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81.
Emulsion liquid membranes (ELM) with di-2-ethylhexylphosphoric acid in n-alkane, and dipicrylamine and cobalt(III) dicarbollide in nitrobenzene stabilized in double emulsions by SPAN 80/85 surfactant were used for preconcentration of radioactive fission products (137Cs,90Sr,139Ce, and152Eu) from slightly acidic nitrate solutions. The efficiency of sulfuric, phosphotungstic and silicotungstic acids as stripping agents, and picric acid as the bulky anion additive was investigated. A group separation of the fission products is possible by the ELM technique and can be considered for their removal from waste water solutions. 相似文献
82.
van Hooft PA El Oualid F Overkleeft HS van der Marel GA van Boom JH Leeuwenburgh MA 《Organic & biomolecular chemistry》2004,2(9):1395-1403
The scope of a stereoselective three-step approach for the synthesis of sugar derived spiroketals is presented. The methodology consists of Grignard addition of vinyl- or allylmagnesium bromide to a carbohydrate lactone, followed by K-10 clay mediated glycosidation with a terminal alkenol and subsequent ring-closing metathesis of the resulting diene. The generality of this procedure is demonstrated by the synthesis of various pyranose- and furanose-derived spiroketals, as well as more advanced tricyclic spiroketal derivatives. It is shown that functionalisation of the double bond in the resulting spiroketals leads to fused polycyclic ethers. 相似文献
83.
Nitrile butadiene rubber, NBR, structural foam of different apparent densities was obtained by using different concentrations of foaming agent, azodicarbonamide, ADC/K. The true stress-strain characteristics, in case of compression, of foamed samples after the application of cyclic stress-strain were measured. The effect of the cyclic stress-strain on strain energy density of ADC/K foaming agent-filled NBR rubber composites was studied. The mechanical parameters were found to depend on the foaming agent concentration and on the pre-cyclic fatigue number. Results also indicated that the strain energy decreased with filler concentration.The effects of the cyclic stress-strain on the conductivity of ADC/K foaming agent-filled NBR rubber composites were studied. The electrical properties were found to depend on the foaming agent concentration, the strain amplitude and the number of stress-strain cycles of pre-strain. This study was assisted by the current-voltage characteristics which were measured under the effect of different compression ratios: 0%, 5%, 10%, 15%, 20%, 25% and 30%. The free current carrier mobility and the equilibrium concentration of charge carriers in the conduction band were produced as functions of compressive strain. Results also indicate that there is a linear variation between pressure and conductivity for all samples, which means that these samples can be used as a pressure sensor. 相似文献
84.
Haggag Awad Abd El Mageed K. F. El Sahhar Kenneth R. Robertson Ramin Parham Constantin A. Rebeiz 《Photochemistry and photobiology》1997,66(1):89-96
Abstract— On the basis of the steady-state accumulation of divinyl (DV) or monovinyl (MV) protochlorophyllide (Pchlide) a in darkness (D) or in the light (L), green plants have been classified into three different greening groups namely dark divinyl-light divinyl (DDV-LDV), dark monovinyl-light divinyl (DMV-LDV) and dark monovinyl-light monovinyl (DMV-LMV) (Ionannides et al., Biochem. Syst. Ecol. 22, 211-220,1994). Interruption of the L phase of the photoperiod by a brief period of darkness (LD condition) revealed a predominance of different chlorophyll (Chl) a biosynthetic routes, depending upon the greening group affiliation of the plant species. For example, in DMV-LDV and DMV-LMV plants, the predominant Chl a biosynthetic routes under the LD condition appear to be the MV Chi a biosynthetic route and/or a mixed DV-MV Chi a biosynthetic route that bifurcates at the level of DV Pchlide a. On the basis of DV and MV Pchlide a accumulation rates after re-darkening, this greening group is designated as a light-dark MV (LDMV) subgroup. In DDV-LDV plants, the predominant LD Chi a biosynthetic routes appear to be the DV Chi a biosynthetic route and/or a mixed DV-MV Chi a biosynthetic route that bifurcates at the level of DV Chlide a. This greening group is designated as a light-dark DV (LDDV) subgroup. It is proposed that upon inhibiting the conversion of Pchlide a to Chi a by interruption of the L phase of the photoperiod by a brief period of D, the rates of DV and MV Pchlide a regeneration may reflect the carryover rates of DV and MV Pchlide a biosynthesis in L instead of reflecting a differential use of DV and MV carboxylic biosynthetic rates in D. It is also shown that in LDMV plants, MV Chlide a and MV Chi a are formed without the participation of [4-vinyl] Chlide a reductase. On the basis of recently published evidence, it is also argued that Pchlide oxidoreductase-A (POR-A) may be active in LDDV plants, while POR-B may predominate in LDMV plant species. The evolutionary significance of the LDDV and LDMV greening subgroups is discussed. 相似文献
85.
