989 resultados para [NH4] exc


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Fermentation of nonabsorbed nutrients in the colon generates high concentrations of NH3/NH4+ in the colonic lumen. NH3 is a small, lipophilic neutral weak base that readily permeates almost all cell membranes, whereas its conjugate weak acid NH4+ generally crosses membranes much more slowly. It is not known how colonocytes maintain intracellular pH in the unusual acid-base environment of the colon, where permeant acid-base products of fermentation exist in high concentration. To address this issue, we hand dissected and perfused single, isolated crypts from rabbit proximal colon, adapting techniques from renal-tubule microperfusion. Crypt perfusion permits control of solutions at the apical (luminal) and basolateral (serosal) surfaces of crypt cells. We assessed apical- vs. basolateral-membrane transport of NH3/NH4+ by using fluorescent dyes and digital imaging to monitor intracellular pH of microvacuolated crypt cells as well as luminal pH. We found that, although the basolateral membranes have normal NH3/NH4+ permeability properties, there is no evidence for transport of either NH3 or NH4+ across the apical borders of these crypt cells. Disaggregating luminal mucus did not increase the transport of NH3/NH4+ across the apical border. We conclude that, compared to the basolateral membrane, the apical border of crypt colonocytes has a very low permeability-area product for NH3/NH4+. This barrier may represent an important adaptation for the survival of crypt cells in the environment of the colon.

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The present library is the second collected by Count Buturlin. The first, of which a catalog was issued at Paris in 1805, was destroyed at the burning of Moscow in 1812.

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Two-way N transfers mediated by Pisolithus sp. were examined by excluding root contact and supplying (NH4+)-N-15 or (NO3-)-N-15 to 6-month-old Eucalyptus maculata or Casuarina cunninghamiana grown in two-chambered-pots separated by 37 m screens. Mycorrhizal colonization was 35% in Eucalyptus and 66% in Casuarina (c. 29% N-2-fixation). Using an environmental scanning electron microscope, living hyphae were observed to interconnect Eucalyptus and Casuarina. Biomass and N accumulation was greatest in nodulated mycorrhizal Casuarina/mycorrhizal Eucalyptus pairs, less in nonnodulated mycorrhizal Casuarina/mycorrhizal Eucalyptus pairs, and least in nonnodulated nonmycorrhizal Casuarina/nonmycorrhizal Eucalyptus pairs. In nonnodulated mycorrhizal pairs, N transfers to Eucalyptus or to Casuarina were similar (2.4-4.1 mg per plant in either direction) and were 2.6-4.0 times greater than in nonnodulated nonmycorrhizal pairs. In nodulated mycorrhizal pairs, N transfers were greater to Eucalyptus (5-7 times) and to Casuarina (12-18 times) than in nonnodulated mycorrhizal pairs. Net transfer to Eucalyptus or to Casuarina was low in both nonnodulated nonmycorrhizal (< 0.7 mg per plant) and nonnodulated mycorrhizal pairs (< 1.1 mg per plant). In nodulated mycorrhizal pairs, net transfer to Casuarina was 26.0 mg per plant. The amount and direction of two-way mycorrhiza-mediated N transfer was increased by the presence of Pisolithus sp. and Frankia, resulting in a net N transfer from low-N-demanding Eucalyptus to high-N-demanding Casuarina.

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To determine the effects of nitrogen source on rates of net N transfer between plants connected by a common mycorrhizal network, we measured transfer of N supplied as (NH4NO3)-N-15-N-14 or (NH4NO3)-N-14-N-15 in three Casuarina/Eucalyptus treatments interconnected by a Pisolithus sp. The treatments were nonnodulated nonmycorrhizal/nonmycorrhizal; nonnodulated mycorrhizal/mycorrhizal; and nodulated mycorrhizal/mycorrhizal. Mycorrhization was 67% in Eucalyptus and 36% in Casuarina. N-2 fixation supplied 38% of the N in Casuarina. Biomass, N and N-15 contents were lowest in nonmycorrhizal plants and greatest in plants in the nodulated/mycorrhizal treatment. Nitrogen transfer was enhanced by mycorrhization and by nodulation, and was greater when N was supplied as (NH4+)-N-15 than (NO3-)-N-15. Nitrogen transfer rates were lowest in the nonmycorrhizal treatment for either N-15 source, and greatest in the nodulated, mycorrhizal treatment. Transfer was greater to Casuarina than to Eucalyptus and where ammonium rather than nitrate was the N source. Irrespective of N-15 source and of whether Casuarina or Eucalyptus was the N sink, net N transfer was low and was similar in both nonnodulated treatments. However, when Casuarina was the N sink in the nodulated, mycorrhizal treatment, net N transfer was much greater with (NH4+)-N-15 than with (NO3-)-N-15. High N demand by Casuarina resulted in greater net N transfer from the less N-demanding Eucalyptus. Net transfer of N from a non-N-2-fixing to an N-2-fixing plant may reflect the very high N demand of N-2-fixing species.

