88.00 and 97.26 %, respectively. The diagnostic accuracy of CDP with acetic acid and CDP with Lugol's iodine was 92.78 and 94.90 %, respectively. This was the first study to assess the CDP with Lugol's iodine performance, which had similar performance to the CDP with acetic acid. CDP is considered a promising method for screening the uterine cervix cancer and its precursor lesions in developing countries.

Acidic deposition in California: findings from a program of monitoring and effects research

Energy Technology Data Exchange (ETDEWEB)

Takemoto, B.K.; Croes, B.E.; Brown, S.M.; Motallebi, N.; Westerdahl, F.D.; Margolis, H.G.; Cahill, B.T.; Mueller, M.D.; Holmes, J.R. [California Environmental Protection Agency, Sacramento, CA (United States). Research Division

1995-12-01

California`s 14-year, 25 million dollar acidic deposition program has studied the causes and effects of acidic air pollutants. In contrast to the eastern United States where sulfur-derived (S-derived) by-products from coal combustion dominate precipitation chemistry, nitrogen-derived (N-derived) acids predominate in wet and dry deposition in California. Adverse effects on the human lung have not been observed after short-term exposures to acidity, but extended exposures to ambient acidity may pose a chronic risk. No irreversible, adverse effects on surface waters in the Sierra Nevada mountain range or to the state`s forests have been found due to extent acidic inputs. The longer-term outlook for forests is less certain because the impacts observed elsewhere occurred after decades of S and N deposition, but at lower ambient ozone levels. Ozone is the major air pollutant stressor for forests, but atmospheric N has the potential to cause adverse changes in soil nutrient cycling. Impacts on man-made materials in southern California (e.g. galvanized steel) were found to be minor. While California does not have an ambient air quality standard for acidic air pollutants, emission of precursors have declined since the 1960s due to changes in industrial practices, improvements in technology and adoption of control measures for ozone. Lowering emission from motor vehicles will be emphasized to prevent future increases in N deposition. 67 refs., 4 figs., 2 tabs.

Process for recovering yttrium and lanthanides from wet-process phosphoric acid

Energy Technology Data Exchange (ETDEWEB)

Janssen, J.A.; Weterings, C.A.

1983-06-28

Process for recovering yttrium and lanthanides from wet-process phosphoric acid by adding a flocculant to the phosphoric acid, separating out the resultant precipitate and then recovering yttrium and lanthanides from the precipitate. Uranium is recovered from the remaining phosphoric acid.

Synthesis and structure of porous alumina precursors derived from n-alkylamine-AlCl3 system; Chokusa alkylamine-AlCl{sub 3} kei wo mochiiru takoshitsu alumina zenkutai no gosei to kozo

Energy Technology Data Exchange (ETDEWEB)

Yoshimura, M.; Machida, M.; Kijima, T. [Miyazaki Univ. (Japan)

1998-06-01

Alumina precursors have been prepared from AlCl3 by using n-alkylamines (C{sub n}H{sub 2n+1}NH2) as precipitant at pH 9.6 and pH 6.2, and the structure, composition, microstructure, and thermal decomposition behavior are investigated. The effects of the structure of the precursor on the decomposition behavior and on the surface area of porous alumina are also investigated. When alkylamines n{>=}6 are used, long periodicity phases are produced corresponding to larger than d=2.0nm spacing which can not be attributed to bayerite or pseudo-boehnite. Long periodicity phase is formed uniquely near the water content of about 50mass% (H2O/Al=4.5), and the spacing varies depending on the alkyl chainlength of amine. When the precipitate prepared at pH 6.2 is heated, water is desorbed at near 100degC, pseudo-baehnite phase is pyrolyzed at 300degC, and the precipitate changed into {gamma}-alumina at temperatures higher than 500degC. 16 refs., 9 figs.

Speciation and precipitation of heavy metals in high-metal and high-acid mine waters from the Iberian Pyrite Belt (Portugal).

Science.gov (United States)

Durães, Nuno; Bobos, Iuliu; da Silva, Eduardo Ferreira

2017-02-01

Acid mine waters (AMW) collected during high- and low-flow water conditions from the Lousal, Aljustrel, and São Domingos mining areas (Iberian Pyrite Belt) were physicochemically analyzed. Speciation calculation using PHREEQC code confirms the predominance of Me n+ and Me-SO 4 species in AMW samples. Higher concentration of sulfate species (Me-SO 4 ) than free ion species (Me n+ , i.e., Al, Fe, and Pb) were found, whereas opposite behavior is verified for Mg, Cu, and Zn. A high mobility of Zn than Cu and Pb was identified. The sulfate species distribution shows that Fe 3+ -SO 4 2- , SO 4 2- , HSO 4 - , Al-SO 4 , MgSO 4 0 , and CaSO 4 0 are the dominant species, in agreement with the simple and mixed metal sulfates and oxy-hydroxysulphates precipitated from AMW. The saturation indices (SI) of melanterite and epsomite show a positive correlation with Cu and Zn concentrations in AMW, which are frequently retained in simple metal sulfates. Lead is well correlated with jarosite and alunite (at least in very acid conditions) than with simple metal sulfates. The Pb for K substitution in jarosite occurs as increasing Pb concentration in solution. Lead mobility is also controlled by anglesite precipitation (a fairly insoluble sulfate), where a positive correlation was ascertained when the SI approaches equilibrium. The zeta potential of AMW decreased as pH increased due to colloidal particles aggregation, where water species change from SO 4 2- to OH - species during acid to alkaline conditions, respectively. The AMW samples were supersaturated in schwertmannite and goethite, confirmed by the Me n+ -SO 4 , Me n+ -Fe-O-OH, or Me n+ -S-O-Fe-O complexes identified by attenuated total reflectance infrared spectroscopy (ATR-IR). The ATR-IR spectrum of an AMW sample with pH 3.5 (sample L1) shows well-defined vibration plans attributed to SO 4 tetrahedron bonded with Fe-(oxy)hydroxides and the Me n+ sorbed by either SO 4 or Fe-(oxy)hydroxides. For samples with lower pH values (p

Chemical composition of precipitation in a forest area of Chongqing, southwest China

International Nuclear Information System (INIS)

Zhang, F.; Zhang, J.; Zhang, H.; Ogura, N.; Ushikubo, A.