Jacques Barrau Ghassoub Rima Tajani El Amraoui 《Journal of organometallic chemistry》1998,570(2):8645
The reactions of the divalent species (ArO)2M (Ar=2,4,6-[(CH3)2NCH2]3C6H2; M=Ge, Sn) with either Me3SiN3, elemental S8, Se or transition metal complexes M′(CO)n+1 (M′=Fe, n=4; M′=Cr, W; n=5) (Ph3P)2Pt·C2H4 have resulted in the isolation of either the new stable formal metallanimines (ArO)2M=N–SiMe3, germanethione, -selone (ArO)2Ge=E (E=S, Se) (the expected formations of the stannanethione and -selone were not observed), or the (ArO)2M=M′(CO)n, (ArO)2M=Pt(PPh3)2 complexes, respectively. The direct oxidation of the (ArO)2M species with various oxidizing agents led to the formation of the corresponding metalloxanes [(ArO)2M–O–]2. All of the chalcogenido- and transition metal–metal 14 complexes have been physicochemically and chemically characterized. The reactions of the (ArO)2Ge=E (E=S, Se) compounds with 3,5-di-tert-butyl-1,2-benzoquinone produced, by extrusion of sulfur or selenium, the dioxametalloles corresponding to the formal addition of the divalent species (ArO)2M to the benzoquinone. A substitution reaction of chalcogen (S/Se) has been observed permitting to go from germaneselone to germanethione. 相似文献
86.
Abdelkrim El‐Ghayoury Albertus P. H. J. Schenning E. W. Meijer 《Journal of polymer science. Part A, Polymer chemistry》2002,40(22):4020-4023
An oligo(p‐phenylene vinylene) that contains terpyridine ligands has been synthesized. Upon addition of metal ions, a π‐conjugated metallo polymer is formed in which the well‐defined character of oligomers and the material properties of polymers are combined. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4020–4023, 2002 相似文献
87.
88.
1-Phenyl-2-(benzenesulphonyl)-ethylene and 1-phenyl-2-(benzenesulphonyl)-prop-1-ene have been shown to undergo ,-photoisomerisation, whereas 2-benzenesulphonylindene readily forms [π2 + π2] photoadducts with 2,3-dimethylbut-2-ene, cyclopentene, and cyclohexene. 相似文献
89.
Magdalena Kurdziel Elżbieta Szczepaniec-Cieciak Monika Watorczyk Barbara Dabrowska 《Journal of solution chemistry》2004,33(5):453-464
The solubility of solid 2-methyl-1,3-butadiene (isoprene) in liquid argon at a temperature of 87.3 K and in liquid nitrogen at 77.4 K has been measured by the filtration method. The hydrocarbon contents in solutions were determined using gas chromatography. GC–MS was used to identify impurities in the solute. The experimental value of the mole fraction solubility of solid isoprene in liquid argon at 87.3 K is (1.41 ± 0.27) × 10–6 and (1.56 ± 0.36) × 10–7 in liquid nitrogen at 77.4 K. The Preston–Prausnitz method was used for calculation of the solubilities of solid hydrocarbon in liquid argon in the temperature range 84.0–110.0 K and in liquid nitrogen from 64.0 to 90.0 K. The solvent–solute interaction parameters l
12 were also calculated. At 90.0 K liquid argon is a better solvent for isoprene than is liquid nitrogen. The experimental values of the solubilities of isoprene in liquid argon and nitrogen were compared with results obtained for selected unsaturated and aromatic hydrocarbons. 相似文献
90.
The thermodynamic properties of the mixed aqueous electrolyte of ammonium and alkaline earth metal nitrates have been studied using the hygrometric method at 25?°C. The water activities of these {yNH4NO3+(1?y)Y(NO3)2}(aq) systems with Y ≡ Ba2+, Mg2+ and Ca2+ were measured at total molalities ranging from 0.10 mol?kg?1 to saturation for different NH4NO3 ionic-strength fractions of y=0.20, 0.50 and 0.80. These data allow the calculation of osmotic coefficients. From these measurements, the ionic mixing parameters are determined and used to calculate the solute activity coefficients in the mixtures at different ionic-strength fractions. The results of these ternary solution measurements are compared with those for binary solutions of the alkaline earth nitrates of magnesium, calcium and barium with ammonium nitrates. The behavior of the aqueous electrolyte solutions containing mixtures of barium or calcium or magnesium with ammonium nitrates are correlated and show that ionic interactions are more important for the system containing Mg2+ than for Ca2+ or Ba2+. The trends are mainly due to the effects of the ionic size, polarizability and the hydration of the ions in these solutions. 相似文献