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This paper provides a method for constructing a new historical global nitrogen fertilizer application map (0.5 0.5 resolution) for the period 1961-2010 based on country-specific information from Food and Agriculture Organization statistics (FAOSTAT) and various global datasets. This new map incorporates the fraction of NH+4 (and NONO-3) in N fertilizer inputs by utilizing fertilizer species information in FAOSTAT, in which species can be categorized as NH+4 and/or NO-3-forming N fertilizers. During data processing, we applied a statistical data imputation method for the missing data (19 % of national N fertilizer consumption) in FAOSTAT. The multiple imputation method enabled us to fill gaps in the time-series data using plausible values using covariates information (year, population, GDP, and crop area). After the imputation, we downscaled the national consumption data to a gridded cropland map. Also, we applied the multiple imputation method to the available chemical fertilizer species consumption, allowing for the estimation of the NH+4/NO-3 ratio in national fertilizer consumption. In this study, the synthetic N fertilizer inputs in 2000 showed a general consistency with the existing N fertilizer map (Potter et al., 2010, doi:10.1175/2009EI288.1) in relation to the ranges of N fertilizer inputs. Globally, the estimated N fertilizer inputs based on the sum of filled data increased from 15 Tg-N to 110 Tg-N during 1961-2010. On the other hand, the global NO-3 input started to decline after the late 1980s and the fraction of NO-3 in global N fertilizer decreased consistently from 35 % to 13 % over a 50-year period. NH+4 based fertilizers are dominant in most countries; however, the NH+4/NO-3 ratio in N fertilizer inputs shows clear differences temporally and geographically. This new map can be utilized as an input data to global model studies and bring new insights for the assessment of historical terrestrial N cycling changes.

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The current-voltage characteristics of InP were investigated in (NH4)2S and KOH electrolytes. In both solutions, the observation of current peaks in the cyclic voltammetric curves was attributed to the growth of passivating films. The relationship between the peak currents and the scan rates suggests that the film formation process is diffusion controlled in both cases. The film thickness required to inhibit current flow was found to be much lower on samples anodized in the sulphide solution. Focused ion beam (FIB) secondary electron images of the surface films show that film cracking of the type reported previously for films grown in (NH4)2S is also observed for films grown in KOH. X-ray and electron diffraction measurements indicate the presence of In2O3 and InPO4 in films grown in KOH and In2S3 in films grown in (NH4)2S.