1996-01-01

Experiments were carried out in Chongqing - a city seriously damaged by acid precipitation in southwest China - to explore chemical compositions of open bulk precipitation, throughfall and stemflow in a Masson pine (Pinus massoniana) forest. The results showed that annual mean pH values of and annual ion depositions in the three types of rain water were 4.47 and 50.6 g m -2 , 3.82 and 69.7 g m -2 m and 2.92 and 0.215 g m -2 respectively. pH values demonstrated an obvious seasonal variation; they were lower in winter than in the rest of the year. Ca 2+ and NH 4 + together made up more than 80% of the total cation, while SO 4 2- alone contributed over 90% to the total anion. This high level of SO 4 2- in rain water in Congqing, which outran those found in other cities in China, was closely related to the combustion of locally produced coal that contains 3 to 5% sulphur. Thus, acid precipitation in Chongqing is of a typical sulphuric-acid type. 6 refs., 3 figs., 6 tabs

Fabrication of superconducting wire using organometallic precursors and infiltration

International Nuclear Information System (INIS)

Lee, Y.J.

1991-01-01

Organometallic precursors from naphthenic acid and metal nitrates were used for the synthesis of YBCO oxide superconducting compounds. The characteristics of metal naphthenates as organometallic precursors were investigated by IR spectra, viscosity measurements, and infiltration. 123 superconducting compound obtained from 123 naphthenate showed a Tc of 90 degree K and a rather dense and elongated microstructure. Also, the melting behavior of Ba-cuprates which were used for 123 making was studied. A low-temperature melting process was developed to fabricate silver-sheathed superconducting wire with the powder-in-tube method; flowing argon gas is introduced to the system at 930-945 degree C to reduce the melting temperature of the 123 compound without silver sheath melting. It resulted in a 90 degree K Tc superconducting core with dense and locally aligned microstructure. SEM-EDS and XRD analysis, 4-probe resistance and Jc measurements, and carbon-content determinations were carried out to characterize the microstructure, grain alignment, and superconducting properties of the samples

Amino acids and glycine ethyl ester as new crystallization reagents for lysozyme

International Nuclear Information System (INIS)

Ito, Len; Shiraki, Kentaro; Yamaguchi, Hiroshi

2010-01-01

During the past two decades, amino acids and amino-acid derivatives have been applied in various fields of protein chemistry. The potential use of amino acids and their derivatives as new precipitating agents is described. Several amino acids and their derivatives are prominent additives in the field of protein chemistry. This study reports the use of charged amino acids and glycine ethyl ester as precipitants in protein crystallization, using hen egg-white lysozyme (HEWL) as a model. A discussion of the crystallization of HEWL using these reagents as precipitating agents is given

Chemical Characteristics of Precipitation in a Typical Urban Site of the Hinterland in Three Gorges Reservoir, China

Directory of Open Access Journals (Sweden)

Liuyi Zhang

2018-01-01

Full Text Available Major water-soluble ions were analyzed for two-year precipitation samples in Wanzhou, a typical urban site of the hinterland of Chinese Three Gorges Reservoir. The pH values of the precipitation were in the range of 4.0 to 8.3, and the volume-weighted mean (VWM value was 5.0. The concentration order of anions and cations was as follows: SO42->NO3->Cl->F- and NH4+>Ca2+>Na+>K+>Mg2+, respectively. Good correlations were found between SO42- and NH4+, SO42- and Ca2+, NO3- and NH4+, and NO3- and Ca2+, implying their co-occurrence in the precipitation, most likely as (NH42SO4, (NH4HSO4, NH4NO3, CaSO4, and Ca(NO32. The sum of all measured ions was 416.4 μeq L−1, indicating serious air pollution in Wanzhou. NH4+ and Ca2+ were the most important ions neutralizing the acidic compounds in the precipitation; their major sources included agricultural activity and crustal dust. Local anthropogenic activities, for example, coal burning and traffic related sources, contributed most of SO42- and NO3-. The equivalent concentration ratio of SO42-/NO3- was 4.5, indicating that excessive emission of sulfur was the main reason leading to the precipitation acidity in Wanzhou. However, this ratio was lower than the ratio (5.9 in 2000s in Wanzhou, indicating that the contribution of nitric acid to the acidity of precipitation was strengthening.

