Efeito da proporcao NH4+/NO3- na distribuicao de nitrato e na atividade in vitro da redutase do nitrato de plantas de Panicum maximum.

O objetivo deste trabalho foi estudar os efeitos da nutricao nitrica e amoniacal na distribuicao de nitrato e na atividade in vitro da redutase do nitrato em plantas de capim coloniao ( Panicum maximum Jacq.). as plantas receberam 7 mM de nitrogenio nas forma N- NH4 +, N-NO3- ou combinadas nas seguintes proporcoes 0/100, 25/75, 50/50, 75/25 e 100/0. A extracao enzigmatica foi feita em Tris-HCI 50mM pH 7,5, EDTA 0,5 mM e b-mercaptoetanol 10mM, e para o ensaio utilizou-se 200 mmoles de Tris-HCI pH 7,5, 20 mmoles KNO3, 0,1 mmol NADH e 0,1 mL de Triton X-100 1% no volume final de 2,0 mL. A concentracao de nitrato foi levemente superior na parte aerea quando as plantas receberam ambas as formas de nitrogenio, e na raiz seta decresceu com o aumento da proporcao de aminio. A atividade in vitro de redutase do nitrato so foi observada nas folhas e foi maior quando as plantas receberam ambas as formas de nitrogenio. Os resultados sugerem um efeito estimulador do amonio no tranporte de nitrato e na atividade de redutase do nitrato quando NO3- esta presente.

Assimilacao do nitrogenio pelas plantas de panicum maximum, cv. Vencedor, submetidas a diferentes proporcoes NH4+/NO3-.

Visando a elucidar alguns aspectos do metabolismo do nitrogenio por plantas de Panicum maximum, estudaram-se os efeitos da proporcao NH +4/NO-3 na variacao do pH das solucoes nutritivas de tratamento, no acumulo de materia seca e na distribuicaoo de nitrogenio na planta. Para tal, as plantas foram cultivadas em camara de crescimento na solucao nutritiva (pH 5,5) completa, contendo nitrogenio somente na forma nitrica. Aos 25 dias depois da germinacao, as plantas foram submetidas a 100 ppm de nitrogenio fornecido nas formas nitrica e amoniacal ou amonical, nas seguintes proporcoes 0/100,25/75,50/50,75/25 e 100/0, durante quatro dias. O pH das solucoes nutritivas foi medido e corrigido diariamente. Os resultados demostraram que o pH aumentou na presenca exclusiva de nitrato (pH 6,5) e decresceu na presenca exclusiva de amonio (pH 3,5). Na presenca de ambas as formas de nitrogenio, o pH permaneceu em torno de 5,0 nos dois primeiros dias entao diminui para cerca de 4,5 nos dias subsequentes. Esses resultados indicam que as plantas de Panicum maximum absorveram o nitrato, inicialmente, porem com o tempo adaptaram-se a presenca de amonio e tenderam a absorver ambas as formas. As plantas que receberam nitrato, combinados ou não com amonio, apresentaram o peso da materia seca, N-total e N-soluvel total superiores as que receberam somente amonio como fonte de N, havenso pequena tendencia de maior acumulo na presenca de ambas as fontes. No tratamento 100% de amonio, pN-total e o N-soluvel total diminuiram apreciavelmente, indicando baixa capacidade de essa especie utilizar amonio como fonte única de nitrogenio. Os resultados indicam que, embora as plantas possa absorver as duas formas de nitrogenio, a combinacao entre ambas parece ser a forma ideal para o crescimento das mesmas.