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Dentre as macroalgas capazes de absorver altas concentraes de N e P dissolvidos na gua, destaca-se a Chlorophyta Ulva lactuca, bastante adaptvel e resistente s adversidades ambientais, como grandes variaes de temperatura, salinidade, matria orgnica e metais pesados. Trata-se tambm de uma espcie bastante comum nas reas intertidais do litoral norte-riograndense. Devido a suas caractersticas ecolgicas, fisiolgicas e nutricionais, foi avaliado nesse estudo, o seu potencial como biofiltro na reduo de NH4+, NO3- e PO4-2, tanto em condies controladas como tambm em um viveiro de camaro. No experimento laboratorial, foram utilizados quatro aqurios de vidro de 30 x 20 x 20cm com 10L de gua, sendo trs aqurios experimentais contendo 20g de U. lactuca e um controle. O acrscimo de biomassa foi de 2,92g (22,92 6,29g; p < 0,05) em relao ao inculo inicial de 20g, sob temperatura (28,50 0,58C), salinidade (35,00 0,00 ), pH (8,26 0,02) e luz constante (250 &#956;mol.m2s-1). O crescimento positivo (1,78 4,38%dia-1; p < 0,05), juntamente com a alta eficincia de absoro de amnio (83%; p < 0,001), nitrato (83%; p < 0,001) e ortofosfato (53%; p < 0,001), demonstrou que, nessas condies, a Ulva lactuca absorveu os nutrientes e aumentou sua biomassa. J no experimento de campo, realizado na fazenda TECNARO, situada no municpio de Arez/RN (06 11 40 Latitude Sul, e 35 09 37 Longitude Oeste), foram utilizadas trs gaiolas de PVC, posicionadas a 12cm da superfcie da gua, cada uma com dimenses de aproximadamente 59 x 59 x 15cm, onde foram colocadas 200g de U. lactuca. O ganho de biomassa de 3g (203,00 41,02g; p < 0,001) foi muito semelhante s condies controladas, demonstrando a adaptabilidade da espcie em condies ambientais variveis, onde, apesar da temperatura pouco varivel (27,45 0,64C), houve progressiva diminuio de salinidade (25 - 15 ), devido ao perodo de fortes chuvas (34,70 23,78mm). Somado a isso, foram observados vrios fatores biolgicos interferindo no viveiro, como a presena de epfitas, organismos endofticos, fouling e a herbivoria por parte dos prprios camares. Houve aumento nas concentraes de NH4+ (4,36 1,69 &#956;mol.L-1), NO3- (0,17 0,25&#956;mol.L-1) e PO4-2 (0,41 0,13&#956;mol.L-1), coincidindo com o crescimento da espcie at a terceira semana. Todos os parmetros ambientais analisados, assim como a biomassa e a Taxa de Crescimento Relativo (TCR), obtidos no campo, apresentaram variaes altamente significativas (p < 0,001). As correlaes observadas entre biomasa e NH4+ (r = 0,82; p < 0,001) e entre biomassa e PO4-2 (r = 0,87; p < 0,001), indicam que esta espcie capaz de ter um crescimento satisfatrio nas condies eutrficas de um viveiro de camaro, sendo possvel seu uso como biofiltro.

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Dentre as macroalgas capazes de absorver altas concentraes de N e P dissolvidos na gua, destaca-se a Chlorophyta Ulva lactuca, bastante adaptvel e resistente s adversidades ambientais, como grandes variaes de temperatura, salinidade, matria orgnica e metais pesados. Trata-se tambm de uma espcie bastante comum nas reas intertidais do litoral norte-riograndense. Devido a suas caractersticas ecolgicas, fisiolgicas e nutricionais, foi avaliado nesse estudo, o seu potencial como biofiltro na reduo de NH4+, NO3- e PO4-2, tanto em condies controladas como tambm em um viveiro de camaro. No experimento laboratorial, foram utilizados quatro aqurios de vidro de 30 x 20 x 20cm com 10L de gua, sendo trs aqurios experimentais contendo 20g de U. lactuca e um controle. O acrscimo de biomassa foi de 2,92g (22,92 6,29g; p < 0,05) em relao ao inculo inicial de 20g, sob temperatura (28,50 0,58C), salinidade (35,00 0,00 ), pH (8,26 0,02) e luz constante (250 &#956;mol.m2s-1). O crescimento positivo (1,78 4,38%dia-1; p < 0,05), juntamente com a alta eficincia de absoro de amnio (83%; p < 0,001), nitrato (83%; p < 0,001) e ortofosfato (53%; p < 0,001), demonstrou que, nessas condies, a Ulva lactuca absorveu os nutrientes e aumentou sua biomassa. J no experimento de campo, realizado na fazenda TECNARO, situada no municpio de Arez/RN (06 11 40 Latitude Sul, e 35 09 37 Longitude Oeste), foram utilizadas trs gaiolas de PVC, posicionadas a 12cm da superfcie da gua, cada uma com dimenses de aproximadamente 59 x 59 x 15cm, onde foram colocadas 200g de U. lactuca. O ganho de biomassa de 3g (203,00 41,02g; p < 0,001) foi muito semelhante s condies controladas, demonstrando a adaptabilidade da espcie em condies ambientais variveis, onde, apesar da temperatura pouco varivel (27,45 0,64C), houve progressiva diminuio de salinidade (25 - 15 ), devido ao perodo de fortes chuvas (34,70 23,78mm). Somado a isso, foram observados vrios fatores biolgicos interferindo no viveiro, como a presena de epfitas, organismos endofticos, fouling e a herbivoria por parte dos prprios camares. Houve aumento nas concentraes de NH4+ (4,36 1,69 &#956;mol.L-1), NO3- (0,17 0,25&#956;mol.L-1) e PO4-2 (0,41 0,13&#956;mol.L-1), coincidindo com o crescimento da espcie at a terceira semana. Todos os parmetros ambientais analisados, assim como a biomassa e a Taxa de Crescimento Relativo (TCR), obtidos no campo, apresentaram variaes altamente significativas (p < 0,001). As correlaes observadas entre biomasa e NH4+ (r = 0,82; p < 0,001) e entre biomassa e PO4-2 (r = 0,87; p < 0,001), indicam que esta espcie capaz de ter um crescimento satisfatrio nas condies eutrficas de um viveiro de camaro, sendo possvel seu uso como biofiltro.

