Chemical and technological characterization of medieval glass bracelets from South-East Bulgaria

The present paper deals with chemical and physicochemical characterization of seven glass fragments of medieval glass bracelets from South-East Bulgaria. Samples were investigated by Fourier-transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM) and differential thermal analysis (DTA). Gravimetric chemical analysis was used for silica assessment. Flame photometry was applied to determine sodium and potassium content while aluminium, calcium and magnesium were determined by flame atomic absorption spectrometry after dissolution using a mixture of acids. All investigated artefacts are soda-lime-silica glasses and when produced two different recipe norms were used. Important technological parameters of glass manufacturing were determined and discussed. This investigation throws light on the technological development and production of glass during medieval times.      

Extension of the ladder model of self-assembly from cylindrical to disclike surfactant micelles

The ladder model of growth of cylindrical micelles gives expressions for the micellar size distribution and for the mean aggregation number, which are in good agreement with the experiment. Here, we consider this model and its extension to the case of disclike micelles. In analogy with the modeling of elongated micelles as sphero-cylinders, the disclike micelles can be modeled as toro-discs. Upon micelle growth, the hemispherical caps of a cylindrical aggregate remain unchanged, whereas the semitoroidal periphery of a disclike micelle expands. This effect can be taken into account in the expression for the size distribution of the disclike micelles, which predicts the dependence of the micelle mean aggregation number on the surfactant concentration. It turns out that disclike micelles could form in a limited range of surfactant concentrations, and that their mean aggregation number cannot exceed a certain maximal value. Large disclike micelles can exist only near the border with the domain of cylindrical micelles. Then, small variations in the experimental conditions could induce a transformation of the disclike micelles into cylindrical ones.     

low-frequency dispersion of surface conducting particles as measured by means of electrorotation

Electrorotation of glutaraldehyde-fixed red blood cells (RBCs) has been investigated in the frequency range from 16 Hz to 30 MHz. Special emphasis has been given to the low-frequency range (16 Hz–2 kHz). In this region, a distinctly new type of co-field rotation peak was observed. Native RBCs also show low-frequency rotation, but much less pronounced. The low-frequency rotation is nonmonotonous with regard to conductivity. With increasing external conductivity, the low-frequency rotation speed reaches a maximum of around 3.5 mS/m and decreases again when the external conductivity is increased further. The low-frequency co-field rotation peak was observed between 30 Hz and 70 Hz except at very low conductivity almost independent of electrolyte concentration. Decreasing surface charge density by means of neuraminidase led to a reduction of the rotation speed in the low-frequency range. The position of the peak remained unaffected by changes of the surface charge density. These experimental results are not consistent with the typical Pauli–Schwan- and Maxwell–Wagner-dispersion. They rather suggest the presence of a concentration polarization mechanism responsible for the low-frequency electrorotation peak.     

Molecular structure and spectroscopic studies on novel complexes of coumarin-3-carboxylic acid with Ni(II), Co(II), Zn(II) and Mn(II) ions based on density functional theory

Novel Ni(II), Co(II), Zn(II) and Mn(II) complexes of coumarin-3-carboxylic acid (HCCA) were studied at experimental and theoretical levels. The complexes were characterised by elemental analyses, FT-IR, (1)H NMR, (13)C NMR and UV-Vis spectroscopy and by magnetic susceptibility measurements. The binding modes of the ligand and the spin states of the metal complexes were established by means of molecular modelling of the complexes studied and calculation of their IR, NMR and absorption spectra at DFT(TDDFT)/B3LYP level. The experimental and calculated data verified high spin Ni(II), Co(II) and Mn(II) complexes and a bidentate binding through the carboxylic oxygen atoms (CCA2). The model calculations predicted pseudo octahedral trans-[M(CCA2)(2)(H(2)O)(2)] structures for the Zn(II), Ni(II) and Co(II) complexes and a binuclear [Mn(2)(CCA2)(4)(H(2)O)(2)] structure. Experimental and calculated (1)H, (13)C NMR, IR and UV-Vis data were used to distinguish the two possible bidentate binding modes (CCA1 and CCA2) as well as mononuclear and binuclear structures of the metal complexes.     