Expanding atmospheric acid deposition in China from the 1990s to the 2010s

Science.gov (United States)

Yu, Haili; Wang, Qiufeng

2017-04-01

Atmospheric acid deposition is considered a global environmental issue. China has been experiencing serious acid deposition, which is anticipated to be more serious with the country's economic development and increasing consumption of fossil fuels in recent decades. By collecting nationwide data on pH and concentrations of sulfate (SO42-) and nitrate (NO3-) in precipitation between 1980 and 2014 in China, we explored the spatiotemporal variations of precipitation acid deposition (bulk deposition) and their influencing factors. Our results showed that average precipitation pH values were 4.86 and 4.84 in the 1990s and 2010s, respectively. This suggests that precipitation acid deposition in China has not seriously changes. Average SO42- deposition declined from 30.73 to 28.61 kg S ha-1 yr-1 but average NO3- deposition increased from 4.02 to 6.79 kg N ha-1 yr-1. Specifically, the area of severe precipitation acid deposition in southern China has shrunk to some extent as a result of decreasing pollutant emissions, whereas the area of moderate precipitation acid deposition has expanded in northern China, associated with rapid industrial and transportation development. Significant positive correlations have been found between precipitation acid deposition, energy consumption, and rainfall. Our findings provide a comprehensive evaluation of the spatiotemporal dynamics of precipitation acid deposition in China over past three decades, and confirm the idea that strategies implemented to save energy and reduce pollutant emissions in China have been effective in alleviating precipitation acid deposition. These findings might be used to demonstrate how developing countries could achieve economic development and environmental protection through the implementation of advanced technologies to reduce pollutant emissions.

Effect of different MnO{sub 2} precursors on the electrochemical properties of spinel LiNi{sub 0.5}Mn{sub 1.5}O{sub 4} cathode active materials for high-voltage lithium ion batteries

Energy Technology Data Exchange (ETDEWEB)

Ma, Ye, E-mail: mayetju@tju.edu.cn [Department of Applied Chemistry, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China); Collaborative Innovation Center of Chemical Science and Engineering, Tianjin (China); Tang, Haoqing [Department of Applied Chemistry, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China); Tang, Zhiyuan, E-mail: zytang46@163.com [Department of Applied Chemistry, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China); Collaborative Innovation Center of Chemical Science and Engineering, Tianjin (China); Mao, Wenfeng [Department of Applied Chemistry, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China); Zhang, Xinhe [McNair Technology Company Limited, Dongguan, Guangdong 523700 (China)

2016-11-15

Highlights: • Synthesis of spinel LNMO via a facile template method. • The specific morphology of LNMO is closely related to that of MnO{sub 2} precursor. • LNMO using NH{sub 4}HCO{sub 3} as precipitant exhibits superior electrochemical performance. - Abstract: LiNi{sub 0.5}Mn{sub 1.5}O{sub 4} (LNMO) cathode materials with different morphologies are prepared via a facile template method using various MnO{sub 2} precursors. The structures, morphologies and electrochemical properties of the as-prepared LiNi{sub 0.5}Mn{sub 1.5}O{sub 4} samples are tested by various physical and electrochemical methods. The results of characterization show that the spinel LNMO cathode materials have good crystal structure and the MnO{sub 2} precursors have no effect on the final products. Moreover, the specific morphology of LNMO is closely related to that of MnO{sub 2} precursor, and further influence the electrochemical performance. In addition, the LNMO sample using NH{sub 4}HCO{sub 3} as precipitant exhibits excellent rate capability and cyclic stability in all as-prepared samples. Cycled at 0.5 and 1 C, the discharge capacities of LNMO cathode active particles using NH{sub 4}HCO{sub 3} as precipitant are 110.6 and 102.2 after 200 charge–discharge cycles, respectively, which are the largest compared with the LNMO using (NH{sub 4}){sub 2}S{sub 2}O{sub 8} and KMnO{sub 4} as oxidants.

Synthesis and cathodoluminescent properties of Y2SiO5:Tb3+ phosphors prepared from uniform precursor

International Nuclear Information System (INIS)

Fan Deyong; Yang Sen; Wang Jieqiong; Zheng Aqun; Song Xiaoping; Yu Demei

2012-01-01

The luminescent properties of phosphors are sensitive to the size of phosphor particles. The commercial Y 2 SiO 5 :Tb 3+ phosphors usually show relatively larger particle size (5–10 μm) due to the irregular morphology of rare earth oxide precursor and thus degrade the luminescent properties. In this paper, we report the Y 2 SiO 5 :Tb 3+ phosphors synthesized from the uniform Tb-doped Y 2 O 3 precursor by a homogeneous precipitation method. Compared with the commercial phosphors, the obtained Y 2 SiO 5 :Tb 3+ phosphors manifest the uniform morphology with much smaller particles distributing from 0.8 μm to 1.9 μm. Consequently, the cathodoluminescent intensity under low excitation voltage (1–5 kV) was increased, demonstrating a strong green emission with a dominant wavelength of 545 nm. Our results indicate an effective way to develop the high-quality phosphors for field emission display. - Highlights: ► The Y 2 SiO 5 :Tb 3+ phosphors are synthesized by a homogeneous precipitation method. ► They manifest the uniform morphology with much smaller particles than commercial one. ► The corresponding cathodoluminescent intensity of green emission is greatly enhanced. ► Our results indicate an effective way to develop the high-quality phosphors for FED.

Pollutants removal onto novel activated carbons made from lignocellulosic precursors

OpenAIRE

Valente Nabais, Joao; Laginhas, Carlos; Carrott, Manuela; Carrott, Peter; Gomes, Jose; Suhas, Suhas; Ramires, Ana; Roman, Silvia

2009-01-01

The adsorption of phenol and mercury from dilute aqueous solutions onto new activated carbons was studied. These included activated carbons produced from novel precursors, namely rapeseed, vine shoots and kenaf, and samples oxidised with nitric acid in liquid phase. The results have shown the significant potential of rapeseed, vine shoots and kenaf for the activated carbon production. The activated carbons produced by carbon dioxide activation were mainly microporous with BET apparent surface...

