Showing papers on "Urea published in 2006"
TL;DR: In this article, the interaction between urea/ethanolamine and starch was investigated using Fourier Transform Infrared (FT-IR) and Differential scanning calorimetry (DSC).
209 citations
TL;DR: Surprisingly, even at high concentrations of urea (8 M), the orientational dynamics of most water molecules are the same as in pure liquid water, showing that urea has a negligible effect on the hydrogen-bond dynamics of these molecules.
Abstract: We use polarization-resolved mid-infrared pump-probe spectroscopy to study the effect of urea on the structure and dynamics of water. Surprisingly, we find that, even at high concentrations of urea (8 M), the orientational dynamics of most water molecules are the same as in pure liquid water, showing that urea has a negligible effect on the hydrogen-bond dynamics of these molecules. However, a small fraction of the water molecules (approximately one water molecule per urea molecule) turns out to be strongly immobilized by urea, displaying orientational dynamics that are more than six times slower than in bulk water. A likely explanation is that these water molecules are tightly associated with urea, forming specific urea–water complexes. We discuss these results in light of the protein denaturing ability of aqueous urea.
183 citations
169 citations
TL;DR: In this article, Nitrous oxide, nitric oxide and denitrification losses from an irrigated soil amended with organic fertilizers with different soluble organic carbon fractions and ammonium contents were studied in a field study covering the growing season of potato.
Abstract: Nitrous oxide, nitric oxide and denitrification losses from an irrigated soil amended with organic fertilizers with different soluble organic carbon fractions and ammonium contents were studied in a field study covering the growing season of potato ( Solanum tuberosum ) Untreated pig slurry (IPS) with and without the nitrification inhibitor dicyandiamide (DCD), digested thin fraction of pig slurry (DTP), composted solid fraction of pig slurry (CP) and composted municipal solid waste (MSW) mixed with urea were applied at a rate of 175 kg available N ha −1 , and emissions were compared with those from urea (U) and a control treatment without any added N fertilizer (Control) The cumulative denitrification losses correlated significantly with the soluble carbohydrates, dissolved N and total C added Added dissolved organic C (DOC) and dissolved N affected the N 2 O/N 2 ratio, and a lower ratio was observed for organic fertilizers than from urea or unfertilized controls The proportion of N 2 O produced from nitrification was higher from urea than from organic fertilizers Accumulated N 2 O losses during the crop season ranged from 369 to 731 kg N 2 O–N ha −1 for control and urea, respectively, whereas NO losses ranged from 0005 to 024 kg NO–N ha −1 , respectively Digested thin fraction of pig slurry compared to IPS mitigated the total N 2 O emission by 48% and the denitrification rate by 33%, but did not influence NO emissions Composted pig slurry compared to untreated pig slurry increased the N 2 O emission by 40% and NO emission by 55%, but reduced the denitrification losses (34%) DCD partially inhibited nitrification rates and reduced N 2 O and NO emissions from pig slurry by at least 83% and 77%, respectively MSW+U, with a C:N ratio higher than that of the composted pig slurry, produced the largest denitrification losses (333 kg N ha −1 ), although N 2 O and NO emissions were lower than for the U and CP treatments This work has shown that for an irrigated clay loam soil additions of treated organic fertilizers can mitigate the emissions of the atmospheric pollutants NO and N 2 O in comparison with urea
164 citations
TL;DR: The transport of nitrogen across the rumin epithelium is characterized by absorption of ammonia from the rumen and by an influx of urea into the rumens, both of which are large and exhibit wide variation.
