New melamine–formaldehyde–ketone polymers. IV. Dissolution of melamine in reactive solvents prepared from methyl ethyl ketone

Reactive solvents of melamine were prepared from methyl ethyl ketone and formaldehyde in the presence of the catalyst triethylamine. The solubility of melamine in the resulting solvents was determined, and the mechanism of dissolution was explained with ¹H‐NMR and IR spectroscopy. Preliminary experiments aimed at curing the melamine solutions in reactive solvents into melamine–formaldehyde–butanone resins are reported. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1496–1505, 2006     

Polyacrylate anion exchangers in sorption of heavy metal ions with the biodegradable complexing agent

The removal of Co(II) and Ni(II) from aqueous solutions in the presence of complexing agent on the polyacrylate anion exchangers with different basicity of functional groups Amberlite IRA 458, Amberlite IRA 958 and Amberlite IRA 67 was described. The complexing agent Baypure CX 100 is a new generation of chelators, undergoing biodegradation. It constitutes an alternative for the reagents of EDTA or NTA type. The studies were carried out by the static (batch) and the dynamic (column) methods. The influence of several parameters such as ratio of M(II)–L, pH, temperature were studied with respect to sorption equilibrium. Sorption isotherms were obtained and fitted using the Langmuir and Freundlich models. Kinetic curves were fitted using the pseudo first-order, the pseudo second-order as well as the intraparticle diffusion model equations to evaluate most effective one. Physicochemical properties of anion exchangers such as their structure, basicity of functional groups were also taken into account. Additionally, the obtained results were compared with those for the weakly acidic cation exchanger Purolite C-104.     

Application of monodispersive anion exchangers in sorption and separation of Y^3＋ from Nd^3＋ and Sm^3＋ complexes with dcta

Rare earth complexes with trans-1,2-diaminocyclohexane-N,N,N ,N -tetraacetic acid （DCTA） of the Ln（dcta） type exhibited an unusual sequence of affinity on the polystyrene anion exchangers： pm^3＋〉Nd^3＋〉Sm^3＋〉Pr^3＋〉Ce^3＋〉Eu^3＋〉Gd^3＋〉La^3＋〉Sc^3＋〉Tb^3＋〉Dy^3＋〉 Ho^3＋〉Y^3＋〉Er^3＋〉Tm^3＋〉Yb3＋〉Lu^3＋[1]. Taking into account the position of Y^3＋, Sm^3＋, and Nd^3＋ in this affinity series, for the monodispersive polystyrene anion exchangers, Lewatit MonoPlus M 500, Lewatit MonoPlus M 600, Lewatit MonoPlus MP 500, Lewatit MonoPlus MP 64, and for the heterodispersive anion exchanger, Lewatit MP 62, the weight （Dg） and bed （Dv） distribution coefficients of these complexes and working ion exchange capacities （Cw） were determined. Based on these values, purifications of Y^3＋ from Nd^3＋ and Y^3＋ from Sm^3＋ in the macro-micro component system on these anion exchangers were studied. The application potential of this method was highlighted for the separation of Y^3＋ in the presence of Nd^3＋ and Sm^3＋. With 1 L of monodispersive and strongly basic polystyrene gel anion exchanger Lewatit MonoPlus M 500 in the acetate form, it is possible to obtain approximately 79 g Y2O3 purified from Nd2O3 and 70 g Y2O3 purified from Sm2O3 in the same process condition.     

Adsorption of 1,1,3,3-tetramethyl-2-thiourea on the mercury electrode: dependence on the concentration of the base electrolyte

Adsorption of 1,1,3,3-tetramethyl-2-thiourea (TMTU) on a mercury electrode from 1, 0.5, and 0.1 M NaClO₄ is described by means of the adsorption isotherms constants calculated from the surface pressure as a function of electrode charge density and adsorbate bulk concentration. The adsorption parameters for the double-layer were calculated based on the data from the differential capacity-potential curves. The values of the relative surface excess increase with an increase in the concentration of NaClO₄. In each system studied, significantly smaller values of Γ_S for σ_M<0 were obtained, compared with the corresponding values for σ_M≥0. At positive values of σ_M, the values of ΔG° obtained from either the Frumkin or the Flory-Huggins isotherm are similar. However, the values of the parameter A obtained from the Flory-Huggins isotherm are lower.The dependence of Φ^M−2 on the relative surface excess at a constant charge density is nonlinear. The rectilinear segments of these dependences obtained for smaller values of Γ′ were analyzed in order to calculate the electrostatic parameters of the inner layer.     