The elusive indigo precursors in woad (Isatis tinctoria L.)--identification of the major indigo precursor, isatan A, and a structure revision of isatan B.

Science.gov (United States)

Oberthür, Christine; Schneider, Bernd; Graf, Heidemarie; Hamburger, Matthias

2004-01-01

A metabolite-profiling study of shock-frozen leaves of Isatis tinctoria L., an old indigo dye plant and medicinal herb, revealed a complex pattern of indigo-forming compounds with higher polarities than the known indigo precursors isatan B and indican. These highly unstable compounds underwent rapid post-harvest transformation and were not detected in air-dried leaves. The major indigo precursor, named isatan A (4), was isolated by rapid normal-phase and gel chromatography, along with isatan B (3). A full spectral data set of 3 showed that the previous structure assignment as 'indoxyl-5-ketogluconate' has to be revised to 1H-indol-3-yl beta-D-ribohex-3-ulopyranoside. Isatan A (4) was identified as 1H-indol-3-yl 6'-O-(carboxyacetyl)-beta-D-ribohex-3'-ulopyranoside. In aqueous solution, glycosides 3 and 4 occur as hydrates and undergo rapid hydrolysis under very mild acidic or basic conditions.

Characterisation of Suspension Precipitated Nanocrystalline Hydroxyapatite Powders

International Nuclear Information System (INIS)

Mallik, P K; Swain, P.K.; Patnaik, S.C

2016-01-01

Hydroxyapatite (HA) is a well-known biomaterial for coating on femoral implants, filling of dental cavity and scaffold for tissue replacement. Hydroxyapatite possess limited load bearing capacity due to their brittleness. In this paper, the synthesis of nanocrystalline hydroxyapatite powders was prepared by dissolving calcium oxide in phosphoric acid, followed by addition of ammonia liquor in a beaker. The prepared solution was stirred by using magnetic stirrer operated at temperature of 80°C for an hour. This leads to the formation of hydroxyapatite precipitate. The precipitate was dried in oven for overnight at 100°C. The dried agglomerated precipitate was calcined at 800°C in conventional furnace for an hour. The influence of calcium oxide concentration and pH on the resulting precipitates was studied using BET, XRD and SEM. As result, a well-defined sub-rounded morphology of powders size of ∼41 nm was obtained with a salt concentration of 0.02 M. Finally, it can be concluded that small changes in the reaction conditions led to large changes in final size, shape and degree of aggregation of the hydroxyapatite particles. (paper)

Acid Balance, Dietary Acid Load, and Bone Effects—A Controversial Subject

Directory of Open Access Journals (Sweden)

Lynda Frassetto

2018-04-01

Full Text Available Modern Western diets, with higher contents of animal compared to fruits and vegetable products, have a greater content of acid precursors vs. base precursors, which results in a net acid load to the body. To prevent inexorable accumulation of acid in the body and progressively increasing degrees of metabolic acidosis, the body has multiple systems to buffer and titrate acid, including bone which contains large quantities of alkaline salts of calcium. Both in vitro and in vivo studies in animals and humans suggest that bone base helps neutralize part of the dietary net acid load. This raises the question of whether decades of eating a high acid diet might contribute to the loss of bone mass in osteoporosis. If this idea is true, then additional alkali ingestion in the form of net base-producing foods or alkalinizing salts could potentially prevent this acid-related loss of bone. Presently, data exists that support both the proponents as well as the opponents of this hypothesis. Recent literature reviews have tended to support either one side or the other. Assuming that the data cited by both sides is correct, we suggest a way to reconcile the discordant findings. This overview will first discuss dietary acids and bases and the idea of changes in acid balance with increasing age, then review the evidence for and against the usefulness of alkali therapy as a treatment for osteoporosis, and finally suggest a way of reconciling these two opposing points of view.

Synthesis of amorphous acid iron phosphate nanoparticles

International Nuclear Information System (INIS)

Palacios, E.; Leret, P.; Fernández, J. F.; Aza, A. H. De; Rodríguez, M. A.

2012-01-01

A simple method to precipitate nanoparticles of iron phosphate with acid character has been developed in which the control of pH allows to obtain amorphous nanoparticles. The acid aging of the precipitated amorphous nanoparticles favored the P–O bond strength that contributes to the surface reordering, the surface roughness and the increase of the phosphate acid character. The thermal behavior of the acid iron phosphate nanoparticles has been also studied and the phosphate polymerization at 400 °C produces strong compacts of amorphous nanoparticles with interconnected porosity.