Abstract: The transport of nitrogen across the rumen epithelium is characterized by absorption of ammonia from the rumen and by an influx of urea into the rumen. The transport rates of both compounds are large and exhibit wide variation. The transport of ammonia occurs in two forms: in the lipophilic form as NH3, the magnitude of which is linearly related to the pH in the ruminal fluid at pH values above 7, while at a physiological pH of 6.5 or lower, ammonia is predominantly absorbed as NH4+ via putative potassium channels in the apical membrane. The uptake of NH4+ depends on the potential difference of the apical membrane, Pda, and shows competition with K uptake. The pathway for basolateral exit of NH4+ is unknown. Hence, the relative transport rates of NH3 or NH4+ are determined by the ruminal pH according to the Henderson-Hasselbalch equation. Transport of ammonia interacts with the transport of Na and Mg mainly via changes of the intracellular pH. Urea recycling into the rumen has been known for many years and the transport across the rumen epithelium is mediated via urea transporters in the luminal and basolateral membrane of the epithelium. Transport of urea occurs by simple diffusion, but is highly variable. A significant increase of urea influx is caused by the fermentation products CO2 and short-chain fatty acids. Conversely, there is some evidence of inhibition of urea influx by ruminal ammonia. The underlying mechanisms of this modulation of urea transport are unknown, but of considerable nutritional importance, and future research should be directed to this aspect of ruminal transport.
152 citations
TL;DR: The amounts of amino acids excreted increased in relation to the severity of growth impairment by ammonium, suggesting that amino acid excretion is used by yeast for ammonium detoxification.
Abstract: DNA microarray analysis of gene expression in steady-state chemostat cultures limited for potassium revealed a surprising connection between potassium and ammonium: potassium limits growth only when ammonium is the nitrogen source. Under potassium limitation, ammonium appears to be toxic for Saccharomyces cerevisiae. This ammonium toxicity, which appears to occur by leakage of ammonium through potassium channels, is recapitulated under high-potassium conditions by over-expression of ammonium transporters. Although ammonium toxicity is well established in metazoans, it has never been reported for yeast. To characterize the response to ammonium toxicity, we examined the filtrates of these cultures for compounds whose excretion might serve to detoxify the ammonium (such as urea in mammals). Using liquid chromatography–tandem mass spectrometry to assay for a wide array of metabolites, we detected excreted amino acids. The amounts of amino acids excreted increased in relation to the severity of growth impairment by ammonium, suggesting that amino acid excretion is used by yeast for ammonium detoxification.
141 citations
TL;DR: In this paper, metal oxides were used for synthesis of ethylene carbonate from urea and ethylene glycol, and the results indicated that the catalysts with appropriate acid and base properties were favorable to the synthesis of cyclic carbonate.
132 citations
126 citations
TL;DR: Current knowledge on the membrane localization, energetization and regulation of these two types of urea transporters are summarized and their possible physiological roles in planta are discussed.
Abstract: Urea is a soil nitrogen form available to plant roots and a secondary nitrogen metabolite liberated in plant cells. Based on growth complementation of yeast mutants and “in-silico analysis”, two plant families have been identified and partially characterized that mediate membrane transport of urea in heterologous expression systems. AtDUR3 is a single Arabidopsis gene belonging to the sodium solute symporter family that cotransports urea with protons at high affinity, while members of the tonoplast intrinsic protein (TIP) subfamily of aquaporins transport urea in a channel-like manner. The following review summarizes current knowledge on the membrane localization, energetization and regulation of these two types of urea transporters and discusses their possible physiological roles in planta.
125 citations
TL;DR: The results of the present work indicated that the DSWU would find good application in agriculture and horticulture, especially in drought-prone areas where the availability of water is insufficient.
Abstract: A double-coated, slow-release, and water-retention urea fertilizer (DSWU) was prepared by cross-linked poly(acrylic acid)-containing urea (PAAU) (the outer coating), polystyrene (PS) (the inner coating), and urea granule (the core). Elemental analysis results showed that the nitrogen content of the product was 33.6 wt %. The outer coating (PAAU) regulated the nitrogen release rate and protected the inner coating from damage. The slow-release property of the product was investigated in water and in soil. The possible mechanism of nitrogen release was proposed. The influences of PS coating percentage, temperature, water absorbency, and pH on the release of nitrogen were also investigated. It was found that PS coating percentage, temperature, and water absorbency had a significant influence on the release of nitrogen. However, the pH had no effect. The water-retention property of the product was also investigated. The results showed that the product not only had a good slow-release property but also excellent water-retention capacity, which could effectively improve the utilization of fertilizer and water resources. The results of the present work indicated that the DSWU would find good application in agriculture and horticulture, especially in drought-prone areas where the availability of water is insufficient.