The persistence of the HgCl2 molecule in five new compounds in the system (NH4)(w)HgxCly(H2O)(z) with w : x : y : z=1 : 5 : 11 : 0, 2 : 3 : 8 : 1, 4 : 3 : 10 : 2, 2 : 1 : 4 : 1, and 10 : 3 : 16 : 0

Five new compounds in the system (NH4)Cl/HgCl2/H2O have been obtained as colourless single crystals, (NH4)Hg5Cl11, (NH4)(2)Hg3Cl8(H2O), (NH4)(4)Hg3Cl10(H2O)(2), (NH4)(2)HgCl4(H2O), and (NH4)(10)Hg3Cl16. In all of these, as in HgCl2 itself, (almost) linear HgCl2 molecules persist with Hg-Cl distances varying from 229 to 236 pm. In (NH4)(10)Hg3Cl16 there are also tetrahedra [HgCl4] with d(Hg-Cl) = 247 pm present. If larger Hg-Cl distances (of up to 340 pm) are considered as belonging to the coordination sphere of Hg-II, the structures may be described as consisting of isolated octahedra and tetrahedra as in (NH4)(10)Hg3Cl16, edge-connected chains as in (NH4)(2)HgCl4(H2O), edge-connected chains and layers of octahedra as in (NH4)(4)Hg3Cl10(H2O)(2), corrugated layers of edge-connected octahedra as in (NH4)(2)Hg3Cl8(H2O), and, finally, a three-dimensional network of connected six- and seven-coordinate Hg-Cl polyhedra as in (NH4)Hg5Cl11. The water molecules are never attached to Hg-II. The (NH4)(+) cations, and sometimes Cl- anions, play a role for electroneutrality only.

Tetrahedra and vertex-sharing double tetrahedra in the ammonium iodomercurates(II) (NH4)(7)[HgI4](2)[Hg2I7](H2O) and (NH4)(3)[Hg2I7]

The new ammonium iodomercurates(II), (NH4)(7)[HgI4](2)[Hg2I7](H2O) (1) and (NH4)(3)[Hg2I7] (2) contain isolated tetrahedra and vertex-sharing double tetrahedra as the anions. The crystal structures were determined from single-crystal X-ray diffraction data: 1: orthorhombic, Pnma (no. 62), a = 2175.9(2), b = 1781.8(2), c = 1256.2(2) pm, Z = 4. R-1 [I-0 > 2 sigma(I-0)] = 0.0520; 2: monoclinic, P2(1)/c (no. 14), a = 1259.0(2), b = 773.2(1), c = 2172.4(3) pm, beta = 101.18(2)degrees, Z = 4, R, [I-0 > 2 sigma(I-0)] = 0.0308.

The ammonium bromomercurates(II) (NH4)Hg5Br11 and (NH4)(4)HgBr6

The crystal structures of two ammonium bromomercurates(II), (NH4)Hg5Br11 (1) and (NH4)(4)HgBr6 (2), were determined from single-crystal X-ray diffraction data: 1: monoclinic, C2/m (no. 12), a = 1231.3(3), b = 1517.4(3), c = 680.4(2) pm, beta = 118.78(2)degrees, Z = 2, R-1 = 0.0391 for I-0 > 2 sigma(I-0); 2: tetragonal, P4/mnc (no. 128), a = 925.6(1), c = 887.2(1) pm, Z = 2, R-1 = 0.0370 for I(0 >)2a(I-0). According to (NH4)Br[HgBr2](5) and (NH4)(4)Br-4[HgBr2] they both contain [Br-Hg-Br] molecules. Additional bromide ions are only loosely attached to the mercury atoms, however involved in (NH4)(+)-Br- bonding.

Formation of NH4[Hg-3(NH)(2)](NO3)(3) and transformation to [Hg2N](NO3)

NH4[Hg-3(NH)(2)](NO3)(3) (1) and [Hg2N](NO3) (2) are obtained from cone. aqueous ammonia solutions of Hg(NO3)(2) at ambient temperature and under hydrothermal conditions at 180 degreesC, respectively, as colourless and dark yellow to light brown single crystals. The crystal structures {NH4[Hg-3(NH)(2)](NO3)(3): cubic, P4(I)32, a = 1030.4(2) pm, Z = 4, R-all = 0.028; [Hg2N](NO3): tetragonal, P4(3)2(1)2, a = 1540.4(1), c = 909.8(1) pm, Z = 4, R-all = 0.054} have been determined from single crystal data. Both exhibit network type structures in which [HNHg3] and [NHg4] tetrahedra of the partial structures of 1 and 2 are connected via three and four vertices, respectively. 1 transforms at about 270 degreesC in a straightforward reaction to 2 whereby the decomposition products of NH4NO3 are set free. 2 decomposes at about 380 degreesC forming yellow HgO. Most certainly, I is identical with a mineral previously analyzed as