A 15-year record (2001–2015 of the ratio of nitrate to non-sea-salt sulfate in precipitation over East Asia

Directory of Open Access Journals (Sweden)

S. Itahashi

2018-02-01

Full Text Available Acidifying species in precipitation can have severe impacts on ecosystems. The chemical composition of precipitation is directly related to the amount of precipitation; accordingly, it is difficult to identify long-term variation in chemical concentrations. The ratio of the nitrate (NO3− to non-sea-salt sulfate (nss-SO42− concentration in precipitation on an equivalent basis (hereinafter, Ratio is a useful index to investigate the relative contributions of these acidifying species. To identify the long-term record of acidifying species in precipitation over East Asia, the region with the highest emissions worldwide, we compiled ground-based observations of the chemical composition of precipitation over China, Korea, and Japan from 2001 to 2015 based on the Acid Deposition Monitoring Network in East Asia (EANET. The spatial coverage was limited, but additional monitoring data for Japan, southern China, and northern China around Beijing were utilized. The period of analysis was divided into three phases: Phase I (2001–2005, Phase II (2006–2010, and Phase III (2011–2015. The behaviors of NO3− and nss-SO42− concentrations and hence the Ratio in precipitation were related to these precursors. The anthropogenic NOx and SO2 emissions and the NOx ∕ SO2 emission ratio were analyzed. Further, satellite observations of the NO2 and SO2 column density to capture the variation in emissions were applied. We found that the long-term trend in the NO3− concentration in precipitation was not related to the variation in NOx emission and the NO2 column. In comparison, the nss-SO42− concentration in precipitation over China, Korea, and Japan was partially connected to the changes in SO2 emissions from China, but the trends were not significant. The long-term trends of Ratio over China, Korea, and Japan were nearly flat during Phase I, increased significantly during Phase II, and were essentially flat again during Phase III. This

Study of hafnium (IV) oxide nanoparticles synthesized by polymerized complex and polymer precursor derived sol-gel methods

KAUST Repository

Ramos-Gonzá lez, R.; Garcí a-Cerda, L. A.; Alshareef, Husam N.; Gnade, Bruce E.; Quevedo-Ló pez, Manuel Angel Quevedo

2010-01-01

This work reports the preparation and characterization of hafnium (IV) oxide (HfO2) nanoparticles grown by derived sol-gel routes that involves the formation of an organic polymeric network. A comparison between polymerized complex (PC) and polymer precursor (PP) methods is presented. For the PC method, citric acid (CA) and ethylene glycol (EG) are used as the chelating and polymerizable reagents, respectively. In the case of PP method, poly(acrylic acid) (PAA) is used as the chelating reagent. In both cases, different precursor gels were prepared and the hafnium (IV) chloride (HfCl4) molar ratio was varied from 0.1 to 1.0 for the PC method and from 0.05 to 0.5 for the PP method. In order to obtain the nanoparticles, the precursors were heat treated at 500 and 800 °C. The thermal characterization of the precursor gels was carried out by thermogravimetric analysis (TGA) and the structural and morphological characterization by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The XRD patterns of the samples obtained by both methods shows the formation of HfO2 at 500 °C with monoclinic crystalline phase. The PC method exhibited also the cubic phase. Finally, the HfO2 nanoparticles size (4 to 11 nm) was determined by TEM and XRD patterns. © (2010) Trans Tech Publications.

Study of hafnium (IV) oxide nanoparticles synthesized by polymerized complex and polymer precursor derived sol-gel methods

KAUST Repository

Ramos-González, R.

2010-03-01

This work reports the preparation and characterization of hafnium (IV) oxide (HfO2) nanoparticles grown by derived sol-gel routes that involves the formation of an organic polymeric network. A comparison between polymerized complex (PC) and polymer precursor (PP) methods is presented. For the PC method, citric acid (CA) and ethylene glycol (EG) are used as the chelating and polymerizable reagents, respectively. In the case of PP method, poly(acrylic acid) (PAA) is used as the chelating reagent. In both cases, different precursor gels were prepared and the hafnium (IV) chloride (HfCl4) molar ratio was varied from 0.1 to 1.0 for the PC method and from 0.05 to 0.5 for the PP method. In order to obtain the nanoparticles, the precursors were heat treated at 500 and 800 °C. The thermal characterization of the precursor gels was carried out by thermogravimetric analysis (TGA) and the structural and morphological characterization by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The XRD patterns of the samples obtained by both methods shows the formation of HfO2 at 500 °C with monoclinic crystalline phase. The PC method exhibited also the cubic phase. Finally, the HfO2 nanoparticles size (4 to 11 nm) was determined by TEM and XRD patterns. © (2010) Trans Tech Publications.

Two pheromone precursor genes are transcriptionally expressed in the homothallic ascomycete Sordaria macrospora.

Science.gov (United States)

Pöggeler, S

2000-06-01

In order to analyze the involvement of pheromones in cell recognition and mating in a homothallic fungus, two putative pheromone precursor genes, named ppg1 and ppg2, were isolated from a genomic library of Sordaria macrospora. The ppg1 gene is predicted to encode a precursor pheromone that is processed by a Kex2-like protease to yield a pheromone that is structurally similar to the alpha-factor of the yeast Saccharomyces cerevisiae. The ppg2 gene encodes a 24-amino-acid polypeptide that contains a putative farnesylated and carboxy methylated C-terminal cysteine residue. The sequences of the predicted pheromones display strong structural similarity to those encoded by putative pheromones of heterothallic filamentous ascomycetes. Both genes are expressed during the life cycle of S. macrospora. This is the first description of pheromone precursor genes encoded by a homothallic fungus. Southern-hybridization experiments indicated that ppg1 and ppg2 homologues are also present in other homothallic ascomycetes.