123 citations
TL;DR: The rise in the hepatic activity of protein-metabolising enzymes in the fish fed high protein diets denoted effective use of dietary amino acids for growth and as a substrate for gluconeogenesis.
Abstract: This manuscript reports changes in key enzymes and metabolites related to protein metabolism and nitrogen excretion in the liver of juveniles jundia (Rhamdia quelen) fed on isocaloric diets containing 20%, 27%, 34% and 41% of crude protein. The hepatic activity of alanine aminotransferase (ALAT), aspartate aminotransferase (ASAT), glutamate dehydrogenase (GDH), and arginase (ARG) increased with the content of protein in the diet, and the ratios among the aminotransferases and GDH allowed evaluating metabolic preference. The concentration of free amino acids, ammonia and urea also rose with the dietary protein content. Increase of plasma urea and ammonia was the resultant effect of over amino acids catabolism as consequence of dietary protein surplus. Since the increase of protein in the diets resulted in weight gain, the rise in the hepatic activity of protein-metabolising enzymes in the fish fed high protein diets denoted effective use of dietary amino acids for growth and as a substrate for gluconeogenesis. Analysis of changes on metabolite levels and key enzyme activities in amino acid metabolism is proposed as a tool for assessing the proper balance of diet macronutrients.
TL;DR: In this article, the X-ray crystal structures of N,N'-bis(3-pyridyl)urea 3 and some of its derivatives were analyzed and it was shown that the urea tape is absent in these structures because the CO acceptor is weakened by two intramolecular C−H···Ourea interactions (synthon III) in a planar molecular conformation.
Abstract: The urea tape α-network of bifurcated N−H···O hydrogen bonds is a common motif in diaryl ureas and their molecular complexes. We analyzed the X-ray crystal structures of N,N‘-bis(3-pyridyl)urea 3 and some of its derivatives: hydrates of stoichiometry 3·(4/3)H2O and 3·2H2O, cocrystals 3·SA and 3·FA·H2O with succinic acid and fumaric acid, bis pyridine N-oxide 8, and bis N-methylpyridinium iodide 9. Crystal packing in pyridyl urea structures is directed by N−H···Npyridyl, N−H···Owater, N−H···Oacid, and N−H···I- hydrogen bonds instead of the common one-dimensional N−H···Ourea tape. We postulated that the urea tape is absent in these structures because the CO acceptor is weakened by two intramolecular C−H···Ourea interactions (synthon III) in a planar molecular conformation. Electrostatic surface potential (ESP) charges (DFT-B3LYP/6-31G*) showed that the C−H···O interactions sufficiently reduce the electron density at the urea O, and so other electronegative atoms, such as pyridyl N, H2O, COOH, and I-, becom...
TL;DR: The digestion method avoids the need to remove urea before HPLC/MS/MS analysis or methylation and IMAC, increasing throughput while reducing sample loss and contamination from sample handling, and should be valuable for proteomics studies.
Abstract: Proteolytic digestion of a complicated protein mixture from an organelle or whole-cell lysate is usually carried out in a dilute solution of a denaturing buffer, such as 1-2 M urea. Urea must be subsequently removed by C18 beads before downstream analysis such as HPLC/MS/MS or complete methylation followed by IMAC isolation of phosphopeptides. Here we describe a procedure for digesting a complicated protein mixture in the absence of denaturants. Proteins in the mixture are precipitated with trichloroacetic acid/acetone for denaturation and salt removal and resuspended in NH4HCO3 buffer. After trypsinolysis, the resulting peptides are not contaminated by urea or other nonvolatile salts and can be dried in a SpeedVac to remove NH4HCO3. When this protocol was applied to an extract of A431 cells, 96.8% of the tryptic peptides were completely digested (i.e., had no missed cleavage sites), in contrast to 87.3% of those produced by digestion in urea buffer. We successfully applied this digestion method to analysis of the phosphoproteome of adiposomes from HeLa cells, identifying 33 phosphorylation sites in 28 different proteins. Our digestion method avoids the need to remove urea before HPLC/MS/MS analysis or methylation and IMAC, increasing throughput while reducing sample loss and contamination from sample handling. We believe that this method should be valuable for proteomics studies.
