Development of the Pictet-Spengler reaction catalyzed by AuCl3/AgOTf

Mild and efficient AuCl3/AgOTf-catalyzed Pictet-Spengler reactions were developed to afford in good yields a variety of tetrahydroisoquinoline and tetrahydro-beta-carboline ring systems, which constitute important motifs in biologically active natural and synthetic organic compounds.     

Selective synthesis of monomeric or dimeric titanatranes via fine tuning in triethanolateamine ligand

Monomeric titanatrane i-PrOTi(OCMe₂CH₂)₃N (1) and dimeric titanatranes [i-PrOTi(OCH₂CH₂)_nN(CH₂CMe₂O)_3−n]₂ (n = 1, 2; n = 2, 3) were synthesized by the reaction of Ti(O-i-Pr)₄ with a series of triethanolateamines such as (OCH₂CH₂)_nN(CH₂CMe₂O)_3−n³⁻ (n = 0, Lig¹; n = 1, Lig²; n = 2, Lig³), which vary by the number of CMe₂ groups adjacent to a OH functionality from 3 (Lig¹H₃) to 2 (Lig²H₃) to 1 (Lig³H₃). The resultant titanatranes 1–3 have been characterized by solution ¹H and ¹³C{¹H} NMR and their solid state structures have been determined by X-ray crystallography. Whereas compound 1 is monomeric in the solid state, compounds 2 and 3 are dimeric, due to the reduction of the steric congestion in the vicinity of the Ti.     

Gold electroless deposition into poly-3,4-ethylenedioxythiophene films

By electroless deposition of gold into poly-3,4-ethylenedioxythiophene (PEDOT) films, the composite films (PEDOT-Au) are synthesized. Their electrochemical properties are studied by cyclic voltammetric (CVA) method. It is shown that in contrast to the original PEDOT film, the CVA curves of composite PEDOT-Au films measured in the presence of chloride ions reveal additional redox peaks associated with the presence of gold particles. The loading of metal gold particles by its chemical deposition into the polymer film is quantitatively assessed using quartz crystal microbalance method. The film mass is shown to depend on the time of gold loading and its original concentration in solution. The gold particles are shown to be oxidized by a reaction of the first order with respect to chloride ions. Based on the results of voltammetric and microbalance methods, the formation of a poorly soluble gold oxidation product Au(I)Cl in chloride-containing solutions was inferred.     

Determination of chromium(VI) in the soil organic fraction

A procedure was developed for determining chromium(VI) in the soil organic fraction; it consisted of three steps: the preparation of a soil solution; the isolation and separation of chromium(VI) and chromium(III); and the determination of chromium(VI). Soil solutions were prepared by leaching soil samples with a Na₄P₂O₇ solution (the Rudd method). Chromium(VI) was extracted from the soil solution with a solution of sodium diethyldithiocarbamate in n-amyl alcohol; the conditions of the extraction and separation of chromium(VI) and chromium(III) were optimized. Chromium(VI) in solutions was determined after back extraction by spectrophotometry with diphenylcarbazide or by flame atomic absorption spectrometry. The procedure was validated using a reference soil sample, and the material balance of chromium in the systems under study was calculated.     

Potential applications of fluorhydroxyapatite as biomaterials in medicine

The present work was undertaken to investigate the bioactivity and cytotoxicity of fluorhydroxyapatite ceramics. The bioactivity was evaluated by in vitro testing in simulated body fluid (SBF), in which ion concentrations are almost identical with inorganic ion concentrations of human blood plasma. Pellets of FA, HA and FHA were immersed in SBF for 48 hours, 1 week and 4 weeks at 36.5°C. Changes of the surface microstructure of the samples were observed by scanning electron microscopy (SEM). 48 hours and one week immersion in SBF did not result in any substantial progress in bioactivity. After 4 weeks in SBF a new biologically active layer was created on the surface of the biomaterials. In addition, the embryonal mouse fibroblast cell line NIH-3T3 was used for a comparative study of basal cytotoxicity of FHA, HA and FA discs. The sensitivity of these cells for tested biomaterials was evaluated on the basis of two cytotoxic end points: cell proliferation and cell morphology. The basal cytotoxicity of FHA, FA and HA discs was measured by a direct contact method. After 24, 48 and 72 hours, the cell growth was evaluated by direct counting of non-affected cells and cells treated by biomaterials. After 72 hours of biomaterials treatment, about 25% inhibition of cell number and unchanged morphology was found.      

Optimal pension fund management under multi-period risk minimization

In this paper, a multi-period stochastic optimization model for solving a problem of optimal selection of a pension fund by a pension plan member is presented. In our model, members of the pension plan are given a possibility to switch periodically between J types of funds with different risk profiles and so actively manage their risk exposure and expected return. Minimization of a multi-period average value-at-risk deviation measure under expected return constraint leads to a large-scale linear program. A theoretical framework and a solution for the case of the pension system of Slovak Republic are presented.     

Antihydrogen formation by autoresonant excitation of antiproton plasmas

In efforts to trap antihydrogen, a key problem is the vast disparity between the neutral trap energy scale ( $\sim\!50\,\upmu\mathrm{eV}$ ), and the energy scales associated with plasma confinement and space charge (~1 eV). In order to merge charged particle species for direct recombination, the larger energy scale must be overcome in a manner that minimizes the initial antihydrogen kinetic energy. This issue motivated the development of a novel injection technique utilizing the inherent nonlinear nature of particle oscillations in our traps. We demonstrated controllable excitation of the center-of-mass longitudinal motion of a thermal antiproton plasma using a swept-frequency autoresonant drive. When the plasma is cold, dense and highly collective in nature, we observe that the entire system behaves as a single-particle nonlinear oscillator, as predicted by a recent theory. In contrast, only a fraction of the antiprotons in a warm or tenuous plasma can be similarly excited. Antihydrogen was produced and trapped by using this technique to drive antiprotons into a positron plasma, thereby initiating atomic recombination. The nature of this injection overcomes some of the difficulties associated with matching the energies of the charged species used to produce antihydrogen.     

Process map for laser heat treatment of carbon steels

We propose a process map for diode-laser heat treatment of carbon steels. After first identifying a heat treatable region in terms of laser intensity and interaction time using a heat conduction model, two most important factors in heat treatment, carbon diffusion time in austenite and cooling time, are calculated and plotted in the heat treatable region. Because overall characteristics of laser heat treatment for a given steel type can be graphically visualized on a map, this map can be used in the determination of optimal process parameters. Hardening depth is also calculated using the concept of the critical effective carbon diffusion time. For demonstration and validation purposes, we have systematically conducted laser heat treatment on AISI 1020 and 1035 steel specimens using a 3 kW diode laser and measured surface hardness and hardening depth. The experimental results are in agreement with the calculated process map.     

A New Photoluminescent Conjugated Poly(1‐hexyl‐3,4‐dimethyl‐2,5‐pyrrolylene): Synthesis,Properties and Characterization

Oxidative coupling reaction of 1‐hexyl–3,4‐dimethylpyrrole affords a conjugated conducting poly(1‐hexyl‐3,4‐dimethyl‐2,5‐pyrrolylene) (PHDP), which is completely soluble in common organic solvents. The luminescence of PHDP is comparable to that of poly(N‐vinylcarbazole) (PVK), which has been widely used in electroluminescence devices. The quantum efficiency of PHDP is 2.5 times higher than that of PVK. A rationalization is presented relating the conductivity of PHDP to its polymer structure.