Influence of starting precursors and synthesis methods on the physiochemical properties of zirconia

Energy Technology Data Exchange (ETDEWEB)

Gaydhankar, T.R., E-mail: tr.gaydhankar@ncl.res.in [Catalysis Division, National Chemical Laboratory, Pune 411008 (India); Jha, R.K. [Catalysis Division, National Chemical Laboratory, Pune 411008 (India); Nikalje, M.D. [Department of Chemistry, University of Pune, Pune 411 007 (India); Waghmare, K.J. [Catalysis Division, National Chemical Laboratory, Pune 411008 (India)

2014-07-01

Graphical abstract: Crystallite size of tetragonal phase of the zirconia samples prepared using different synthesis parameters and precursors as a function of calcination temperature. Surface area values of the zirconia samples calcined at 500 and 700 °C are in given brackets. - Highlights: • Zirconia prepared with modified sol–gel method is less stable compared with zirconia prepared by precipitation method. • Optimized synthesis conditions shifted the glow exotherm to higher temperature range indicating better thermal stability. • Tetragonal-zirconia could be synthesized in cost-effective manner using zirconium oxy-nitrate. • In our studies no co-relation between the surface area and crystallite size was observed. - Abstract: Under identical and judiciously pre-optimized synthesis conditions, the influence of different combinations of zirconium sources and/or post treatment conditions on structural properties, thermal stability, phase composition and morphology of zirconia has been investigated. High surface area tetragonal zirconia could be synthesized in a cost-effective manner from 1 M solution of zirconium oxy-nitrate at pH 11 using aqueous ammonia solution as a precipitant when calcined at 400 °C for 3 h. Irrespective of the preparation method, pH and starting precursor, zirconia samples prepared without digestion contained dominant monoclinic phase with some traces of tetragonal phase when calcined at 700 °C. Even though there is linear decrease in surface area with increase in the crystallite size for each sample as a function of calcination temperature, no co-relation between the surface area and crystallite size could be achieved. SEM images show agglomerated and irregular shape particles between 10 to 20 μm.

Processing, structure and magnetic properties correlation in co-precipitated Ca-ferrite

Energy Technology Data Exchange (ETDEWEB)

Abasht, Behzad, E-mail: abasht@gmail.com [Space Thruster Research Institute, Iranian Space Research Center, Tabriz (Iran, Islamic Republic of); Department of Metallurgy and Materials Engineering, Iran University of Science and Technology, Tehran (Iran, Islamic Republic of); Beitollahi, Ali; Mirkazemi, Seyyed Mohammad [Department of Metallurgy and Materials Engineering, Iran University of Science and Technology, Tehran (Iran, Islamic Republic of)

2016-12-15

La-substituted hexagonal calcium ferrite, Ca{sub 1−X}La{sub X}Fe{sub 12}O{sub 19} (x varies from 0 to 0.6 with the step of 0.2), was synthesized by applying co-precipitation method, in which the molar ratio of Fe{sup 3+}/(Ca{sup 2+}+La{sup 2+}) was 11. The ferrite precursors were prepared from aqueous solution of calcium nitrate, ferric nitrate and lanthanum nitrate by co-precipitation of calcium, iron and lanthanum ions by using an aqueous base of sodium hydroxide (1.5 M) at the pH of 14 and at room temperature. These precursors were calcinated with different amount of La at different temperature of 700, 1100 and 1200 °C for constant calcination time of 1 h in a static air atmosphere. Some tests such as simultaneous thermal analysis (STA), X-ray diffraction (XRD), scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM) were carried out to investigate the thermal behavior, crystallographic properties, morphology and magnetic properties of the precursor powders which were calcinated at different temperatures. The powder XRD patterns of samples which consisted of La as dopant and were calcinated at 1200 °C for 1 h, indicates the formation of calcium hexaferrite and also α-Fe{sub 2}O{sub 3} besides Magnetoplumbite-phase (M-phase). However, the results showed that CaFe{sub 4}O{sub 7} and α-Fe{sub 2}O{sub 3} phases were formed in the sample with the same condition but without using any dopant. The results of SEM showed that the calcium hexaferrite particle were regular hexagonal platelets with the size range of 1–2 µm. The magnetic properties such as maximum magnetization (M{sub Max}), remanent magnetization (M{sub r}) and coercivity (H{sub c}) were measured from the hysteresis loops. Low values of coercive field (16.3 kA m{sup −1}) and maximum magnetization (50.6 A m{sup 2} kg{sup −1}) were obtained from calcium hexaferrite particle in optimum amount of La (X=0.4) which calcinated at the temperature of 1200 °C. - Highlights: • In this

Sulfur and Hydrogen Isotope Anomalies in Meteorite Sulfonic Acids

Science.gov (United States)

Cooper, George W.; Thiemens, Mark H.; Jackson, Teresa L.; Chang, Sherwood

1997-01-01

Intramolecular carbon, hydrogen, and sulfur isotope ratios were measured on a homologous series of organic sulfonic acids discovered in the Murchison meteorite. Mass-independent sulfur isotope fractionations were observed along with high deuterium/hydrogen ratios. The deuterium enrichments indicate formation of the hydrocarbon portion of these compounds in a low-temperature environment that is consistent with that of interstellar clouds. Sulfur-33 enrichments observed in methanesulfonic acid could have resulted from gas-phase ultraviolet irradiation of a precursor, carbon disulfide. The source of the sulfonic acid precursors may have been the reactive interstellar molecule carbon monosulfide.

The essential nature of linoleic acid in mammals

DEFF Research Database (Denmark)

Hansen, Harald S.

1986-01-01

Linoleic acid [CH(CH)(CH = CHCH)(CH) COOH] is a precursor of the icosanoids -20-carbon fatty acids which include leukotrienes, prostaglandins, thromboxanes and related compounds. Until recently, the classical symptoms resulting from deficiency of linoleic and other essential fatty acids (EFAs) ha...

End point control of an actinide precipitation reactor

International Nuclear Information System (INIS)

Muske, K.R.