TL;DR: A chiral tris(urea) organogelator gels dmso-water and methanol-water mixtures at low weight percent resulting in fully crystalline material characterised by X-ray crystallography.
TL;DR: In this article, a new Naphthalene derivative with two urea groups, 1,8-bis[ N -( o -methoxyphenyl)ureido]naphthalenes (BMPUN ), was synthesized for detecting Cu(II) ratiometrically.
TL;DR: It is indicated that single dose, high rate, water soluble N applications to mature turfgrass stands should be avoided to minimize the potential for NO 3 -N leaching.
Abstract: Research on nitrate-nitrogen (NO 3 -N) leaching in turfgrass indicates that, in most cases, leaching poses little risk to the environment. Most of the research was conducted on sites that were recently established, and the potential for greater NO 3 -N leaching from mature turf sites is unknown. The fate of nitrogen (N) was examined for a 10-yr-old Kentucky bluegrass (Poa pratensis L.) turf using intact monolith lysimeters and microplots. From October 2000 through July 2002, half of the lysimeters and microplots were treated annually with urea at a high rate of 245 kg N ha -1 (49 kg N ha -1 application -1 ). The remaining lysimeters and microplots were treated annually with urea at a low rate of 98 kg N ha -1 (24.5 kg N ha -1 application -1 ). The Oct. 2000 urea application was made with 15 N double-labeled urea to facilitate fertilizer identification among clippings, verdure, thatch, soil, roots, and leachate. The average total recovery of applied labeled fertilizer nitrogen (LFN) for the low and high N rates was 78 and 74%, respectively. NO 3 -N concentrations in leachate for the low N rate were typically below 5 mg L -1 . For the high N rate, NO 3 -N concentrations in leachate were often greater than 20 mg L -1 . Over approximately 2 yr, 1 and 11% of LFN was recovered in leachate for the low and high N rates, respectively. This research indicates that single dose, high rate, water soluble N applications (49 kg N ha -1 application -1 ) to mature turfgrass stands should be avoided to minimize the potential for NO 3 -N leaching.
TL;DR: Beta-(1-->6)-linked pseudodi- and pseudotrisaccharides incorporating alternating pseudoamide-type (urea, thiourea, guanidine) intersaccharide bridges have been prepared and evaluated as phosphate binders in water.
Abstract: β-(1→6)-Linked pseudodi- and pseudotrisaccharides incorporating alternating pseudoamide-type (urea, thiourea, guanidine) intersaccharide bridges have been prepared and evaluated as phosphate binder
TL;DR: It is suggested that N conservation is a high priority in this elasmobranch and that feeding promotes ureogenesis and growth.
Abstract: Urea not only is utilized as a major osmolyte in marine elasmobranchs but also constitutes their main nitrogenous waste. This study investigated the effect of feeding, and thus elevated nitrogen intake, on nitrogen metabolism in the Pacific spiny dogfish Squalus acanthias. We determined the activities of ornithine urea cycle (O‐UC) and related enzymes in liver and nonhepatic tissues. Carbamoyl phosphate synthetase III (the rate‐limiting enzyme of the O‐UC) activity in muscle is high compared with liver, and the activities in both tissues increased after feeding. The contribution of muscle to urea synthesis in the dogfish body appears to be much larger than that of liver when body mass is considered. Furthermore, enhanced activities of the O‐UC and related enzymes (glutamine synthetase, ornithine transcarbamoylase, arginase) were seen after feeding in both liver and muscle and were accompanied by delayed increases in plasma urea, trimethylamine oxide, total free amino acids, alanine, and chloride ...
