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991.
992.
Filip J Yngard RA Siskova K Marusak Z Ettler V Sajdl P Sharma VK Zboril R 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(36):10097-10105
The reaction of potassium ferrate(VI), K2FeO4, with weak‐acid dissociable cyanides—namely, K2[Zn(CN)4], K2[Cd(CN)4], K2[Ni(CN)4], and K3[Cu(CN)4]—results in the formation of iron(III) oxyhydroxide nanoparticles that differ in size, crystal structure, and surface area. During cyanide oxidation and the simultaneous reduction of iron(VI), zinc(II), copper(II), and cadmium(II), metallic ions are almost completely removed from solution due to their coprecipitation with the iron(III) oxyhydroxides including 2‐line ferrihydrite, 7‐line ferrihydrite, and/or goethite. Based on the results of XRD, Mössbauer and IR spectroscopies, as well as TEM, X‐ray photoelectron emission spectroscopy, and Brunauer–Emmett–Teller measurements, we suggest three scavenging mechanisms for the removal of metals including their incorporation into the ferrihydrite crystal structure, the formation of a separate phase, and their adsorption onto the precipitate surface. Zn and Cu are preferentially and almost completely incorporated into the crystal structure of the iron(III) oxyhydroxides; the formation of the Cd‐bearing, X‐ray amorphous phase, together with Cd carbonate is the principal mechanism of Cd removal. Interestingly, Ni remains predominantly in solution due to the key role of nickel(II) carbonate, which exhibits a solubility product constant several orders of magnitude higher than the carbonates of the other metals. Traces of Ni, identified in the iron(III) precipitate, are exclusively adsorbed onto the large surface area of nanoparticles. We discuss the relationship between the crystal structure of iron(III) oxyhydroxides and the mechanism of metal removal, as well as the linear relationship observed between the rate constant and the surface area of precipitates. 相似文献
993.
L Ohnoutkova O Zitka K Mrizova J Vaskova P Galuszka N Cernei MA Smedley WA Harwood V Adam R Kizek 《Electrophoresis》2012,33(15):2365-2373
Nutritional quality of human and animal foodstuffs is determined by the content of essential amino acids. Barley is the fourth most important cereal of the world and the second most important cereal grown in the Czech Republic. Cereal grains such as barley contain insufficient levels of some essential amino acids, especially lysine. Dihydrodipicolinate synthase is the key enzyme involved in the regulatory step for lysine biosynthesis. Two constructs pBract214::sTPdapA and pBract214::mdapA containing the dapA gene from Escherichia coli coding for the bacterial dihydrodipicolinate synthase were used for transformation of barley. An Agrobacterium-mediated technique was used for transformation of immature embryos of spring barley cv. Golden Promise. Transgenic barley plants of the T0 and T1 generations were evaluated by PCR, real-time PCR, gel electrophoresis, and Western blot. Amino acid content was analyzed by HPLC after HCl hydrolysis. The lysine content in leaves of the T1 generation plant no. 5/5 was 50% higher than in wild-type plants; the lysine content in seeds of T2 generation plant no. 5/16 was 30% higher than in wild-type seeds of spring barley cv. Golden Promise. 相似文献
994.
Miroslava ?pérová Petr Nasadil Alena Pr??ová Ji?í Ku?erík 《Journal of Thermal Analysis and Calorimetry》2012,110(1):71-76
The degree of polymerization is one of the main parameters reflecting cellulose ageing. Viscometry is a method frequently used for determination of cellulose fibers polymerization degree, however, sample preparation and viscosity measurement are demanding, time consuming and do not provide reproducible results. In this study, the relationship between polymerization degree of cellulose fibers obtained by viscosity measurement and their degradation parameters obtained by thermal analysis were investigated. Differential scanning calorimetry provided values of effective combustion heat and thermogravimetry (TG) was used for the determination of temperatures and associated mass losses during the cellulose degradation. Effective combustion heat did not show any correlation with degree of polymerization of investigated cotton fabrics. In contrast, results from TG suggested several promising nonlinear correlations which could be used as a hint to develop a method useful for quick determination of cotton fabrics polymerization degree. The most promising correlations with cellulose polymerization degree were found for both rates of thermal and thermo-oxidative degradations. 相似文献
995.