1997-01-01

The actinide precipitation reactors in the nuclear materials processing facility at Los Alamos National Laboratory are used to remove actinides and other heavy metals from the effluent streams generated during the purification of plutonium. These effluent streams consist of hydrochloric acid solutions, ranging from one to five molar in concentration, in which actinides and other metals are dissolved. The actinides present are plutonium and americium. Typical actinide loadings range from one to five grams per liter. The most prevalent heavy metals are iron, chromium, and nickel that are due to stainless steel. Removal of these metals from solution is accomplished by hydroxide precipitation during the neutralization of the effluent. An end point control algorithm for the semi-batch actinide precipitation reactors at Los Alamos National Laboratory is described. The algorithm is based on an equilibrium solubility model of the chemical species in solution. This model is used to predict the amount of base hydroxide necessary to reach the end point of the actinide precipitation reaction. The model parameters are updated by on-line pH measurements

Generation of dose-response relationships to assess the effects of acidity in precipitation on growth and productivity of vegetation

International Nuclear Information System (INIS)

Evans, L.S.

1981-01-01

Experiments were performed with several plant species in natural environments as well in a greenhouse and/or tissue culture facilities to establish dose-response functions of plant responses to simulated acidic rain in order to determine environmental risk assessments to ambient levels of acidic rain. Response functions of foliar injury, biomass of leaves and seed of soybean and pinto beans, root yields of radishes and garden beets, and reproduction of bracken fern are considered. The dose-response function of soybean seed yields with the hydrogen ion concentration of simulated acidic rainfalls was expressed by the equation y = 21.06-1.01 log x where y = seed yield in grams per plant and x = the hydrogen concentration if μeq l -1 . The correlation coefficient of this relationship was -0.90. A similar dose-response function was generated for percent fertilization of ferns in a forest understory. When percent fertilization is plotted on logarithmic scale with hydrogen ion concentration of the simulated rain solution, the Y intercept is 51.18, slope -0.041 with a correlation coefficient of -0.98. Other dose-response functions were generated that assist in a general knowledge as to which plant species and which physiological processes are most impacted by acidic precipitation. Some responses did not produce convenient dose-response relationships. In such cases the responses may be altered by other environmental factors or there may be no differences among treatment means

Production of the Lax Ca1-x Cry Al1-y O3 compound through hydroxide precipitation

International Nuclear Information System (INIS)

Martins, L.C.; Machado, A.J.S.

1996-01-01

Purposing to reduce the cost of preparation of the lanthanum chromite doped with calcium and aluminum, it was made a study of the condition of hydroxide precipitation, using calcium, chromium and aluminum nitrates and lanthanum oxide, as precursors and as precipitate agent was used potassium hydroxide. In this study are showed results about the reaction kinetic, x-ray diffraction and yield as function of the pH. These results suggest a high yield for also elements studied. The phase of stoichiometry, La 0.8 Ca 0.2 Cr 0.75 Al 0.25 O 3 was obtained in low temperature. In fact, this process is viable to produce of lanthanum chromite doped with calcium and aluminum. (author)

Colloidal infrared reflective and transparent conductive aluminum-doped zinc oxide nanocrystals

Science.gov (United States)

Buonsanti, Raffaella; Milliron, Delia J

2015-02-24

The present invention provides a method of preparing aluminum-doped zinc oxide (AZO) nanocrystals. In an exemplary embodiment, the method includes (1) injecting a precursor mixture of a zinc precursor, an aluminum precursor, an amine, and a fatty acid in a solution of a vicinal diol in a non-coordinating solvent, thereby resulting in a reaction mixture, (2) precipitating the nanocrystals from the reaction mixture, thereby resulting in a final precipitate, and (3) dissolving the final precipitate in an apolar solvent. The present invention also provides a dispersion. In an exemplary embodiment, the dispersion includes (1) nanocrystals that are well separated from each other, where the nanocrystals are coated with surfactants and (2) an apolar solvent where the nanocrystals are suspended in the apolar solvent. The present invention also provides a film. In an exemplary embodiment, the film includes (1) a substrate and (2) nanocrystals that are evenly distributed on the substrate.

Distribution of 32P-phosphate in guinea pig central nervous system after intraventricular administration of precursor

International Nuclear Information System (INIS)

Bukovsky, V.; Hage Ali, M.A.; Mezes, V.

1982-01-01

Within 20 minutes after administration into the right lateral ventricle, precursor balance is achieved in both cerebral hemispheres, the brain stem and the cerebellum. A different course was observed in the medulla oblongata and the spinal cord. Twenty minutes following administration of the precursor, the amount of radioactivity decreased in the following order of sequence: the right hemisphere, the brain stem, the cerebellum, the left hemisphere, the medulla oblongata, and the spinal cord. Of the total amount of phosphates in the acid-soluble fraction of the whole brain and cerebellum, inorganic phosphates constxtute 50%, and there are no differences between the two parts. 60 minutes after administration of the labelled phosphate, the specific activity of total phosphates in the acid-soluble fraction of the brain and cerebellum is higher than the specific activity of inorganic phosphates. (author)

In vitro precipitation of electrodeposited calcium-deficient hydroxyapatite coatings on Ti6Al4V substrate

International Nuclear Information System (INIS)

Dumelie, N.; Benhayoune, H.; Richard, D.; Laurent-Maquin, D.; Balossier, G.

