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[en] Atomic-molecular mechanisms of crystal growth can be modeled based on crystallochemical information using cellular automata (a particular case of finite deterministic automata). In particular, the formation of heteropolyhedral layered complexes in uranyl selenates can be modeled applying a one-dimensional three-colored cellular automaton. The use of the theory of calculations (in particular, the theory of automata) in crystallography allows one to interpret crystal growth as a computational process (the realization of an algorithm or program with a finite number of steps).
[en] Se can regulate Cd accumulation and translocation in plants; however, such effects can be controversial because of the differences in plant species and Se species. In this study, pak choi was cultured under hydroponic conditions, and the effects of selenite and selenate on Cd accumulation were investigated in the edible parts of this vegetable. The results showed gradual improvements in the effects of the two Se species on the Cd content in pak choi shoots at the four assessed growing stages. Selenite did not lead to significant changes in Cd accumulation in the shoots until day 40, when it significantly reduced the accumulation by 34%. Selenate was always found to increase the Cd content in the shoots, and the differences on days 19 and 40 were 16% and 45%, respectively, compared with those of the Cd (only) treatment. Accordingly, selenate invariably enhanced Cd translocation from the roots to the shoots, whereas selenite insignificantly reduced the translocation only on day 40. Generally, selenomethionine (SeMet) accounted for much larger proportions in selenite-treated plants, while SeO42− was the dominant Se species in selenate-treated plants. However, under both Se treatments, the SeMet proportion increased substantially from day 19 to day 40 when that of SeO42− exhibited a drastic decrease; therefore, the relative proportion of seleno-amino acids to SeO42− may be the key factor for the regulation of Cd accumulation in pak choi via treatment with selenite and selenate at the different growing stages.
[en] The monoclinic room-temperature structure of tricaesium hydrogen bis[tetraoxoselenate(2-)] was refined from high-resolution neutron powder diffraction data. Special emphasis was given to the precise location of the H atom and the determination of the hydrogen-bond network. A Fourier analysis clearly shows that the H atom is distributed over two symmetry-equivalent positions of half occupancy [H..H = 0.52 (2) A] around an inversion centre. The hydrogen bridge is non-linear [O-H..O = 173 (2) ] with an O..O distance of 2.506 (7) A. (orig.)
[en] Obtained and discussed are infrared absorption spectra (400-4000 cm-1) of the following indium selenates: In2(SeO4)3x5H2O, In2(SeO4)3x9H2O, NaIn(SeO4)2x6H2O, NaIn(SeO4)2xH2O, MIn(SeO4)2x4H2O (M=NH4, K, Rb), CsIn(SeO4)2x2H2O, Na3In(SeO4)3x7H2O, MIn(SeO4)2 (M=NH4, Na, K, Rb, Cs), M2InOH(SeO4)2xyH2O (M=NH4, Na, K, Rb) and K2InOD(SeO4)2xyD2O
[en] Complexation in the system K2SeO4-UO2SeO4-H2O at 25 degrees C is studied by isothermal solubility. Congruently soluble K2UO2(SeO4)2·4H2O (I) and incongruently soluble K2(UO2)2(SeO4)3·6H2O (II) are observed. The unit-cell constants of I and II are determined from an X-ray diffraction investigation. For I, a = 12,969, b = 11.588, c = 8.533 angstrom, Z = 4, space group Pmmb. For II, a = 23.36, b = 6.784, c = 13.699 angstrom, β = 104.42 degrees, Z = 4, space group P2/m, P2, or Pm. Complexes I and II are representatives of the crystal-chemical groups AB22M1 and A2T33M1, respectively, of uranyl complexes
[en] Some precipitation titrations have been evaluated for the determination of the oxo anions of selenium and tellurium. Selenite and tellurite can be titrated with sodium diethyldithiocarbamate, using a silver ion-selective electrode as sensor. Tellurite can be titrated with cetylpyridinium chloride, using a poly(vinylchloride)/dioctylphthalate-coated graphite rod as sensor. Silver nitrate can be used to titrate selenite, tellurite, and tellurate. While the sum of tellurite and tellurate can be estimated, no sequential titration is possible. Lead nitrate can be used for the titration of selenite in the presence of selenate, in aqueous solution. In 80% methanolic solution the sum of selenite and selenate is titrated with lead nitrate. (Author)