Search results for "Nitrate"

Toward a Quality Guide to Facilitate the Transference of Analytical Methods from Research to Testing Laboratories: A Case Study

2009

Abstract At present, there is no single viewpoint that defines QA strategies in analytical chemistry. On the other hand, there are no unique protocols defining a set of analytical tasks and decision criteria to be performed during the method development phase (e.g., by a single research laboratory) in order to facilitate the transference to the testing laboratories intending to adapt, validate, and routinely use this method. This study proposes general criteria, a priori valid for any developed method, recommended as a provisional quality guide containing the minimum internal tasks necessary to publish new analytical method results. As an application, the selection of some basic internal qu…

Structure and activity of the nitrate-reducing community in the rhizosphere of Lolium perenne and Trifolium repens under long-term elevated atmospher…

2004

Rhizosphere soil was sampled in monocultures of Lolium perenne and Trifolium repens in June and October 2002, at two different nitrogen fertilisation levels (14 and 56 g N m−2 year−1) and under two pCO2 atmospheres (360 and 600 ppmv) at the Swiss FACE (Free Air Carbon dioxide Enrichment) site. Directly extracted soil DNA was analysed with restriction fragment length polymorphism (PCR-RFLP) by use of degenerated primers for the narG gene encoding the active site of the membrane-bound nitrate reductase. The corresponding enzyme activity of the nitrate reductase was determined colorimetrically after 24 h of anaerobic incubation. The narG PCR-RFLP fingerprints showed that the structure of the n…

Nitrate/oxygen co-sensing by an NreA/NreB sensor complex ofStaphylococcus carnosus

2013

In Staphylococci maximal induction of nitrate reductase (narGHJI genes) requires anaerobic conditions, the presence of nitrate, and the NreABC regulatory system. Aerobic regulation is effected by the NreB/NreC two-component system. The role of the nitrate receptor NreA in nitrate induction and its relation to aerobic regulation was analysed in Staphylococcus carnosus. Nitrate induction of a narG-lip reporter gene required presence of NreB/NreC. When nreA was deleted, nitrate was no longer required for maximal induction, suggesting that NreA is a nitrate regulated inhibitor of NreB/NreC. In vitro, NreA and mutant NreA(Y95A) decreased NreB phosphorylation in part or completely, which was due …

Household water source and the risk of childhood brain tumours: results of the SEARCH International Brain Tumor Study.

2004

Background The period in utero is a time of increased vulnerability. Offspring of pregnant women exposed to carcinogenic substances in drinking water may be more likely to develop cancer. We examined whether household water source and the presence of nitrates or nitrites in residential water were associated with increased risks of childhood brain tumours (CBT). Methods We used data from a multicentre, case-control study with maternal information on residential water source, and nitrate/nitrite levels of tap water measured by dipstick. Subjects included 836 CBT cases and 1485 controls from five countries. Results The risks of CBT associated with reliance on well water (versus public water) d…

Sulfur cycling and methanogenesis primarily drive microbial colonization of the highly sulfidic Urania deep hypersaline basin

2009

Urania basin in the deep Mediterranean Sea houses a lake that is >100 m deep, devoid of oxygen, 6 times more saline than seawater, and has very high levels of methane and particularly sulfide (up to 16 mM), making it among the most sulfidic water bodies on Earth. Along the depth profile there are 2 chemoclines, a steep one with the overlying oxic seawater, and another between anoxic brines of different density, where gradients of salinity, electron donors and acceptors occur. To identify and differentiate the microbes and processes contributing to the turnover of organic matter and sulfide along the water column, these chemoclines were sampled at a high resolution. Bacterial cell numbers…

Exploring Solvent-free Citrate-Nitrate Auto-Combustion for the Synthesis of SOFC Electrocatalysts

2009

Copper nanowires as higly sensitivite electrode for nitrate ions in water

Agricultural and livestock sectors are the main sources of nitrate ions contamination in water and foodstuff. [1]. High nitrate concentration is dangerous for both environment (algae overgrowth) and human health. Nitrate ions can be converted in different harmful nitrogen based compound such as NO2-, NO, N-nitroso compounds [2] that are responsible of several diseases such as cancer, Parkinson [3-4]. For these reasons, the Environmental Protection Agency, has established the maximum amount of nitrate ions in drinkable water at 44 mg/l, limit that is valid in many European countries [5]. Generally, spectroscopy techniques are the most used because allow to carry out analyses with high precis…

Involvement of nitrate reductase and pyoverdine in competitiveness of Pseudomonas fluorescens strain C7R12 in soil

2001

ABSTRACT Involvement of nitrate reductase and pyoverdine in the competitiveness of the biocontrol strain Pseudomonas fluorescens C7R12 was determined, under gnotobiotic conditions, in two soil compartments (bulk and rhizosphere soil), with the soil being kept at two different values of matric potential (−1 and −10 kPa). Three mutants affected in the synthesis of either the nitrate reductase (Nar − ), the pyoverdine (Pvd − ), or both (Nar − Pvd − ) were used. The Nar − and Nar − Pvd − mutants were obtained by site-directed mutagenesis of the wild-type strain and of the Pvd − mutant, respectively. The selective advantage given by nitrate reductase and pyoverdine to the wild-type strain was as…

Silver ion oxidative coupling of diene and triene-diolates of unsaturated carboxylic acids. A facile synthesis of octa- and dodeca-dienedioic acids

1988

Abstract Polyunsaterated dicarboxylic acids 3 and 5 are very easily prepared by oxidative coupling of lithium diene- and triene-diolates 1 and 2 with silver nitrate.

Green synthesis of silver nanoparticles mediated by Pulicaria glutinosa extract

2013

Mujeeb Khan,1 Merajuddin Khan,1 Syed Farooq Adil,1 Muhammad Nawaz Tahir,2 Wolfgang Tremel,2 Hamad Z Alkhathlan,1 Abdulrahman Al-Warthan,1 Mohammed Rafiq H Siddiqui1 1Department of Chemistry, College of Science, King Saud University, Riyadh, Kingdom of Saudi Arabia; 2Institute of Inorganic and Analytical Chemistry, Johannes Gutenberg-University of Mainz, Mainz, Germany Abstract: The green synthesis of metallic nanoparticles (NPs) has attracted tremendous attention in recent years because these protocols are low cost and more environmentally friendly than standard methods of synthesis. In this article, we report a simple and eco-friendly method for the synthesis of silver NPs using an aqueous…