TL;DR: The interaction of minerals with amino acids and/or urea was key to optimizing ethanol production by cells in both growing and stationary-phase cultures.
Abstract: Nutrition-based strategies to optimize xylose to ethanol conversion by Pichia stipitis were identified in growing and stationary-phase cultures provided with a defined medium varied in nitrogen, vitamin, purine/pyrimidine, and mineral content via full or partial factorial designs. It is surprising to note that stationary-phase cultures were unable to ferment xylose (or glucose) to ethanol without the addition of a nitrogen source, such as amino acids. Ethanol accumulation increased with arginine, alanine, aspartic acid, glutamic acid, glycine, histidine, leucine, and tyrosine, but declined with isoleucine. Ethanol production from 150 g/l xylose was maximized (61±9 g/l) by providing C:N in the vicinity of ∼57–126:1 and optimizing the combination of urea and amino acids to supply 40–80 % nitrogen from urea and 60–20 % from amino acids (casamino acids supplemented with tryptophan and cysteine). When either urea or amino acids were used as sole nitrogen source, ethanol accumulation dropped to 11 or 24 g/l, respectively, from the maximum of 46 g/l for the optimal nitrogen combination. The interaction of minerals with amino acids and/or urea was key to optimizing ethanol production by cells in both growing and stationary-phase cultures. In nongrowing cultures supplied with nitrogen as amino acids, ethanol concentration increased from 24 to 54 g/l with the addition of an optimized mineral supplement of Fe, Mn, Mg, Ca, Zn, and others.
TL;DR: In this paper, the synthesis of chromium oxides by solution combustion synthesis was investigated; the effect of different reaction parameters, such as fuel richness, stoichiometry and fuel leanness, was evaluated; such parameters were modified by changing the reagents and the fuel/oxidant ratio.
Abstract: The synthesis of chromium oxides by solution combustion synthesis was investigated. Ammonium dichromate, glycine, urea and ammonium nitrate dissolved in aqueous solution were used as the precursors of the oxides. The effect of different reaction parameters, such as fuel richness, stoichiometry and fuel leanness was evaluated; such parameters were modified by changing the reagents and the fuel/oxidant ratio. Amorphous CrO3 and crystalline Cr2O3 were synthesized. The results suggest that glycine is a better complexing/combustible agent for ammonium dichromate than urea. Addition of extra ammonium nitrate to stoichiometric compositions improved the specific surface area and reduced the crystallite size. The smallest crystallite size (≈20 nm) of Cr2O3 was obtained with glycine as fuel/complexant agent in fuel-lean mixtures. The highest specific surface area (63 m2/g) was observed with urea in fuel-rich mixtures, forming amorphous CrO3.
TL;DR: It is believed that the facilitated diffusion urea transporter (UT) gene family has undergone major evolutionary changes, likely in association with the role of urea transport in the evolution of terrestriality in the vertebrates.
Abstract: This review summarizes what is currently known about urea transporters in fishes in the context of their physiology and evolution within the vertebrates. The existence of urea transporters has been investigated in red blood cells and hepatocytes of fish as well as in renal and branchial cells. Little is known about urea transport in red blood cells and hepatocytes, in fact, urea transporters are not believed to be present in the erythrocytes of elasmobranchs nor in teleost fish. What little physiological evidence there is for urea transport across fish hepatocytes is not supported by molecular evidence and could be explained by other transporters. In contrast, early findings on elasmobranch renal urea transporters were the impetus for research in other organisms. Urea transport in both the elasmobranch kidney and gill functions to retain urea within the animal against a massive concentration gradient with the environment. Information on branchial and renal urea transporters in teleost fish is recent in comparison but in teleosts urea transporters appear to function for excretion and not retention as in elasmobranchs. The presence of urea transporters in fish that produce a copious amount of urea, such as elasmobranchs and ureotelic teleosts, is reasonable. However, the existence of urea transporters in ammoniotelic fish is curious and could likely be due to their ability to manufacture urea early in life as a means to avoid ammonia toxicity. It is believed that the facilitated diffusion urea transporter (UT) gene family has undergone major evolutionary changes, likely in association with the role of urea transport in the evolution of terrestriality in the vertebrates.
