Showing papers on "Urea published in 2017"

High salt intake reprioritizes osmolyte and energy metabolism for body fluid conservation

Abstract: Natriuretic regulation of extracellular fluid volume homeostasis includes suppression of the renin-angiotensin-aldosterone system, pressure natriuresis, and reduced renal nerve activity, actions that concomitantly increase urinary Na+ excretion and lead to increased urine volume. The resulting natriuresis-driven diuretic water loss is assumed to control the extracellular volume. Here, we have demonstrated that urine concentration, and therefore regulation of water conservation, is an important control system for urine formation and extracellular volume homeostasis in mice and humans across various levels of salt intake. We observed that the renal concentration mechanism couples natriuresis with correspondent renal water reabsorption, limits natriuretic osmotic diuresis, and results in concurrent extracellular volume conservation and concentration of salt excreted into urine. This water-conserving mechanism of dietary salt excretion relies on urea transporter-driven urea recycling by the kidneys and on urea production by liver and skeletal muscle. The energy-intense nature of hepatic and extrahepatic urea osmolyte production for renal water conservation requires reprioritization of energy and substrate metabolism in liver and skeletal muscle, resulting in hepatic ketogenesis and glucocorticoid-driven muscle catabolism, which are prevented by increasing food intake. This natriuretic-ureotelic, water-conserving principle relies on metabolism-driven extracellular volume control and is regulated by concerted liver, muscle, and renal actions.

Role of Slow-Release Nanocomposite Fertilizers on Nitrogen and Phosphate Availability in Soil

Abstract: Developing efficient crop fertilization practices has become more and more important due to the ever-increasing global demand for food production. One approach to improving the efficiency of phosphate and urea fertilization is to improve their interaction through nanocomposites that are able to control the release of urea and P in the soil. Nanocomposites were produced from urea (Ur) or extruded thermoplastic starch/urea (TPSUr) blends as a matrix in which hydroxyapatite particles (Hap) were dispersed at ratios 50% and 20% Hap. Release tests and two incubation experiments were conducted in order to evaluate the role played by nanocomposites in controlling the availability of nitrogen and phosphate in the soil. Tests revealed an interaction between the fertilizer components and the morphological changes in the nanocomposites. TPSUr nanocomposites provided a controlled release of urea and increased the release of phosphorus from Hap in citric acid solution. The TPSUr nanocomposites also had lower NH3 volatilization compared to a control. The interaction resulting from dispersion of Hap within a urea matrix reduced the phosphorus adsorption and provided higher sustained P availability after 4 weeks of incubation in the soil.

Highly active Ni-Fe double hydroxides as anode catalysts for electrooxidation of urea

Abstract: Urea is a safe and sustainable chemical for electrochemical energy conversion and storage. However, the sluggish kinetic rates of the electrooxidation reaction of urea as well as catalyst stability still remain to be challenges. In this work, we investigated several catalysts for the electro-oxidation of urea by directly growing NiM double hydroxides (M = Cr, Mn, Fe, Co, Cu, Zn) on carbon fibre cloth and nickel foam electrodes through a facile one-step hydrothermal synthesis method. The results indicated that the activity was significantly related to the elemental composition. Among the investigated double hydroxides, the NiFe double hydroxide (DH) catalyst showed the highest activity, which achieved a specific current density of ∼95 mA cm−2 mg−1 at 0.5 V vs. Ag/AgCl, about 10 times larger than that of Ni(OH)2. In addition, the NiFe DH also had a high activity when grown on a Ni foam substrate. This NiFe DH performs well in the aspect of urea oxidation stability, demonstrating it to be a promising low-cost and stable catalyst for the efficient electrooxidation of urea under alkaline conditions.

Electroactivity of NiCr Catalysts for Urea Oxidation in Alkaline Electrolyte

Abstract: Inexpensive Ni-based catalysts have shown comparable urea oxidation activity to that of precious metals in an alkaline electrolyte. We investigated the urea oxidation on binary NiCr catalysts supported on a carbon matrix in 1 m KOH and 0.33 m urea. The amount of Cr was optimized in the catalyst layer, and it was found that the catalyst with 40 % Cr (Ni60Cr40/C) exhibits the highest urea oxidation activity of 2933 mA mgNi−1 at 0.55 V; with an onset potential of 0.32 V vs. Ag/AgCl. Chronoamperometry curves of NiCr catalysts show stability over 2000 s in oxidizing urea. A lower charge-transfer resistance of 3.3 Ω cm2 at 0.40 V was calculated on Ni60Cr40/C compared to that on Ni/C (13 Ω cm2). The exceptionally high mass activity of Ni60Cr40/C is attributed to its improved charge-transfer kinetics, enhanced surface coverage of NiII/NiIII redox center, better dispersion of Ni nuclei, and a low-Tafel slope.

