Synthesis and characterisation of coating polyurethane cationomers containing fluorine built-in hard urethane segments

Polyurethane cationomers were synthesised in the reaction of 4,4’-methylenebis(phenyl isocyanate) with polyoxyethylene glycol (M?= 2,000) or poly(tetrafluoroethyleneoxide-co-difluoromethylene oxide) α,ω-diisocyanate and N-methyl diethanolamine. Amine segments were built-in to the urethane-isocyanate prepolymer in the reaction with 1-bromobutane or formic acid, and then they were converted to alkylammonium cations. The obtained isocyanate prepolymers were then extended in the aqueous medium that yielded stable aqueous dispersions which were applied on the surfaces of test poly(tetrafluoroethylene) plates. After evaporation of water, the dispersions formed thin polymer coatings. ¹H, ¹³C NMR and IR spectral methods were employed to confirm chemical structures of synthesised cationomers. Based on ¹H NMR and IR spectra, the factors κ and α were calculated, which represented the polarity level of the obtained cationomers. The DSC, wide angle X-ray scattering and atom force microscopy methods were employed for the microstructural assessment of the obtained materials. Changes were discussed in the surface free energy and its components, as calculated independently according to the method suggested by van Oss–Good, in relation to chemical and physical structures of cationomers as well as morphology of coating surfaces obtained from those cationomers. Fluorine incorporated into cationomers (about 30%) contributed to lower surface free energy values, down to about 15 mJ/m². That was caused by gradual weakening of long-range interactions within which the highest share is taken by dispersion interactions.     

Design, synthesis, and characterization of a calcium-sensitive near infrared dye

Intracellular calcium concentration in biological cells varies from 0.1 to 10 μM depending upon cell signaling and disease states. A direct estimate of calcium concentration in cell tissues within this range is possible with a novel calcium-selective reagent 15C5-774. The molecule of 15C5-774 consists of a near-infrared (NIR) chromophore (λ_max=774 nm) and a metal complexing moiety of benzo-15-crown-5. The reagent shows a strong calcium binding affinity in a 1:1 ratio and metal selectivity in the order Ca²⁺>Mg²⁺>Sr²⁺≈K⁺≈Na⁺>Zn²⁺>Li⁺. The high sensitivity is achieved by conducting absorption measurements in the NIR region where background interference from the biological matrix is low.     

Design and development of a fiber-optic immunosensor utilizing near-infrared fluorophores

The design and application of a fluorescent fiber-optic immunosensor (FFOI) are reported. The FFOI is utilized for the detection of antibody/antigen binding within the near-infrared (NIR) spectral region. The technique is developed through the combined use of fiber-optic, semiconductor laser-excitation, fluorescence detection, NIR dye, and immunochemical techniques. The antibody is immobilized on the FFOI and utilized as a recognition component for trace amounts of specific antigen. The FFOI is constructed to utilize an antibody sandwich technique. The assay involves the immobilization of the capture antibody on the sensing tip of the FFOI followed by the exposure of the immobilized sensing tip to the antigen. The antigen-coated FFOI is then introduced to a second antibody previously labeled with the NIR dye. Typical measurements are performed in about 15 min. A semiconductor laser provides the excitation (780 nm) of the immune complex. The resulting emission is detected by a silicon photodiode detector (820 nm). The intensity of the resulting fluorescence is directly proportional to the concentration of the antigen. The sensitivity of the analysis reaches 10 ng/ml and the response time is 10–15 min.     

Perturbational calculation of the exchange forces in the two lowest states of the hydrogen molecule

The interaction energies in the ground (X¹Σ) and the first excited (b³Σ)states of the hydrogen molecule were calculated using the modified Jansen and Byers Brown perturbation method. Calculations were performed for nine values of the internuclear distance R in the range 5 a.u. ≦ R ≦ 9 a.u. The present results were compared with the interaction energies calculated by four other perturbation methods as the expectation values of the H – E⁰ operator with the function accurate up to the first order. The results show that the method can give satisfactory values of the interaction energies.     