Polyetherols from melamine and alkylene carbonates: Properties and application of foamed polyurethanes

Some results are presented on the applications of polyetherols obtained in reactions of melamine with alkylene carbonates for preparation of foamed polyurethanes. Physical properties of the polyetherols and the parameters of their use are evaluated. Selected properties of polyurethane foams obtained by using the polyetherols, such as apparent density, uptake volume, linear shrinkage, and flammability, are presented. Thermal properties of the products have been found to be much better than those of traditional polyurethane foams. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2302–2308, 2004     

On Divergence-Power Inequalities

Expressions for (entropy-power inequality (EPI) Shannon type) divergence-power inequalities (DPIs) in two cases (time-discrete and time-continuous) of stationary random processes are given. The new expressions connect the divergence rate of the sum of independent processes, the individual divergence rate of each process, and their power spectral densities. All divergences are between a process and a Gaussian process with same second-order statistics, and are assumed to be finite. A new proof of the Shannon EPI, based on the relationship between divergence and causal minimum mean-square error (CMMSE) in Gaussian channels with large signal-to-noise ratio, is also shown     

Determination of Anionic Surfactants by Means of Photometric Titration with Methylene Blue Dye

Quantitative determination of dodecyl sulfate and dioctyl sulfosuccinate has been performed with methylene blue dye in titration mode. The new approach consists in the titration of surfactant solution by standardized dye solution, simultaneously measuring absorbance at 660 nm with an immersion probe. Due to the formation of sparingly soluble ion pairs, the registered photometric titration curves are dependent on surfactant concentration. The analytical signal is the titrant volume needed to reach a certain absorbance value. The main advantage of the proposed method is that no toxic organic solvent is used. An additional advantage is that the analysis procedure can be carried out using an automatic titrator. The determination range is dependent on the end‐point absorbance value. Standard deviation values fall in the range from 2 to 7 %. The method may be useful for routine process control in the surfactant industry.     

Antennal and mouthpart sensilla of Acanthoscelides obtectus say (Coleoptera: Bruchidae)

Acanthoscelides obtectus, a serious pest with a worldwide distribution, damages stored seeds of Phaseolus sp. To acquire a better understanding of the sensory orientation of bean weevils, their antennal and palpal sensilla were investigated. The antennae and palps possess several types of sensory hairs: blunt‐tipped sensilla chaetica and trichoidea and also sharp‐tipped sensilla trichoidea, these last being the most numerous. Sensilla basiconica are present only on the flagellomeres, but Böhm bristles occur on the basal sclerite and scape of the antennae. The terminal segments of the maxillary and labial palps bear a group of sensilla styloconica with single apical pores. Sensilla coeloconica are located only on the terminal palpal segments. They were unable to detect any distinct morphological differences between males and females. The possible chemosensory, mechanosensory, and thermo‐/hygroreceptive functions of the sensilla are discussed.     

Detector effects in photothermal deflection experiments

We report on the theoretical analysis of a detector type influence on the normal deflection signal in photothermal experiments. Two cases are examined. In the first, the quadrant photodiode was considered as the detector; in the second the signal from the position detector, which measures the central moment displacement of the probe beam, was analyzed. Both analyses were carried out within the framework of the complex ray theory. The normal photodeflection signal was found to depend on the type of detector used in the photothermal deflection experiments for some parameters of its setup.     

The changes in the contents of 137Cs in bottom sediments of some Masurian lakes during 10-15 y observation (Poland)

The measurements of radioactive caesium contents in bottom sedimentswere carried out in four lakes. First samples (47) were takenin 1992–95. The repeat sampling (109) was performed fromthe same places in 2005. We examined eight chosen areas in theselakes. In six of them, we observed statistically significantdifferences in the level of radioactive caesium. It indicatesthe permanent decrease in the level of ¹³⁷Cs. The mean annualdecrease in the level of radioactive caesium, taking into considerationthe radioactive decay, was from 4.2 to 7.8%. In two areas ofthe profundal zone, we did not observe statistically significantdifferences in the level of radioactive caesium (lakes Garbasand Rogale Wielkie). Taking into consideration the radioactivedecay of caesium, it means about the appearance of the processof accumulation of ¹³⁷Cs in these areas.