Global optimization based on novel heuristics,low-discrepancy sequences and genetic algorithms

In this paper a new heuristic hybrid technique for bound-constrained global optimization is proposed. We developed iterative algorithm called GLP_τS that uses genetic algorithms, LP_τ low-discrepancy sequences of points and heuristic rules to find regions of attraction when searching a global minimum of an objective function. Subsequently Nelder–Mead Simplex local search technique is used to refine the solution. The combination of the three techniques (Genetic algorithms, LP_τO Low-discrepancy search and Simplex search) provides a powerful hybrid heuristic optimization method which is tested on a number of benchmark multimodal functions with 10–150 dimensions, and the method properties – applicability, convergence, consistency and stability are discussed in detail.     

Mutual influence of Auger and non-radiative recombination processes under silicon femtosecond laser irradiation

The results of theoretical study of the contribution of recombination processes in additional heating of the surface of monocrystalline silicon during multipulse femtosecond laser processing are presented to discussion. The numerical evaluations are made in regimes of the laser radiation below the ablation threshold, when the microgeometry of the surface is formed due to the processes of self-organization. The influence of Auger recombination processes on the photoexcitation of the semiconductor during the pulse and relaxation after the pulse is studied in detail. It is shown that the additional heating of the surface due to non-radiative recombination is extremely small at pulse repetition rate 10 Hz–1 MHz. Mutual influence of recombination processes of both types is shown.     

SO（8）对关联和代数壳模型中的SU（3）四极基底（英文）

建立了SO（8） 同位旋标量、同位旋矢量及总的配对基与微观壳模型坐标空间部分的Elliott SU（3） 基之间的对应关系。从该代数间的互补关系导出了在壳模型的粒子数守恒代数U（4Ω） 中所包含的具有同位旋T 及自旋S 的Wigner 超多重态（不可约） 表示。其重要性在于,该结果能用于研究对相互作用和四极-四极相互作用在核谱中的竞争效应并揭示其配对基中的SU（3） 组份。虽然仅展示了该理论对ds 壳的计算,其方法也适用于研究多壳的情形。We establish a correspondence between the SO(8) isoscalar, isovector and total pairing bases and the Elliott's SU(3) basis in the algebraic structure of the spatial part of the microscopic shell model. It is derived from the complementarity of these algebras to the same T, S, (S,T) irreducible representations (irreps) of the Wigners supermultiplets, contained in the shell-model number-conserving algebra U(4Ω). This important result allows for the evaluation of the content of SU(3) irreps into the different types of pairing bases which leads to an investigation of the complementarity and competitive effects of pairing and the quadrupole-quadrupole interactions on the energy spectra of the nuclear systems. The theory is valid for any shell and for a number of shells as well, but we illustrate it with the results for a single ds-shell.     

Removal of cadmium and copper ions by <Emphasis Type="Italic">Trichosporon cutaneum</Emphasis> R57 cells immobilized onto polyvinyl alcohol/tetraethoxysilane hybrid matrices

Polyvinyl alcohol (PVA) and tetraethoxysilane (TEOS) hybrid materials were prepared by sol-gel methods and tested as matrices for immobilization of Trichosporon cutaneum R57, capable of removing cadmium and copper ions from aqueous solutions. A kinetic model was applied and the effects of matrix TEOS content on the copper and cadmium uptake equilibria and rate constants were investigated.      

Study of the nucleation and growth of TiO2 and ZnO thin films by means of molecular dynamics simulations

The nucleation and growth of titanium dioxide (TiO₂) and zinc oxide (ZnO) thin films on Fe₂O₃ (hematite), Al₂O₃ (α-alumina) and SiO₂ (α-quartz) are studied by molecular dynamics simulations. The results show the formation of a strong interface region between the substrate and the film in the six systems studied here. A combination of polycrystalline and amorphous phases are observed in the TiO₂ films grown on the three substrates. ZnO deposition on the Fe₂O₃ and Al₂O₃ crystals yields a monocrystalline film growth. The ZnO film deposited on the SiO₂ crystal exhibits less crystallinity. The simulation results are compared with experimental results available in the literature.