Reactivity of ammonium chloride/mercuric chloride mixtures with monel containers. The new compounds (NH4)(2)(NH3)(x)[Ni(NH3)(2)Cl-4] and (NH4)(5)Cl-2[CuCl2][CuCl4]

Ammonium chloride/mercuric chloride mixtures (molar ratio 2: 1) react at 350degreesC with Monel (Cu68Ni32) to yield (NH4)NiCl3 and mercury and copper amalgam, respectively. With larger amounts of (NH4)Cl in the reaction mixture, dark green (NH4)(2)(NH3)(x)[Ni(NH3)(2)Cl-4] (x approximate to 0.77) (1) is also formed as a main product. Light blue crystals of the mixed-valent copper(I,II) chloride (NH4)(5)Cl-5[CuCl2][CuCl4] (2) were obtained as a minor byproduct from a 4:1 reaction mixture. The crystal structures were determined from single crystal X-ray data; (1): tetragonal, I4/mmm, a = 770.9(1), e = 794.2(2) pm, 190 reflections, R-1 = 0.0263; (2): tetragonal, I4/mcm, a = 874.8(1), c = 2329.2(3) pm, 451 reflections, R-1 = 0.0736. In (1) Ni2+ resides in trans-[Ni(NH3)(2)Cl-4](2-) octahedra, and in (2) copper(l) is linearly two-coordinated in ECUC121- and copper(II) resides in a flattened tetrahedron [CuCl4](2-) with a tetrahedricity of 89%. (C) 2001 Elsevier Science.

Ammonium mercury(II) dichloride nitrate, (NH4)(2)HgCl2(NO3)(2)

The title compound, (NH4)(2)HgCl2 (NO3)(2), is a double salt of HgCl2 and NH4NO3 and can also be written as `HgCl2.2NH(4)NO(3)'. The structure contains HgCl2 units which are connected by nitrate groups, through long links of ca. 2.90 Angstrom, to give chains running along [010]. All atoms apart from the two oxygen atoms are located on a mirror plane perpendicular to the b axis. The coordination around mercury is a distorted hexagonal bipyramid.

COD and NH4-N Estimation in the Inflow of Wastewater Treatment Plants using Machine Learning Techniques

The in-line measurement of COD and NH4-N in the WWTP inflow is crucial for the timely monitoring of biological wastewater treatment processes and for the development of advanced control strategies for optimized WWTP operation. As a direct measurement of COD and NH4-N requires expensive and high maintenance in-line probes or analyzers, an approach estimating COD and NH4-N based on standard and spectroscopic in-line inflow measurement systems using Machine Learning Techniques is presented in this paper. The results show that COD estimation using Radom Forest Regression with a normalized MSE of 0.3, which is sufficiently accurate for practical applications, can be achieved using only standard in-line measurements. In the case of NH4-N, a good estimation using Partial Least Squares Regression with a normalized MSE of 0.16 is only possible based on a combination of standard and spectroscopic in-line measurements. Furthermore, the comparison of regression and classification methods shows that both methods perform equally well in most cases.

DC electrical conductivity and phase transitions in (NH4)3H(SO4)2

Four distinct peaks are observed at 140, -26, -132 and -140°C in the sigma x* against T-1 plot between 200 and - 196°C for (NH4)3H(SO4)2, corresponding to four different phase transitions of which the one at -26°C is reported here for the first time. Data on doped samples reveal the charge transport mechanism in the crystal.