989 resultados para [NH4] exc
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[Notice biographique. Hassan Ali Khan Kboudvendi (franais). 1861]
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Four distinct peaks are observed at 140, -26, -132 and -140C in the sigma x* against T-1 plot between 200 and - 196C for (NH4)3H(SO4)2, corresponding to four different phase transitions of which the one at -26C is reported here for the first time. Data on doped samples reveal the charge transport mechanism in the crystal.
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Anomalous variations of d.c. electrical conductivity with temperature are observed in ammonium sulphate single crystals, suggesting a possible phase transition at 150C. Measurements of thermally stimulated current also support these results. The mechanism of electrical conduction is explained on the basis of studies made on doped and quenched crystals.
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A new layered ammonium manganese(II) diphosphate, (NH4)(2)[Mn-3(P2O7)(2)(H2O)(2)], has been synthesised under solvothermal conditions at 433 K in ethylene glycol and the structure determined at 293 K using single-crystal X-ray diffraction data (M-r = 584.82, monoclinic, space group P2(1)/a, a = 9.4610( 8), b = 8.3565( 7), c = 9.477(1) Angstrom, beta = 99.908(9) degrees, V = 738.07 Angstrom(3), Z = 2, R = 0.0351 and R-w = 0.0411 for 1262 observed data (I > 3(sigma(I))). The structure consists of chains of cis- and trans-edge sharing MnO6 octahedra linked via P2O7 units to form layers of formula [Mn3P4O14(H2O)(2)](2-) in the ab plane. Ammonium ions lie between the manganese-diphosphate layers. A network of interlayer and ammonium-layer based hydrogen bonding holds the structure together. Magnetic measurements indicate Curie - Weiss behaviour above 30 K with mu(eff) = 5.74(1) mu(B) and theta = -23(1) K, consistent with the presence of high-spin Mn2+ ions and antiferromagnetic interactions. However, the magnetic data reveal a spontaneous magnetisation at 5 K, indicating a canting of Mn2+ moments in the antiferromagnetic ground state. On heating (NH4)(2)[Mn-3(P2O7)(2)(H2O)(2)] in water at 433 K under hydrothermal conditions, Mn-5(HPO4)(2)(PO4)(2).4H(2)O, synthetic hureaulite, is formed.
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The solvothermal synthesis and characterization of two indium selenides with stoichiometry [NH4][InSe2] is described. Yellow [NH4][InSe2] (1), which exhibits a layered structure, was initially prepared in an aqueous solution of trans-1,4-diaminocyclohexane, and subsequently using a concentrated ammonia solution. A red polymorph of one-dimensional character, [NH4][InSe2] (2), was obtained using 3,5-dimethylpyridine as solvent. [NH4][InSe2] (1) crystallizes in the non-centrosymmetric space group Cc (a=11.5147(6), b=11.3242(6), c=15.9969(9) and =100.354(3)). The structural motif of the layers is the In4Se10 adamantane unit, composed of four corner-linked InSe4 tetrahedra. These units are linked by their corners, forming [InSe2] layers which are stacked back to back along the c-direction, and interspaced by [NH4]+cations. The one-dimensional polymorph, (2), crystallizes in the tetragonal space group, I4/mcm (a=8.2519(16), c=6.9059 (14) ). This structure contains infinite chains of edge-sharing InSe4 tetrahedra separated by [NH4]+ cations.
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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 μmol.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 μmol.L-1), NO3- (0,17 0,25μmol.L-1) e PO4-2 (0,41 0,13μmol.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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We report on electrical relaxation measurements of (1-x)NH4H2PO4-xTiO(2) (x = 0.1) composites by admittance spectroscopy, in the 40-Hz-5-MHz frequency range and at temperatures between 303 and 563 K. Simultaneous thermal and electrical measurements on the composites identify a stable crystalline phase between 373 and 463 K. The real part of the conductivity, sigma', shows a power-law frequency dependence below 523 K, which is well described by Jonscher's expression sigma' = sigma(0)(1 + (omega/omega(p))(n)), where sigma(0) is the dc conductivity, omega(p)/2 pi = f(p) is a characteristic relaxation frequency, and n is a fractional exponent between 0 and 1. Both sigma(0) and f(p) are thermally activated with nearly the same activation energy in the II region, indicating that the dispersive conductivity originates from the migration of protons. However, activation energies decrease from 0.55 to 0.35 eV and n increases toward 1.0, as the concentration of TiO2 nanoparticles increases, thus, enhancing cooperative correlation among moving ions. The highest dc conductivity is obtained for the composite x = 0.05 concentration, with values above room temperature about three orders of magnitude higher than that of crystalline NH4H2PO4 (ADP), reaching values on the order of 0.1 (Omega cm)(-1) above 543 K.
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Welsch (Projektbearbeiter): Anfrage an den Banus von Kroatien Jellai nach der Einschlieung Wiens und der Entwaffnung der Nationalgarden der Umgebung, ob er gewillt sei, a) seine Truppen aus der Umgebung Wiens abzuziehen, um somit der Stadt auerordentliche Verteidigungsmanahmen zu ersparen, b) jeden feindseligen Akt gegen die Bevlkerung sofort einzustellen und c) sich vllig aus sterreich und Ungarn nach Kroatien zurckzuziehen
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Welsch (Projektbearbeiter): Der Anla der Einschlieung Wiens ist der bewaffnete Angriff von Teilen der Wiener Bevlkerung sowie der Nationalgarde auf das Militr. Die Truppen (Auerspergs) haben sich daraufhin zurckgezogen und eine "nicht die Stadt bedrohende ... Aufstellung" genommen. Da nach der Plnderung des unter der Obhut der Nationalgarde stehenden Zeughauses und der allgemeinen Volksbewaffnung keine vertrauenswrdige Autoritt in der Stadt mehr ersichtlich ist und auch ein verantwortliches Ministerium nur noch dem Namen nach existiert, harrt das Militr nun kaiserlicher Befehle