TL;DR: A phylogenetic explanation for the distribution of TMAO synthesis in elasmobranchs is proposed and it is suggested that activation of liver betaine aldehyde dehydrogenase, relative to choline dehydrogenases, coincides with betaine accumulation in elasmsobranching.
Abstract: We compared levels of the major organic osmolytes in the muscle of elasmobranchs, including the methylamines trimethylamine oxide (TMAO), betaine and sarcosine as well as the beta-amino acids taurine and beta-alanine, and the activities of enzymes of methylamine synthesis (betaine and TMAO) in species with a wide range of urea contents. Four marine, a euryhaline in freshwater (Dasyatis sabina), and two freshwater species, one that accumulates urea (Himantura signifer) and one that does not (Potamotrygon motoro), were analyzed. Urea contents in muscle ranged from 229-352 micromol g-1 in marine species to 2.0 micromol g-1 in P. motoro. Marine elasmobranchs preferentially accumulate methylamines, possibly to counteract urea effects on macromolecules, whereas the freshwater species with lower urea levels accumulate the beta-amino acid taurine as the major non-urea osmolyte. A strong correlation (r2=0.84, P<0.001) with a slope of 0.40 was found between muscle urea content and the combined total methylamines plus total beta-amino acids, supporting the hypothesis that ;non-urea' osmolytes are specifically maintained at an approximately 2:1 ratio with urea in the muscle of elasmobranchs. All species examined had measurable synthetic capacity for betaine in the liver but only one species had detectable TMAO synthetic capacity. We propose a phylogenetic explanation for the distribution of TMAO synthesis in elasmobranchs and suggest that activation of liver betaine aldehyde dehydrogenase, relative to choline dehydrogenase, coincides with betaine accumulation in elasmobranchs. The latter relationship may be important in maintaining methylamine levels during periods of low dietary TMAO intake for species lacking TMAO synthesis.
TL;DR: Exposure and potential dose of adult and children exposed to indoor/outdoor ammonia in summer and in winter are calculated and evaluated by using Scenario Evaluation Approach and indicated that high air exchange rate leads to decreased ammonia concentration, and elevation of temperature causes increasing ammonia concentration and volatilizing rate in chamber.
TL;DR: In this article, the effects of dietary urea-calcium (a slow rumen-release urea source) on absorption of ammonia N from the gut and urea N production in the liver were evaluated with Angus or Holstein steers.
TL;DR: This study confirms in humans an age-related increase in plasma urea levels and no correlation between plasma creatinine and age and observations incited a comparison of biochemical profiles from younger and older patients with the syndrome of inappropriate secretion of antidiuretic hormone.
Abstract: This study confirms in humans an age-related increase in plasma urea levels (r = 0.62; P < 0.001; y = 0.229x + 18.26) and no correlation between plasma creatinine and age (r = 0.06; NS). Fractional urea excretion (FE urea) decreases with age (r = -0.41; P < 0.001; y = -0.226x + 55). Comparing urea and creatinine clearances, measured in 19 young and in 15 old women, a larger decrease of urea clearance (-56%) compared with the creatinine clearance (-43%) was observed as expected, explaining the lower FE urea in the elderly. In old women, the daily urea excretion was 27% and the daily creatinine excretion was 42% lower than in young women. An age-related decrease of same magnitude in both creatinine production and creatinine clearance explains why plasma creatinine remains stable with increasing age. The observation of a more important decrease in urea clearance (56%) than in urea production (27%) in older women led to an expected increase in plasma urea of 29%. These observations incited a comparison of biochemical profiles from younger and older patients with the syndrome of inappropriate secretion of antidiuretic hormone (SIADH). Young patients with SIADH present lower mean plasma urea (18 +/- 8 mg/dl) and higher mean FE urea (58 +/- 14%), compared with both young control subjects (mean plasma urea 27 +/- 7 mg/dl; mean FE urea 46 +/- 10%) and old patients with SIADH (mean plasma urea 29 +/- 8 mg/dl; mean FE urea 44 +/- 15%). Physicians must realize that frankly low plasma urea values and high FE urea values can be expected only in young patients with SIADH, whereas old patients with SIADH will present values of plasma urea and FE urea in the same range than young control subjects. However, old patients with SIADH show still lower mean plasma urea values and higher mean FE urea values, compared with old control subjects (mean plasma urea 39 +/- 8 mg/dl; mean FE urea 36 +/- 9%), in whom plasma urea values between 40 and 50 mg/dl must be considered as usual.
