Observation of random-phase gap solitons in photonic lattices

We report what is to our knowledge the first experimental observation of gap random-phase lattice solitons: self-trapped spatially incoherent entities whose modal constituents lie within a photonic bandgap.     

Noise barriers with varying cross-section optimized by genetic algorithms

The efficiency of a noise barrier largely depends on its geometry. Besides the height of the barrier and its top element form, the cross-section of the barrier contributes to its performance as well. The Boundary Element Method is often used as the numerical tool for simulating the behavior of proposed barrier shapes, both in 2D and 3D spaces. This paper deals with the optimization of barrier cross-section, not only by taking into account its acoustical performance (sound insertion loss), but also considering the economic feasibility of using various materials and various shapes for building the barrier. Therefore, the economic feasibility coefficient is defined and used as a final numerical value for comparing the overall efficiency of barrier design. The optimization process is done by using a genetic algorithm. Five basic forms of barrier elements and five building materials were pre-defined and characterized for the optimization process. The number of candidate units in the starting population was varied in order to examine the influence of population size on the final results. Barrier performance was evaluated for a point sound source in a 3D simulation space, and both its total rating based on the economic feasibility coefficient and its acoustical performance itself were evaluated and compared to a reference concrete barrier of the same height.     

Activity-guided isolation of novel norwithanolides from depreasubtriflora with potential cancer chemopreventive activity

Activity-monitored fractionation of a CHCl(3)-soluble extract of Deprea subtriflora using a quinone reductase induction assay led to the purification of subtrifloralactones A-J (1-10), 10 novel C-18 norwithanolides based on a new C(27) skeleton. These compounds were characterized by spectroscopic and chemical studies, and single-crystal X-ray diffraction analysis was used to confirm the structures of 1 and 4. Compounds 1-10 were evaluated for their cancer chemopreventive activity in terms of their ability to induce quinone reductase activity with cultured murine hepatoma cells, and compounds 1 and 6 were found to be highly effective.     

Physical investigation of the colloidal iron-inulin complex

The iron-inulin complex, which could be applied as a parenteral hematinic agent, is studied by physical techniques. Electron microscopy shows that the complex contains very small particles that are approximately spherical and 10–30 nm in diameter. The examination reveals the presence of an electron-transparent sheath, probably consisting of linked inulin oligomers with M _w ∼ 3000 g mol⁻¹, around the electron-dense, ironcontaining core of the FeOOH particles. FTIR spectroscopy suggests the existence of stronger hydrogen bonds, which are formed in the complexes between FeOOH and oligosaccharides, compared to the hydrogen bond in the initial compounds. A gel filtration technique on a Sephadex column showed conclusively that a large proportion of combined inulin oligomers with M _w ∼ 1500 g mol⁻¹ as secondary fractions are present in complexes. These low-molecular-weight inulin fractions have a significant influence on the complex stability. The text was submitted by the authors in English.     

Use of enantioselective liquid chromatography for preparation of pure atenolol enantiomers

The study reported here shows a practicable preparation of pure atenolol enantiomers using enantioselective liquid chromatography. The successful separation of enantiomers of the final atenolol and the intermediate ester and the good peak shapes could not have been obtained without diethylamine as a component of the mobile phase. That makes difficult the recycling of the three-component mobile phase, an unavoidable step in simulated moving bed chromatography separation technology. The only suitable methodology for preparation of atenolol enantiomers proved to be synthesis from its N-benzyl-N-isopropyl precursor and the chiral stationary phase Chiralpak AD was found to be very convenient for preparative separation of these enantiomers. The enantiomeric purities and recovery of separated enantiomers of this N-benzyl-N-isopropyl precursor were very high, allowing high enantiomeric purities of the final products, ee's 99.3% for S- and 99.0% for R-atenolol. The chromatographic separation parameters, as well as solubility of racemate in the mobile phase, are good bases for the further examination of possible scale-up resolution of compound 6.     

Identification of photocatalytic degradation products of diazinon in TiO2 aqueous suspensions using GC/MS/MS and LC/MS with quadrupole time-of-flight mass spectrometry

The photocatalytic degradation of the organophosphorus insecticide diazinon in aqueous suspensions has been studied by using titanium dioxide as a photocatalyst. The degradation of the insecticide was a fast process and included the formation of several intermediates that were identified using GC/ion-trap mass spectrometry with EI or CI in positive and negative ionization mode and HPLC/electrospray-QqTOF mass spectrometry. Since primarily hydroxy derivatives were identified in these aqueous suspensions, the mechanism of degradation was probably based on hydroxyl radical attack. The initial oxidative pathways of the degradation of diazinon involved the substitution of sulfur by oxygen on the Pz.dbnd6;S bond, cleavage of the pyrimidine ester bond, and oxidation of the isopropyl group. Exact mass measurements of the derivatives allowed the elemental formula of the molecules to be determined confidently. Similarities to the metabolic pathways occurring in living organisms were observed.     