Design and development of electrochemical biosensor for the simultaneous detection of melamine and urea in adulterated milk samples

Abstract: The consumption of melamine and urea contaminated cow milk causes indigestion, acidity, ulcers and kidney stones in humans. In this context, a highly sensitive acetylcholinesterase cyclic voltammetric biosensor based on zinc oxide nanospheres modified Pt electrode has been successfully developed for the simultaneous determination of melamine and urea in cow milk sample. The fabricated bioelectrode showed 100% permeability to the binary mixture of melamine and urea, which in-turn enhanced selectivity. In addition, linear regression models for the estimation of binary mixture of melamine and urea in cow milk were formulated by keeping added melamine and urea as dependent variables and the estimated electrochemical paremeters as independent variables. The prediction performance of linear regression models was validated using %recovery, relative prediction error and root mean square error for cross-validation. The developed Pt/ZnO/AChE/Chitosan bioelectrode detected melamine and urea over a range of 1–20 nM with a limit of detection of 3 pM and 1 pM respectively. The proposed sensor exhibited good recovery (99.96–102.22%), thus providing a promising tool for analysis of melamine and urea in cow milk samples.

Calcium Chelation of Lignin from Pulping Spent Liquor for Water-Resistant Slow-Release Urea Fertilizer Systems

Abstract: Slow-release fertilizers represent a possible large-scale application for plant polymers Here we show a facile way to stabilize urea in fertilizer systems by lignin Chelation of kraft black liquor with calcium acetate at pH 13 precipitated lignin as a calcium complex (Ca-lignin), which offered beneficial effects if compared to those from lignin obtained by precipitation at low pH (Acid-lignin) The reduced affinity of water to Ca-lignin was exploited in the formulation of slow-release fertilizers comprising wheat straw sections impregnated with Ca-lignin in molten urea Compared to the case of Acid-lignin, immersion in water was slowed down more extensively by Ca-lignin After 24 h incubation at low moisture conditions, the highest proportion of urea retained in the Ca-lignin/straw fertilizer system was 58% The water resistance of Ca-lignin was explained by a lower aqueous solubility that differed from the typical pH-dependent solubility of Acid-lignin Electron microscopy, infrared spectroscopy, and a

Reducing nitrogen losses through ammonia volatilization and surface runoff to improve apparent nitrogen recovery of double cropping of late rice using controlled release urea.

Abstract: Controlled release fertilizer can reduce nitrogen losses to the environment while increasing grain yield and improving apparent nitrogen recovery (ANR) of rice. However, few studies have evaluated the comparative efficacy of different polymer-coated urea products on nitrogen (N) losses, ANR, and N uptake of rice. A 2-year field experiment was conducted to compare the effects of three different types of polymer-coated urea fertilizer on nitrogen losses through NH3 volatilization and surface runoff to the environment, ANR, grain yield, and N uptake as compared to conventional urea of rice. Six treatments including (1) control with 0 kg N ha−1 (CK), (2) basal application of urea (Ub), (3) split application (Us) of urea (50% at transplanting, 25% at tillering, and 25% at panicle stages), (4) CRU-1 (polyurethane-coated urea), (5) CRU-2 (degradable polymer-coated urea), and (6) CRU-3 (water-based polymer-coated urea) all applied at 165 kg N ha−1. It was found that CRU-2 resulted in the highest grain yield and panicle numbers among the N fertilization treatments in 2013 and 2014. Applying CRU could help increase N uptake in rice, reduce N losses through NH3 volatilization and surface runoff, and hence improve ANR. Its single dose can meet the nutrient demand of the rice plant. Controlled release urea could be adopted as an effective mitigation alternative to retard N losses through NH3 volatilization and surface runoff while improving ANR of double cropping of late rice.

Interactive effects of urea and lipid content confound stable isotope analysis in elasmobranch fishes

Abstract: Stable isotope analysis (SIA) is becoming a commonly used tool to study the ecology of elasmobranchs. However, the retention of urea by elasmobranchs for osmoregulatory purposes may bias the analysis and interpretation of SIA data. We examined the effects of removing urea and lipid on the stable isotope composition of 14 species of sharks, skates, and rays from the eastern North Pacific Ocean. While effects were variable across taxa, removal of urea generally increased δ15N and C:N. Urea removal had less influence on δ13C, whereas extracting urea and lipid generally increased δ15N, C:N, and δ13C. Because C:N values of nonextracted tissues are often used to infer lipid content and adjust δ13C, shifts in C:N following urea extraction will change the inferred lipid content and bias any mathematical adjustment of δ13C. These results highlight the importance of urea and lipid extraction and demonstrate the confounding effects of these compounds, making it impossible to use C:N of non-urea-extracted samples as ...