Mirjana Metikoš-Huković Jozefina Katić Ingrid Milošev 《Journal of Solid State Electrochemistry》2012,16(7):2503-2513
Anodic polarization of nitinol in acetic acid under galvanostatic conditions produces oxide films composed mainly of TiO2. An exponential current-field relation is valid during ionic conduction through the growing oxide, in which the field coefficient is related to the jump distance. Transport processes in anodic films have been discussed in terms of a cooperative mechanism developed for amorphous oxide films on valve metals, in which both metal and oxygen ions were involved in ionic conduction. For more crystalline oxide structure of passive films on nitinol, formed during a prolonged potentiostatic conditions, the charge transfer takes place only through the oxygen vacancies as mobile species via a high-field-assisted mechanism. Based on the results of the Mott–Schottky analysis, these films behave as n-type semiconductors indicating that oxygen vacancies formed during the film formation and growth act as electron donors. The barrier/protecting and electronic/semiconducting properties of the passive films as well as their chemical composition were studied using electrochemical impedance spectroscopy and X-ray photoelectron spectroscopy. 相似文献
996.
Novák P Lishchynskyi A Grushin VV 《Angewandte Chemie (International ed. in English)》2012,51(31):7767-7770
Easy does it: Aryl boronic acids undergo smooth and selective trifluoromethylation with low-cost fluoroform-derived CuCF(3) in DMF in non-dried air. The reaction occurs under mild conditions (1?atm, room temperature), exhibits unprecedented functional-group tolerance, and affords trifluoromethylated aromatic compounds in up to 99?% yield. 相似文献
997.
Nachtigall P Grajciar L Pérez-Pariente J Pinar AB Zukal A Čejka J 《Physical chemistry chemical physics : PCCP》2012,14(3):1117-1120
Proper combination of template and optimized reaction conditions provides zeolite FER with homogeneous distribution of Al in the framework; this results in a new zeolite adsorbent exhibiting a constant heat of CO(2) adsorption. 相似文献
998.
Dimitrić Marković JM Marković ZS Pašti IA Brdarić TP Popović-Bijelić A Mojović M 《Dalton transactions (Cambridge, England : 2003)》2012,41(24):7295-7303
Combined spectroscopic (UV/visible, MS and EPR), electrochemical (CV) and theoretical approaches were used to evaluate the relevant interactions of morin and quercetin, as well as their respective iron(III) complexes with DPPH, tempone, hydroxyl and superoxide radicals. The results on iron complexation specify the stoichiometry and the relevant structural forms entering the chelation of the molecules. The spectroscopic DPPH assay shows better antioxidant activity of quercetin and its iron complex both in terms of EC(50) values and stoichiometry. The results of 2-deoxyribose degradation suggest that antioxidant activities of morin and quercetin may originate from their combined effect of iron chelation and radical scavenging. The distinctive difference in the EPR spectra of morin and quercetin radicals suggests different positions of the radical centers which may account for different sequences of their activities towards investigated radicals. Activity ranking of quercetin and morin, established by cyclic voltammetry, confirms their activity sequence obtained by EPR results and is also in agreement with the results of conformational analysis. The equilibrium geometries, optimized with the M052X functionals and 6-311G(d,p) basis set, predict structural modifications between the ligand molecules in the free state and in the complex structures. The arguments gained through experimental results can also be rationalized in terms of overall molecular geometry and structural features governing antioxidant behavior i.e. substitution pattern of the ring B. 相似文献
999.
Šimon P Jambor R Růžička A Lyčka A De Proft F Dostál L 《Dalton transactions (Cambridge, England : 2003)》2012,41(17):5140-5143
NCN chelated monomeric chalcogenides, LSbE (E = S (1), Se (2), L = 2,6-bis[N-(2',6'-dimethylphenyl)ketimino]phenyl), were synthesized and characterized with the help of elemental analysis, NMR spectroscopy and single-crystal X-ray diffraction analyses. The terminal Sb-E (E = S, Se) bonds in 1 and 2 were subjected to theoretical investigation and the results are compared with the hypothetical molecules, PhSb=E (E = S, Se, Te), and earlier reported analogues. 相似文献
1000.
Glasses in the ternary ZnO-P2O5-TeO2 system were prepared and studied in two compositional series (100 − x)[0.5ZnO-0.5P2O5]-xTeO2 (X-series) and 50ZnO-(50 − y)P2O5-yTeO2 (Y-series) within the concentration range of x = 0-60 and y = 0-40 mol% TeO2. Their structure was studied by Raman and 31P MAS NMR spectroscopies. The incorporation of TeOx units into the structural network is associated with the depolymerisation of phosphate chain structure as revealed by both methods. At a high TeO2 content isolated PO4 tetrahedra are formed in the structure of glass series Y, while diphosphate O3P-O-PO3 groups are present in the structure of the glass series X. In the structure of glass series Y tellurium atoms form predominantly TeO3 trigonal pyramids, whereas in the X glass series TeO4 trigonal bipyramids prevail in the glass structure. The addition of TeO2 to the parent zinc metaphosphate glass results in a decrease of glass transition temperature in both compositional series associated with the replacement of stronger P―O bonds by weaker Te―O bonds. 相似文献