Application of artificial neural networks for gradient elution retention modelling in ion chromatography

Gradient elution in ion chromatography (IC) offers several advantages: total analysis time can be significantly reduced, overall resolution of a mixture can be increased, peak shape can be improved (less tailing) and effective sensitivity can be increased (because there is little variation in peak shape). More importantly, it provides the maximum resolution per time unit. The aim of this work was the development of a suitable artificial neural network (ANN) gradient elution retention model that can be used in a variety of applications for method development and retention modelling of inorganic anions in IC. Multilayer perceptron ANNs were used to model the retention behaviour of fluoride, chloride, nitrite, sulphate, bromide, nitrate and phosphate in relation to the starting time of gradient elution and the slope of the linear gradient elution curve. The advantage of the developed model is the application of an optimized two-phase training algorithm that enables the researcher to make use of the advantages of first- and second-order training algorithms in one training procedure. This results in better predictive ability, with less time required for the calculations. The number of hidden layer neurons and experimental data points used for the training set were optimized in terms of obtaining a precise and accurate retention model with respect to minimization of unnecessary experimentation and time needed for the calculation procedures. This study shows that developed, ANNs are the method of first choice for retention modelling of inorganic anions in IC.     

QSPR modeling: graph connectivity indices versus line graph connectivity indices

Five QSPR models of alkanes were reinvestigated. Properties considered were molecular surface-dependent properties (boiling points and gas chromatographic retention indices) and molecular volume-dependent properties (molar volumes and molar refractions). The vertex- and edge-connectivity indices were used as structural parameters. In each studied case we computed connectivity indices of alkane trees and alkane line graphs and searched for the optimum exponent. Models based on indices with an optimum exponent and on the standard value of the exponent were compared. Thus, for each property we generated six QSPR models (four for alkane trees and two for the corresponding line graphs). In all studied cases QSPR models based on connectivity indices with optimum exponents have better statistical characteristics than the models based on connectivity indices with the standard value of the exponent. The comparison between models based on vertex- and edge-connectivity indices gave in two cases (molar volumes and molar refractions) better models based on edge-connectivity indices and in three cases (boiling points for octanes and nonanes and gas chromatographic retention indices) better models based on vertex-connectivity indices. Thus, it appears that the edge-connectivity index is more appropriate to be used in the structure-molecular volume properties modeling and the vertex-connectivity index in the structure-molecular surface properties modeling. The use of line graphs did not improve the predictive power of the connectivity indices. Only in one case (boiling points of nonanes) a better model was obtained with the use of line graphs.     

Physico-chemical characterization of thermal decomposition course in zinc nitrate-copper nitrate hexahydrates

This study reports experimental investigations by non-isothermal TG/DSC analysis of Zn(NO₃)₂·4H₂O, Cu(NO₃)₂·4H₂O and their mixtures of known compositions in the temperature range 30–1200°C. Solid/liquid transitions in the sealed samples of the hexahydrate salts and their mixtures were also studied by DSC in the temperature range 0–60°C. The mixture with composition 0.85Zn(NO₃)₂·6H₂O+0.15Cu(NO₃)₂·6H₂O showed single melting peak at 29°C. This mixture was chosen for detailed studies. Melting temperature and heat of fusion of single salt hexahydrates and of the mixture were calculated from DSC endotherms. The different stages in the thermal decomposition processes have been established. The intermediate and the final solid products of the thermal decomposition were analyzed by XRD. The scheme and the decomposition temperature depended on the composition of the starting material. The final decomposition products were CuO (monoclinic), Cu₂O (cubic), ZnO (hexagonal) and their mixtures with the defined crystalline structures. Possible influence of the addition of CuCl₂·2H₂O into the mixture 0.85Zn(NO₃)₂·6H₂O+0.15Cu(NO₃)₂·6H₂O and a gel combustion technique of the precursor preparation, on the composition and morphology of the solid decomposition products, were also studied. The gel combustion technique, using citric acid added to a mixture of 0.85Zn(NO₃)₂·6H₂O+0.15Cu(NO₃)₂·6H₂O, was applied in an attempt to obtain mixed Zn/Cu oxides of a particular mole ratio. The morphology of the solid decomposition products was examined by SEM.