A new urease-inhibiting formulation decreases ammonia volatilization and improves maize nitrogen utilization in North China Plain

Abstract: Overuse of urea, low nitrogen (N) utilization, and large N losses are common in maize production in North China Plain (NCP). To solve these problems, we conducted two field experiments at Shangzhuang and Quzhou in NCP to test the ability of a newly developed urease inhibitor product Limus® to decrease NH3 volatilization from urea applied to maize. Grain yield, apparent N recovery efficiency (REN) and N balance when using urea applied with or without Limus were also measured over two maize growing seasons. Cumulative NH3 loss in the two weeks following urea application without Limus ranged from 9–108 kg N ha−1, while Limus addition significantly decreased NH3 loss by a mean of 84%. Urea with Limus did not significantly increase maize yields (P < 0.05) compared with urea alone. However, a significant 11–17% improvement in REN with Limus was observed at QZ. The use of urea-N plus Limus would permit a reduction in N applications of 55–60% compared to farmers’ practice and/or further 20% N saving compared with optimized urea-N rate (150 kg N ha−1, based on N requirement by target yield of 7.5 t ha−1), and would achieve the same maize yields but with significantly decreased NH3 loss and increased N utilization.

Effect of different foliar nitrogen applications on the must amino acids and glutathione composition in Cabernet Sauvignon vineyard

Abstract: The effect of different foliar nitrogen applications on the must amino acids and glutathione composition in a Cabernet Sauvignon vineyard was studied. Nitrogen treatments applied to the grapevines were urea (Ur), urea plus sulphur (Ur + S) and arginine (Arg). Also, two commercial nitrogen complexes, Basfoliar Algae (BA) and Nutrimyr Thiols (NT), were used. For each treatment, 2 kg N/ha was applied, divided in two applications. The commercial nitrogen complexes (NT and BA) improved the amino acid content. Ur + S treatment had a better assimilation than Ur, increasing the amino acid composition. Arg treatment did not increase the content of any amino acid, however increased the easily extractable anthocyanins, total anthocyanins and total polyphenol index. Organic sources treatments (Arg, NT and BA) increased glutathione concentration. These results can be of oenological interest to improve grape quality enhancing must amino acid and glutathione content in high proline accumulator variety.

Functional porous carbon nanospheres from sustainable precursors for high performance supercapacitors

Abstract: Functional porous carbon nanospheres with tunable textural properties and nitrogen functionalities were synthesized from a cheap and sustainable phenolic carbon precursor (tannic acid) and nitrogen precursor (urea) using a facile one-step salt-templating method. The diverse functional carbons were obtained by calcination of mixtures of different molar ratios of urea to tannic acid (0 : 1, 5 : 1, 9 : 1, 13 : 1 and 17 : 1) with a eutectic salt (NaCl/ZnCl2) that was used as the porogen. The physico-chemical characterization of the obtained microporous carbons demonstrated that the textural properties, morphology, surface functionalities, and conductivity were strongly influenced by the molar ratio of urea to tannic acid. The nitrogen content in the carbons increased with the molar ratio of urea, reaching a maximum of 8.83% N at the highest molar ratio while the specific surface area (SBET) of the microporous carbons varied from 890 m2 g−1 to 1570 m2 g−1 depending on the synthesis conditions. The electrochemical performance of the carbon nanospheres in the ionic liquid 1-butyl-1-methylpyrrolidinium bis(fluorosulfonyl)imide (PYR14FSI) was also significantly influenced by the synthesis conditions due to the combined effect of textural properties, morphology, nitrogen functionalities and electrical conductivity. Supercapacitors based on the functional porous carbon synthesized with a molar ratio of urea to tannic acid of 9 : 1 exhibited the best performance, with a specific capacitance as high as 110 F g−1 and a real energy density of 33 W h kg−1, when charged–discharged at 3.5 V in PYR14FSI.

Synthesis of highly intercalated urea-clay nanocomposite via domestic montmorillonite as eco-friendly slow-release fertilizer

Abstract: The present study describes the preparation and characterization of montmorillonite-urea nanocomposites (Mt-Ur) using aqueous suspension technique at various stirring times and different ratio of montmorillonite to urea (Mt/Ur) via an impure and domestic montmorillonite (Mt), without the application of any chemical reagents and high-energy-demand process (environmentally friendly). The intercalation of urea into Mt interlayer was clearly demonstrated by a significant expansion of d001 spacing (interlayer space of Mt) from 1.23 to 1.71 nm which has not yet been reported by aqueous suspension technique. Analyses performed by Fourier transform-infrared spectroscopy (FT-IR), Thermogravimetric analysis (TGA) and X-ray diffraction (XRD) also confirmed the effectiveness of this simple process to intercalate the urea into clay lamella. The release pattern demonstrated that the nanocomposite had a slow-release behaviour for urea dissolution. The results also suggested that the Mt type applied in the curren...