2008-01-01

In this study, electrodeposited calcium phosphate coatings were characterized by X-ray diffraction, using a scanning electron microscope equipped with an EDAX detector, before and after immersion in DMEM (Dulbecco's Modified Eagle Medium). After 1, 7, 14, and 21 days of immersion, the calcium and phosphate contents in solution were measured by inductively coupled plasma atomic emission spectrometry (ICP-AES). The results indicated that precipitation of the coating occurred. Before immersion in DMEM, the electrodeposited coating was a mixed crystalline and amorphous calcium-deficient hydroxyapatite with a Ca/P atomic ratio of about 1.5, but during the immersion period these phases rapidly disappeared and were followed by the precipitation of a crystalline apatite with a Ca/P atomic ratio near 1.65. On the basis of these results, we conclude that an electrodeposited calcium phosphate coating on roughened titanium alloy substrate may act as a precursor for newly precipitated calcium phosphate in in vitro experiments independent of cellular activities

Catalyseurs monométalliques ou bimétalliques à base de Ru et Au pour l'oxydation de composés organiques dans l'eau

OpenAIRE

Tran , Ngoc Dung

2008-01-01

TiO2, CeO2, ZrO2 and CexZr(1-x)O2 supported gold catalysts have been prepared via deposition-precipitation, using different precipitation agents. The influence of the main preparation parameters on the formation of gold nanoparticles (initial concentration in precursor, pH, washing and drying modes, pretreatment...) has been studied. These catalysts are active in the catalytic wet air oxidation (CWAO) of model compounds, such as succinic acid, acetic acid and phenol. Metallic gold (Au0) is th...

Green Polymer Precursors from Biomass-Based Levulinic Acid

NARCIS (Netherlands)

Chalid, M.; Heeres, H.J.; Broekhuis, A.A.

2012-01-01

Levulinic acid (LA) has been identified as a suitable chemical feedstock that can be isolated from biomass. Its conversion into γ-valerolactone (GVL) via hydrogenation and ringclosure to the lactone has been studied as a versatile route to the manufacture of biodegradable polyesters. For

Preparation of silica nanoparticles through microwave-assisted acid-catalysis.

Science.gov (United States)

Lovingood, Derek D; Owens, Jeffrey R; Seeber, Michael; Kornev, Konstantin G; Luzinov, Igor

2013-12-16

Microwave-assisted synthetic techniques were used to quickly and reproducibly produce silica nanoparticle sols using an acid catalyst with nanoparticle diameters ranging from 30-250 nm by varying the reaction conditions. Through the selection of a microwave compatible solvent, silicic acid precursor, catalyst, and microwave irradiation time, these microwave-assisted methods were capable of overcoming the previously reported shortcomings associated with synthesis of silica nanoparticles using microwave reactors. The siloxane precursor was hydrolyzed using the acid catalyst, HCl. Acetone, a low-tan δ solvent, mediates the condensation reactions and has minimal interaction with the electromagnetic field. Condensation reactions begin when the silicic acid precursor couples with the microwave radiation, leading to silica nanoparticle sol formation. The silica nanoparticles were characterized by dynamic light scattering data and scanning electron microscopy, which show the materials' morphology and size to be dependent on the reaction conditions. Microwave-assisted reactions produce silica nanoparticles with roughened textured surfaces that are atypical for silica sols produced by Stöber's methods, which have smooth surfaces.

Effect of temperature on the reaction pathway of calcium carbonate formation via precursor phases

Science.gov (United States)

Purgstaller, Bettina; Mavromatis, Vasileios; Konrad, Florian; Dietzel, Martin

2016-04-01

It has been earlier postulated that some biogenic and sedimentary calcium carbonate (CaCO3) minerals (e.g. calcite and aragonite) are secondary in origin and have originally formed via a metastable calcium carbonate precursor phase (e.g. amorphous CaCO3, [1-2]). Such formation pathways are likely affected by various physicochemical parameters including aqueous Mg and temperature. In an effort to improve our understanding on the formation mechanism of CaCO3 minerals, precipitation experiments were carried out by the addition of a 0.6 M (Ca,Mg)Cl2 solution at distinct Mg/Ca ratios (1/4 and 1/8) into a 1 M NaHCO3 solution under constant pH conditions(8.3 ±0.1). The formation of CaCO3 was systematically examined as a function of temperature (6, 12, 18 and 25 ±0.3° C). During the experimental runs mineral precipitation was monitored by in situ Raman spectroscopy as well as by continuous sampling and analyzing of precipitates and reactive solutions. The results revealed two pathways of CaCO3 formation depending on the initial Mg/Ca ratio and temperature: (i) In experiments with a Mg/Ca ratio of 1/4 at ≤ 12° C as well as in experiments with a Mg/Ca ratio of 1/8 at ≤ 18° C, ikaite (CaCO3 6H2O) acts as a precursor phase for aragonite formation. (ii) In contrast higher temperatures induced the formation of Mg-rich amorphous CaCO3 (Mg-ACC) which was subsequently transformed to Mg-rich calcite. In situ Raman spectra showed that the transformation of Mg-ACC to Mg-calcite occurs at a higher rate (˜ 8 min) compared to that of ikaite to aragonite (> 2 h). Thus, the formation of aragonite rather than of Mg-calcite occurs due to the slower release of Ca2+and CO32- ions into the Mg-rich reactive solution during retarded ikaite dissolution. This behavior is generally consistent with the observation that calcite precipitation is inhibited at elevated aqueous Mg/Ca ratios. [1] Addadi L., Raz S. and Weiner S. (2003) Advanced Materials 15, 959-970. [2] Rodriguez-Blanco J. D