TL;DR: In this paper, the effect of four different, urea-triple superphosphate (TSP)-humic acid-zeolite, mixtures on NH 3 loss, and soil ammonium and nitrate contents, with loss from surface-applied urea without additives.
Abstract: Ammonia losses from soil following fertilization with urea may be large. This laboratory study compared the effect of four different, urea-triple superphosphate (TSP)-humic acid-zeolite, mixtures on NH 3 loss, and soil ammonium and nitrate contents, with loss from surface-applied urea without additives. The soil was a sandy clay loam Typic Kandiudult (Bungor Series). The mixtures significantly reduced NH 3 loss by between 32 and 61% compared with straight urea (46% N) with larger reductions with higher rates of humic acid (0.75 and 1 g kg -1 of soil) and zeolite (0.75 and 1 g kg -1 of soil). All the mixtures of acidic P fertilizer, humic acid and zeolite with urea significantly increased soil NH 4 and NO 3 contents, increased soil-exchangeable Ca, K and Mg, and benefited the formation of NH 4 over NH 3 compared with urea without additives. The increase in soil-exchangeable cations, and temporary reduction of soil pH may have retarded urea hydrolysis in the microsite immediately around the fertilizer. It may be possible to improve the efficiency of urea surface-applied to high value crops by the addition of TSP, humic acid and zeolite.
TL;DR: In this paper, two different iron exchanged zeolites were studied for the hydrolysis of isocyanic acid (HNCO) to ammonia, which is an important intermediate step in the selective catalytic reduction (SCR) of NO with urea.
TL;DR: Comparison of urea uptake rates with nitrate or ammonium uptake rates for the same S. pistillata species, at in situ concentrations, showed that urea is preferred to nitrate and may therefore be an important source of nitrogen for scleractinian corals.
Patent•
19 Oct 2006
TL;DR: In this paper, the authors proposed a solution to prevent the freezing of reducing agent such as urea water or the like to suppress the breakage of components of a reducing agent supply system.
Abstract: PROBLEM TO BE SOLVED: To prevent the freezing of reducing agent such as urea water or the like to suppress the breakage of components of a reducing agent supply system. SOLUTION: A DPF 12 and an SCR catalyst 13 are disposed to an exhaust pipe 11, and a urea water addition valve 15 for adding and supplying the urea water to the exhaust pipe 11 is disposed between the DPF 12 and the SCR catalyst 13. In constitution of the urea water supply system, urea water of predetermined concentration is stored in the urea water tank 21, and a urea water pump 22 is disposed in the tank 21. The urea water pump 22 can rotate in normal and reverse directions. A urea water supply pipe 23 is connected to the urea water pump 22. After stop of an engine, an ECU 30 drives the urea water pump 22 with a state where urea water is sucked again (a reverse rotation drive state) different from a normal urea water discharge state (a normal rotation drive state). Therefore, the urea water remaining in the urea water addition valve 15 or the urea water supply pipe 23 is collected in the urea water tank 21. COPYRIGHT: (C)2008,JPO&INPIT
TL;DR: In this article, the effect of urea on the physicochemical (pH and conductivity) and rheological properties of the chitosan- β -GP system was investigated.