Cryopreservation of Prunus avium L. embryogenic tissues

Embryogenic tissues from wild cherry (Prunus avium L.) were successfully cryopreserved by using a one-step freezing procedure. Cryoprotection consisted of a pretreatment on solid medium with increasing sucrose concentrations (0.25 M for 1 day, 0.5 M for 1 day, 0.75 M for 2 days, and 1.0 M for 3 days), followed by air desiccation to about 20 percent moisture content (fresh weight basis). This method was compared with a pretreatment on solid medium containing 5 percent DMSO and 2 percent proline, followed by immersion in a modified PVS2 cryoprotective solution. Pretreatment on solid medium with increasing concentrations of sucrose led to regrowth of frozen embryogenic tissues, and after 6 weeks of culture, growth was comparable to that of non-dehydrated and non-frozen tissues. By contrast, no regrowth was observed when embryogenic tissues were submitted to the solid/liquid pretreatment with DMSO/proline and a modified PVS2 solution.     

Hydrotalcite-derived Co-containing mixed metal oxide catalysts for methanol incineration

The Co–Mg–Al mixed metal oxides were prepared by calcination of co-precipitated hydrotalcite-like precursors at various temperatures (600–800 °C), characterised with respect to chemical (AAS) and phase (XRD) composition, textural parameters (BET), form and aggregation of cobalt species (UV–vis-DRS) and their redox properties (H₂-TPR, cyclic voltammetry). Moreover, the process of thermal decomposition of hydrotalcite-like materials to mixed metal oxide systems was studied by thermogravimetric method combined with the analysis of gaseous decomposition products by mass spectrometry. Calcined hydrotalcite-like materials were tested as catalysts for methanol incineration. Catalytic performance of the oxides depended on cobalt content, Mg/Al ratio and calcination temperature. The catalysts with lower cobalt content, higher Mg/Al ratio and calcined at lower temperatures (600 or 700 °C) were less effective in the process of methanol incineration. In a series of the studied catalysts, the best results, with respect to high catalytic activity and selectivity to CO₂, were obtained for the mixed oxide with Co:Mg:Al molar ratio of 10:57:33 calcined at 800 °C. High activity of this catalyst was likely connected with the presence of a Co–Mg–Al spinel-type phases, containing easy reducible Co³⁺ cations, formed during high-temperature treatment of the hydrotalcite-like precursor.     

Exchange interactions in a trigonal chromium (III) pair

The theory of exchange interactions in the excited state of a trigonal chromium(III) pair which occurs in Cs₃Cr₂Cl₉, and first nearest neighbours in ruby, is extended to the singly excited ² T ₁, ² T ₂ and ² E(t ₂ ³) pair states. The multiplet splitting is described by an effective hamiltonian which includes trigonal field, spin-orbit coupling, first-order Zeeman effect and bilinear and biquadratic exchange. Previous calculations on the important single-ion intensity mechanism for ² E pair states are incorrect. The corrected electric dipoles for ² E and also for ² T ₁ and ² T ₂ pair states are presented.     

The temperature effect on the OH stretching vibration band of hydrogen bonded complexes

The temperature effect on the infrared spectra of hydrogen bonded systems has been analysed in terms of a stochastic model. Two different sources of this effect on protonic vibration bands have been shown. For weaker hydrogen bonds with an asymmetric potential energy curve the main factor seems to be a lowering of the average bridge length with decreasing temperature. Numerical results regarding the coefficient dν_OH/dT are in good agreement with experiment. In the case of moderately strong symmetric hydrogen bonds the main factor seems to be a population change of split tunnelling levels.     

The electronic spectrum of μ-oxo-bis[pentammine chromium(III)] ion

The single crystal polarized spectra of μ-oxo-bis[pentammine chromium(III)] chloride and perchlorate salts are measured over the temperature range 300 to 8 K. All sharp bands are predominantly z polarized where z is the CrOCr axis. The sharp and intense near ultraviolet absorptions are assigned as symmetric double excitations of t_2g electrons allowed through a vibronically exhange — induced electric dipole mechanism. This new mechanism can explain the observed z polarization, temperature-independent intensity and relatively high values of the oscillator strengths, f ≈ 10^?4?10^?3.The pair energies calculated from H= ∑_ikj1^Ja(ik)b(jl)⁵a(ik)^.5b(jl) do not agree with the observed values