Sub-linear convergence of a stochastic proximal iteration method in Hilbert space

Computational Optimization and Applications - We consider a stochastic version of the proximal point algorithm for convex optimization problems posed on a Hilbert space. A typical application of...     

Dispersion and Interaction of Charged Fluorescent Dyes in Protein-Polymer Surfactant-based Non-Aqueous Liquid

Viscous, non-aqueous liquid comprising stoichiometric conjugates of polymer surfactant-bovine serum albumin (PSpBSA) is used as a host matrix for the dispersion of chemically distinct hydrophilic dyes. Using a combination of bright field polarized optical microscopy and fluorescence spectroscopy, we investigate the dispersion of dry and powdered cationic (Rhodamine 6G; Rh6G) and anionic (Fluorescein; FL) dyes in the PSpBSA liquid at room temperature. As the dyes disperse and dissolve in the PSpBSA liquid, it results in a pronounced increase in emission intensity of the former. Interestingly, a shift from 571 to 582 nm is observed in the emission maxima of Rh6G as it disperses in the PSpBSA solvent. Whilst no such red shift is found for the Rh6G dispersion in the aqueous solutions of either native BSA or polymer-surfactant conjugated BSA, a similar shift occurs when Rh6G is dispersed in neat polymer-surfactant (PS), suggesting the interaction of the dye with the PS chains. In the case of anionic FL, no shift is observed in its emission maximum as it disperses in the PSpBSA liquid. Furthermore, within 120 minutes of FL dispersion in the PSpBSA liquid, we observe a ≈26 % decrease in the tryptophan emission intensity (λ_exc.=285 nm; λ_emi.=330 nm) of BSA, which could be attributed to both static and dynamic quenching. Our findings provide a proof of concept of an alternative non-aqueous solvent matrix which can dissolve and disperse charged fluorescent dyes, provide suitable binding sites, and show substantial photoluminescence. Thus, it can be envisaged for utilization as an alternative solvent medium for lasing dyes and related applications.     

Novel Photosensitizers Based on Polysaccharides – Dextran Modified with Anthracene

Summary : Series of novel water-soluble photosensitizers based on dextran was synthesized and studied. Dextran was modified by covalent attachment of anthracene chromophores. Photophysical and photochemical properties of the photosensitizers in aqueous solutions were determined. Their applicability for sensitization of oxidation of polynuclear aromatics and degradation of pesticides was demonstrated. Removal of photosensitizers from the environment after their usage was discussed.     

Development of Carbazole and Bipyridine Copolymers as Novel Photovoltaic Materials

Summary: A novel acrylate polymer with a carbazole pendant group and bipyridine derivatives as side chains was synthesized, in which derivatives of bipyridine as electro-optic chromophores and carbazole as photoconductive moiety were covalently linked to the acrylate backbone. 2–(Carbazol-9-yl)ethyl methacrylate (CEM) and methacrylic 2-[5-(2-{5,5′-dimethyl-6′-[2-(5-pentylthiophen-2-yl)vinyl]-3,3′-bipyridin-6-yl}vinyl)thiophen-2-yl]ethyl methacrylate (BiPy) were synthesized and then copolymerized to give 99:1, 98:2, 92:8 (mol/mol) CEM/BiPy copolymers. Films of the copolymers blended with poly(3-octylthiophene) (P3OT) or poly(3-decylthiophene) (PDT) and sandwiched between the transparent ITO and Al electrode were examined for photovoltaic properties.     

Some Observations about the MOLSCAT

For calculation of cross sections for collisional transitions between rotational levels in a molecule, a computer code, MOLSCAT is available. For the transitions between rotational levels in H₂CS due to collisions with He atom, we have calculated cross sections under the CS approximation, for example, for total energy 11 cm^-1. The calculations have been done for the single energy 11 cm^-1 and for ten combinations. We have found that the cross sections for the single energy 11 cm^-1, differ from those in the first seven combinations, but are in agreement with those in the last three combinations. The reason for the difference in the results appears that the MOLSCAT uses the intermediate data of calculations for one energy, in the calculations for other energies. The agreement with the last three combinations may be understood that when the energy of combination is in the decreasing trend, the cross sections for the first (common) energy are equal. It may be suggested to run the MOLSCAT for a single energy at a time.     

Development and Validation of Stability Indicating LC Method to Quantify Captopril in Tablets of Controlled Release

An accurate, simple, reproducible, and sensitive liquid chromatographic method was developed and validated for the captopril determination in controlled release tablets. The analyses were performed at room temperature on a reversed-phase Phenomenex Luna C₁₈ column (250 mm × 4.6 mm). The mobile phase was composed of water:methanol (45:55; v/v) pH 2.5, and it was eluted isocratically at a 1.0 mL min⁻¹ flow rate. The method was validated in terms of specificity, linearity, quantification limit, detection limit, accuracy, precision and robustness. The response was linear in the range 0.3–1.5 mg mL⁻¹ (r ² = 0.9983). The relative standard deviation values for inter-and intra-day precision were 0.77% and 0.50%, respectively. Recoveries ranged between 97.7 and 99.1%. The method was successfully applied for the determination of captopril in the developed formulations.