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Fours sets of PM10 samples were collected in three sites in SEQ from December 2002 to August 2004. Three of these sets of samples were collected by QLD EPA as a part of their regular air monitoring program at Woolloongabba, Rocklea and Eagle Farm. Half of the samples were used in this study for the analysis of water-soluble ions, which are Na+, K+, Mg2+, Ca2+, NH4 +, Cl-, NO3 -, SO4 2-, F-, Br-, NO2 -, PO4 -3 and the other half was retained by QLD EPA. The fourth set of samples was collected at Rocklea, specifically for this study. A quarter of the samples obtained from this set of samples were used to analyse water-soluble ions; a quarter of the sample was used to analyse Pb, Cu, Al, Fe, Mn and Zn; and the rests were used to analyse US EPA 16 priority PAHs. The water-soluble ions were extracted ultrasonically with water and the major watersoluble anions as well as NH4 + were analysed using IC. Na+, K+, Mg2+, Ca2+ Pb, Cu, Al, Fe, Mn and Zn were analysed using ICP-AES while PAHs were extracted by acetonitrile and analysed using HPLC. Of the analysed water-soluble ions, Cl-, NO3 -, SO4 2-, Na+, K+, Mg2+ and Ca2+ were high in concentration and determined in all the samples. F-, Br-, NO2 -, PO4 -3 and NH4 + ions were lower in concentration and determined only in some samples. Na+ and Cl- were high in all samples indicating the importance of a marine source. Principal Component Analysis (PCA) was used to examine the temporal variations of the water-soluble ions at the three sites. The results indicated that there was no major difference between the three sites. However, comparing the average concentrations of ions and Cl-/Na+ it was concluded that Woolloongabba had more marine influence than the other sites. Al, Fe and Zn were detected in all samples. Al and Fe were high in all samples indicating the significance of a source of crustal matter. Cu, Mn and Pb were in low concentrations and were determined only in some samples. The lower Pb concentrations observed in the study than in previous studies indicate that the phasing-out of leaded petrol had an appreciable impact on Pb levels in SEQ. This study reports for the first time, simultaneous data on the water-soluble, metal ion and PAH levels of PM10 aerosols in Brisbane, and provides information on the most likely sources of these chemical species. Such information can be used alongside those that already exist to formulate PM10 pollution reduction strategies for SEQ in order to protect the community from the adverse effects of PM pollution.

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Dynamic and controlled rate thermal analysis (CRTA) has been used to characterise alunites of formula [M(Al)3(SO4)2(OH)6 ] where M+ is the cations K+, Na+ or NH4+. Thermal decomposition occurs in a series of steps. (a) dehydration, (b) well defined dehydroxylation and (c) desulphation. CRTA offers a better resolution and a more detailed interpretation of water formation processes via approaching equilibrium conditions of decomposition through the elimination of the slow transfer of heat to the sample as a controlling parameter on the process of decomposition. Constant-rate decomposition processes of water formation reveal the subtle nature of dehydration and dehydroxylation.